Chapter 1.2 Computer types Mainframes are powerful machines that allow companies to automate manual tasks, shorten marketing time for new products, use financial models that enhance profitability, and so on. The mainframe model consists of centralized computers that are usually housed in secure, climate-controlled computer rooms. End users interface with the computers through dumb terminals. These terminals are low-cost devices that usually consist of a monitor, keyboard, and a communication port to communicate with the mainframe. Personal computer (PC) is a standalone device. This means that it is independent of all other computers. A notebook that allow user to write and input data on its touch-screen is known as Table PC. Laptop, notebook, palmtop computers are classified as microcomputer. The reading/writing of digital data are represented by binary ‘0’ and ‘1’.
Chapter 1.4.1 Bus types Bus in a computer system is referred as an electronic pathway along which signals are sent from one part of the computer to another. There are three major system bus types that can be identified based on the type of information they carry. These include the address bus, data bus, and control bus. The address bus is a unidirectional pathway. Unidirectional means that information can only flow one way. The function of the pathway is to carry addresses generated by the CPU to the memory and I/O elements of the computer. The number of conductors in the bus determines the size of the address bus. The size of the address bus determines the number of memory locations and I/O elements that the microprocessor can address. The data bus is a bidirectional pathway for data flow. Bidirectional means that information can flow in two directions. Data can flow along the data bus from the CPU to memory during a write operation, and data can move from the computer memory to the CPU during a read operation. However, should two devices attempt to use the bus at the same time, data errors will occur. Any device connected to the data bus must have the capability to temporarily put its output on hold when it is not involved in an operation with the processor. This is also called a floating state. The data bus size, measured in bits, represents the computer word size. Generally, the larger the bus size is, the faster the computer system is. Common data bus sizes are 8-bits or 16-bits for older systems and 32-bits for new systems. 64-bit data bus systems are currently being developed. The control bus carries the control and timing signals needed to coordinate the activities of the entire computer. Control bus signals are not necessarily related to each other, unlike data and address buses. Some are output signals from the CPU, and others are input signals to the CPU from I/O elements of the system. Every microprocessor type generates or responds to a different set of control signals.
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Chapter 1.4.2 CPU The CPU contains two basic components, a control unit and an Arithmetic/Logical Unit (ALU). A control unit instructs the computer system on how to follow the program instructions. It directs the movement of data to and from processor memory. The control unit temporarily holds data, instructions, and processed information in its arithmetic/logic unit. In addition, it directs control signals between the CPU and external devices such as hard disks, main memory, and I/O ports. The Arithmetic/Logic Unit (ALU) performs both arithmetic and logical operations. Arithmetic operations are fundamental math operations like addition, subtraction, multiplication, and division. Logical operations such as the AND, OR, and XOR are used to make comparisons and decisions. Logical operations determine how a program is executed.
Chapter 1.4.4 Identifying SIMMs and DIMMS A SIMM plugs into the motherboard with a 72-pin or 30-pin connector. The pins connect to the system bus, creating an electronic path through which memory data can flow to and from other system components. Two 72-pin SIMMs can be installed in a computer that supports 64-bit data flow. With a SIMM board, the pins on opposite sides of the module board are connected to each other forming a single row of contacts. A DIMM plugs into the system memory bank using a 168-pin connector. The pins establish a connection with the system bus, creating an electronic path through which data can flow between the memory chip and other system components. A single 168-pin DIMM supports 64-bit data flow, for non-parity, and 72-bit data flow, for parity. This configuration is now being used in the latest generation of 64-bit systems. An important feature is that the pins on a DIMM board are not connected side to side, as with SIMMs, forming two sets of contacts. One difference between SRAM and DRAM is that DRAM is usually smaller in size. NOTE: SIMMs are available in 30-pin and 72-pin versions. DIMMs take the form of larger, 168pin circuit boards.
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Chapter 1.4.5 Modems A modem is the primary way to connect to the Internet with Windows 9x. A modem is a device that converts the digital data used by computers into analog signals, suitable for transmission over a telephone line, and converts the analog signals back to a digital signal at the destination. The word modem is actually an acronym for modulator/demodulator. A modem uses a dialup networking connection. A computer not connected to a network by some other means, such as a network interface card (NIC), will typically have a modem card installed. A modem plugged into one of the expansion slots inside a PC is known as an internal modem. Such a modem usually has two types of connectors called registered jack type 11. Registered jack type 11 is more commonly called an RJ-11 jack. One jack is for the phone line while the other is used to attach a traditional telephone handset. Modems come in the form of expansion cards, also known as modem cards. The modem card handles all the data transmission on the computer serial port with the help of a special chip. The chip is called the universal asynchronous receiver transmitter (UART) chip. Almost every PC sold today will have a 16550 UART chip inside. A 16550 UART chip is used because people want a high-speed connection to the Internet. The number 16550, represents a generational evolution of these chips.
Chapter 1.4.6 CD-ROM/DVD-ROM Drive A CD-ROM drive read speed determines the rate at which information can be pulled from the CD and sent to the communications bus. In general, the higher the read speed rating on a CD-ROM drive, the faster the drive. The read speed of a CD-ROM drive is measured in multiples of 150 kilobits per second (kbps) and denoted by a numeral followed by an x. A drive rated at 1x has a read speed of 150 kbps, or 1 times 150 kb. A drive rated at 10x has a read speed of 1500 kbps.
Harddisk Disk platters are the media on which data is stored in the hard disk drive. A hard disk drive typically has two to ten platters. They are usually either 2 ½" or 3 ½" in diameter and are typically constructed of aluminum or a glass-ceramic composite material. The platters are coated with a thin-film media that is magnetically sensitive. The platters are double-sided, with the magnetically sensitive media on each side. Platters are stacked with spaces between them on a hub that holds them in position, separate from one another. The hub is also called the spindle.
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SCSI disk types Three major versions of the SCSI standard are currently on the market. They are SCSI-1, SCSI-2, and SCSI-3. Installation of the three SCSI devices is similar. The differences are mainly in the size of the SCSI connector that is used to connect the SCSI disk drive to the SCSI cable. SCSI devices are typically connected in a series, forming chain that is commonly referred as a daisy chain. One advantage of SCSI as compared to IDE/EIDE is that it can connect more that two devices on one channel. The two SCSI devices at either end of the daisy chain must be terminated when using an external cable. Other devices do not need to be terminated. The SCSI bus identifies each device by a SCSI ID number. Most SCSI buses can handle a total of 7 devices and a SCSI controller per channel. The channels are numbered from 0 through 7. Some versions of SCSI support a total of 15 devices and a SCSI controller per channel. These channels are numbered 0 through 15. Each device on a SCSI channel must have a unique SCSI ID. Devices may include hard drives, CD-ROM drives, tape drives, scanners, and removable drives. Each SCSI device in the chain, including the SCSI controller card, is given a SCSI ID number from 0 to 7. The #0 is for the primary boot device, or hard drive. The #7 is for the SCSI controller card. In a SCSI system, all the read and write operations occur at the SCSI adapter memory buffer. Each device on a SCSI channel must have a unique SCSI ID. SCSI ID numbers do not have to be sequential. However, no two devices can have the same number, or else channel will become inaccessible. SCSI-1 SCSI-1, originally just known as SCSI, was used by many Apple computers in the early 1980s. By current standards it was slow. The SCSI bus ran at 5 MHz using an 8-bit data path. This allowed a data transfer rate of 5 MBps. SCSI-1 generally supported a single channel per SCSI controller. The SCSI-1 internal cable was a ribbon cable that was attached to the disk controller by a 50-pin connector. Many early SCSI controllers used a DB-25, 25pin connector, for external SCSI devices. The termination for the SCSI-1 was usually a set of 3 resistors on the SCSI controller if it was at the end of the SCSI bus. Two other possible terminations were a set of three resistors on the last SCSI disk drive on the bus, or an actual terminator attached to the end of the SCSI bus. Maximum cable length of SCSI-1 is 6 m. The maximum number of devices that be connected to a typical SCSI-1 controller card is 7. SCSI-2 SCSI-2 uses two different signaling systems. The systems are known as single-ended interface and differential interface. The two signaling systems are incompatible and cannot be mixed on the same SCSI bus. All devices, including the SCSI-2 controller, should use either the single-ended interface or all use the differential interface. Due to bus length restrictions, single-ended SCSI-2 cabling is usually found inside a server chassis. The differential interface allows for longer cable lengths. It is generally found connecting the server to an external SCSI device. SCSI-2 uses the same 50-pin connector on the internal SCSI cable that is used by SCSI-1 devices.
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SCSI-2 also has a variant called Wide SCSI-2. Wide SCSI-2 can transfer 16 bits at a time, as opposed to the 8 bits used by normal SCSI-1 and normal SCSI-2. This extra bus width requires the use of a 68-pin connector. Wide SCSI-2 allows for 16 devices on the SCSI-2 channel. Normal SCSI-2 and SCSI-1 only allow 8 devices on the SCSI channel. Normal SCSI-2 is also called narrow SCSI-2. Another variant of SCSI-2 is Fast SCSI-2. Fast SCSI-2 doubles the bus speed from 5 MHz to 10 MHz. Fast SCSI-2 requires an active termination technique. Due to the increased speed, the bus length is reduced from 6 m to 3 m. There is also a Fast-Wide SCSI-2 implementation. It requires 68-pin cables, active termination, and short cable length (3 m). However, it can transfer data at 20 MBps. Narrow SCSI-2 uses 50-pin connectors on the internal SCSI-2 devices. Wide SCSI-2 uses 68-pin connectors on the internal SCSI-2 devices. The Fast SCSI-2 and Fast-Wide SCSI-2 variants require active termination. Regular SCSI-2 and Wide SCSI-2 can use passive termination, although active termination is preferred. SCSI-3 SCSI-3 is the latest standard of the SCSI family. It combines all the best features of the previous SCSI standards. It uses LVD differential signaling and supports up to 15 devices on a single cable. The cable can be up to 12 m long. SCSI-3 supports three different bus speeds:
Ultra – 20 MHz Ultra2 – 40 MHz Ultra3 – Double-clocked 40 MHz
There are both narrow, 8-bit, and wide, 16-bit, implementations of the three SCSI-3 bus speeds. Ultra SCSI-3 and Ultra2 SCSI-3 both use 50-pin connectors. The wide variants, Wide Ultra SCSI-3 and Wide Ultra2 SCSI-3, use 68-pin connectors. Ultra3, Ultra160 SCSI-3, also use 68-pin connectors. All versions of SCSI-3 require active termination. SCSI-1, SCSI-2, and SCSI-3 disk drives can be mixed on the same SCSI channel, but it is not recommended. Mixing disk drives from the different versions of SCSI can seriously impact performance of the SCSI channel.
Chapter 1.6 Digital Cameras A digital still camera has a series of lenses that focus light to create an image of a scene just like a conventional film camera. It focuses light onto a semiconductor device that records the light electronically instead of focusing this light onto a piece of film. It is this electronic information that is broken down into digital data by the computer. This is what allows users to view, edit, email, and post pictures to the Internet. A charge-coupled device (CCD) is the image sensor used by many digital cameras. CCDs are used to capture and store image data in telescopes, scanners, digital still cameras, and digital video cameras. A good CCD can produce an image in extremely dim light, and its resolution does not degrade in low light the way those of film cameras do. Complementary metal oxide semiconductor (CMOS) technology is used by some of the more inexpensive
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cameras. Although CMOS sensors are improving all the time, the CCD technology will continue to be the standard in higher-end digital cameras. Resolution is measured in pixels. It is the amount of detail that the camera can capture. Basically, more pixels mean more detail and better quality. With low resolution, pictures will become grainy and look out of focus when enlarged. The following is a list of resolutions used by digital cameras:
256x256 pixels – This resolution is used on inexpensive cameras. It produces a low quality picture. This is 65,000 total pixels. 640x480 pixels – This resolution is a little better. This is an adequate resolution for e-mailing pictures and posting them on a Web site. This is 307,000 total pixels. 1216x912 pixels – This resolution is in the good range. It is enough to print images in addition to emailing and posting. This is a megapixel image size with 1,109,000 total pixels. 1600x1200 pixels – This is high resolution. Good results are achieved when printing to larger sizes like 8x10. This is almost 2 million total pixels.
Today, cameras with up to 10.2 million pixels are available, providing the same or even better results than film cameras. Many digital cameras use an LCD screen, which makes it possible to view and delete pictures right away. The next step is transferring them to the computer. This is accomplished in several different ways. Cameras with fixed storage must be connected to the computer in order to download the images. This connection can be by a serial, parallel, SCSI, or USB port. However, many newer cameras provide removable storage. This allows the images to be transferred to the computer or even directly to a printer without having to connect the camera. The following list describes storage systems:
Built-in memory – Built-in flash memory is used by many inexpensive cameras SmartMedia cards –Small Flash memory modules CompactFlash – Another form of Flash memory, similar to but slightly larger than SmartMedia cards Memory Stick – This is a proprietary form of Flash memory used by Sony Floppy disk – Some cameras can store images directly onto an inexpensive floppy disk Hard disk – Small built-in hard disks, or PCMCIA hard-disk cards, for image storage Writeable CD and DVD – Writeable CD and DVD drives to store images are used by higher-end cameras
A drive or reader is required to transfer files from Flash memory to a computer. These devices behave much like floppy drives and are inexpensive to buy. They allow images to be transferred to the computer without having to use cables. The difference between storage media is their capacity. A floppy disk is fixed while the capacity of Flash memory devices is increasing all the time.
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Digital cameras use two main file formats:
TIFF JPEG
JPEG is a compressed format and TIFF is an uncompressed format. The JPEG file format is used most often for storing pictures, providing different quality settings such as medium or high. Video cameras Video cameras or camcorders have been around for almost 20 years. They are similar to a digital camera in that they use CCD. The lens in a camcorder shines the light onto a CCD which measures light with a half-inch, or 1 cm, panel of 300,000 to 500,000 tiny lightsensitive diodes called photosites. There are two types of video cameras:
Analog Digital
Analog camcorders record video and audio signals as an analog track on video tape. Every time a copy of a tape is made, it loses some image and audio quality. Analog formats lack a number of the impressive features found in digital camcorders. The main difference between the available analog formats is what kind of video tape the camcorder uses and the resolution. Analog formats include the following:
Standard VHS – Uses the same type of video tapes as a regular VCR. Once recorded, they can be played on a standard VCR. VHS-C – This is a compact VHS format. The video camera tapes are smaller but can be played on a standard VCR with the use of an adapter. Super VHS – Super VHS tape records an image with 380 to 400 horizontal lines, a much higher resolution image than standard VHS tape. The video camera itself is a VCR and can be hooked up directly to a television or VCR to copy to standard VHS tapes. Super VHS-C – A more compact version of Super VHS that uses a smaller size cassette. 8mm – Small 8mm tapes, about the size of an audio cassette, are used and provide about the same resolution as standard VHS. The advantage is that this format allows for more compact video recorders, sometimes small enough to fit in a pocket. To view recordings, the video recorder is attached to the television. Hi-8 – Similar to 8mm camcorders, Hi-8 camcorders have a higher resolution, about 400 horizontal lines, and Hi-8 tapes are more expensive than ordinary 8mm tapes.
Digital recorders record information digitally, as bytes. This allows the image to be reproduced without losing any image or audio quality. Digital video can also be downloaded to a computer, where it can be edited or posted on the Internet. Also, digital video has a much better resolution than analog video, typically 500 horizontal lines. MiniDV These video recorders can be very small and lightweight. They record on compact cassettes, which are fairly expensive and hold about 60 to 90 minutes of footage. The recordings are at 500 lines of resolution and can be transferred to a personal computer. 7
They have the ability to capture still pictures, just as a digital camera does. Sony has recently introduced MicroMV, a format that works the same basic way as MiniDV but records on much smaller tapes. Digital8 Digital8 is produced by Sony exclusively. They are very similar to regular DV camcorders, but they use standard Hi-8mm tapes, which are less expensive and can hold up to 60 minutes of footage. Digital 8 recordings can be copied without any loss in quality and can be connected to a computer to download for editing or Internet use. DVD DVD video recorders are not as common compared to MiniDV models, but they will gain more acceptance. DVD recorders burn video information directly onto small discs. The advantage is that each recording session is recorded as an individual track, similar to the song tracks on a CD. These tracks make it possible to jump to any section of video. DVDs can hold 30 minutes to two hours of video. The newer DVD video recorders support two formats, DVD-R and DVD-RAM. DVD-R camcorder discs will work in most set-top DVD players. The disc can only be recorded to once. DVD-RAM makes it possible to record discs again and again, but they cannot be played in an ordinary DVD player. The video recorder is connected to the television to play or the movies can be copied to another format. Memory card Just like digital cameras, digital video recorders are available that record directly onto solidstate memory cards, such as Flash memory cards, Memory Sticks, and SD cards.
Chapter 1.7 Monitors/display devices Computers are usually connected to a display device, also called a monitor. Monitors are available in different types, sizes, and characteristics. When purchasing a new computer, the monitor may have to be purchased separately. Understanding the characteristics of a good monitor will help determine which is best suited for a specific system. The following terms relate to monitors.
Pixels – Picture elements. The screen image is made of pixels, or tiny dots. The pixels are arranged in rows across the screen. Each pixel consists of three colors. They are red, green, and blue (RGB). Dot Pitch – A measurement of how close together the phosphor dots are on the screen. The finer the dot pitch is, the better the image quality. Look for the smaller number. Most monitors today have a 0.25 mm dot pitch. Some have a 0.22 mm dot pitch, which gives a very fine resolution. Refresh Rate – The rate the screen image is refreshed. Refresh rates are measured in hertz (Hz), which means times per second. The higher the refresh rate, the more steady the screen image will be. It may look like a steady picture, but actually it flickers every time the electron beam hits the phosphor-coated dots. Refresh rate is also called vertical frequency or vertical refresh rate. Color Depth /Bit-Depth– The number of different colors each pixel can display. This is measured in bits. The higher the depth, the more colors that can be produced. 8
Video RAM (VRAM) – The memory a video card has. The more VRAM the video card has, the more colors that can be displayed. The video card also sends out the refresh signal, thus controlling the refresh rate. Resolution – Varies based on the number of pixels. The more pixels in the screen, the better the resolution. Better resolution means a sharper image. The lowest screen resolution on modern PCs is 640 x 480 pixels, which is called Video Graphics Array (VGA). There are now Super Video Graphics Array (SVGA) and Extended Graphics Array (XGA) with resolutions all the way up to 1600 x 1200. If you monitor is being overloaded by the output of the video card, you have to set the monitor to standard VGA settings of 640 x 480 pixels. Monitor screen sizes – Measured in inches. The most common sizes are 14", 15", 17", 19", and 21" screens, measured diagonally. Note that the visible size is actually smaller than the measurement size. Have this in mind when shopping for a monitor for the computer. Display Colors – The colors are created by varying the light intensity of the three basic colors. The 24- and 32-bit colors are the usual choice for graphic artists and professional photographers. For most other applications, a 16-bit color will be sufficient. The following is a summary of the most commonly used color depths: 256 colors – 8-bit color o 65,536 colors – 16-bit color, also called 65K or HiColor o 16 million colors – 24-bit color, also called True Color o 4 billion colors – 32-bit color, also called True Color
A high quality monitor and a high quality video card are required for both a high resolution and a high refresh rate.
Characterizing computer displays Computer video displays can be characterized according to the following characteristics:
Color capability Sharpness and viewability Size of the screen Projection technology
Color capability Today, most desktop displays provide color. Older notebook computers and smaller desktop computers sometimes have a less expensive monochrome display. The video displays can usually operate in one of several display modes. These modes determine how many bits are used to describe color and how many colors can be displayed. A display that can operate in Super Visual Graphics Array (SVGA) mode can display up to 16,777,216 colors because it can process a 24-bit long description of a pixel. The number of bits used to describe a pixel is known as its bit-depth. The 24-bit bit-depth is also known as true color. It allows eight bits 9
for each of the three additive primary colors red, green, and blue (RGB). Although human beings cannot really distinguish that many colors, the 24-bit system is necessary for graphic designers since it allocates one byte for each color. The VGA mode is the lowest common denominator of display modes. Depending on the resolution setting, it can provide up to 256 colors. Sharpness and viewability The absolute physical limitation on the potential image sharpness of a screen image is the dot pitch. The shape of this beam can be round or a vertical, slot-shaped rectangle depending on the display technology. Displays typically come with a dot pitch of .28 millimeters (mm) or smaller. This dot pitch is the diagonal distance between phosphor dots of the same color. The smaller the dot pitch, the greater the potential image sharpness. The actual sharpness of any particular display image is measured in dots-per-inch (dpi). The dpi is determined by a combination of the screen resolution, which is how many pixels are projected on the screen horizontally and vertically, and the physical screen size. A low resolution setting spread out over a larger screen will reduce sharpness. On the other hand, a high-resolution setting on a smaller surface will produce a sharper image, but text readability will become more difficult. Viewability is the ability to see the screen image from different angles. Displays with CRT generally provide good viewability from angles other than straight on. Flat-panel displays, including those using LED and LCD technology, are often harder to see at angles other than straight on. The size of the screen On desktop computers, the display screen width relative to height, known as the aspect ratio, is generally standardized at 4 to 3 (4:3). Screen sizes are measured diagonally from one corner to the opposite corner. They are measured in either millimeters or inches. Common desktop screen sizes are 15, 17, and 19 inches. Notebook screen sizes are somewhat smaller. Projection technology Many displays use Cathode Ray Tube (CRT) technology, which is similar to that used in most television sets. The CRT technology requires a certain distance from the beam projection device to the screen in order to function. Through the use of other technologies, displays can be much thinner. These displays are known as flat-panel displays. Flat panel display technologies include the following:
LED LCD Gas plasma
LED and gas plasma work by lighting up display screen positions based on the voltages at different grid intersections. LCDs work by blocking light rather than creating it. LCDs require far less energy than LED and gas plasma technologies and are currently the primary technology for notebook and other mobile computers. Displays generally handle data input as either character maps or bitmaps. In charactermapping mode, a display has a preallocated amount of pixel space for each character. In bitmap mode, a display receives an exact representation of the screen image that is to be projected in the form of a sequence of bits. This representation describes the color values for specific X and Y coordinates starting from a given location on the screen. Displays that handle bitmaps are also known as all-points addressable displays. 10
Chapter 3.3.2 Installing RAM Configuring Memory The motherboard manual will usually show the permissible combinations of DIMM types that can be installed in the system. New motherboards do not use SIMMs. It may be found, for example, that the DIMM sockets on the motherboard map are grouped into three or four banks of one slot each. Using the information provided, identify DIMM1 and DIMM2. DIMM1 and DIMM2 are Bank 0 and Bank 1. In some cases, motherboards have more than two slots for RAM. These slots would be DIMM3 and DIMM4 and the memory Banks are Bank 2 and Bank 3. Each bank can have any type of synchronous dynamic random access memory (SDRAM), which is the most commonly used form of RAM. It is recommend that the memory banks be filled in the exact combinations shown in the system board manual. For example, the manual might state that the maximum memory size is 512-MB and that the size of each DIMM can be 8-MB, 16-MB, 32-MB, 64-MB, or 128-MB. Any combination of these sizes can be used depending on memory needs. When DIMM sizes are mixed on the motherboard, it is important to remember to put the DIMM with the largest memory size in the first bank. The system automatically reads the size of the first DIMM and records it as the largest. If a smaller DIMM were put in the first bank, the system would read it as the largest and might fail to recognize or use the additional memory capacity of the DIMMs placed in the subsequent banks. Banking with SIMM modules is slightly different. Each bank of memory for a SIMM has two sockets. Users must fill the first bank before moving onto the next. Additionally, each bank must be filled with RAM modules that have the same access time and size. Step-by-Step Installation of RAM Step 1 First, decide on which slots to use and then orient the SIMM or DIMM chip over it. Both SIMMs and DIMMs are keyed, so they can only go in one way. Step 2 Insert the DIMM module straight into the slot. The SIMM module is inserted at an angle of about 45 degrees. Step 3 Now, the memory module must be locked into place. With a SIMM, rotate it from the angled position to the vertical position. Some resistance is normal. Do not force it. If difficulty is encountered, the chip might be backwards. Rotate it and try again. When the SIMM is vertical, the little metal or plastic clip should snap in place, securing the SIMM vertically in the memory slot. With a DIMM, simply close the levers on either side of it. If the levers do not close, it is usually because the DIMM is not inserted all the way into the slot or it is installed backwards. In most cases, if the DIMM is inserted properly, the levers will snap in place without further action. Step 4 Repeat Steps 1 to 3 for the rest of the memory modules. When finished, check the work to be sure that each module is well seated in the slot on both ends.
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Note: When using other types of memory modules such as Rambus inline memory modules (RIMMs) know that other considerations have to be taken into account. Unlike DIMMs and SIMMs, RIMM modules use only the direct Rambus memory chips (RDRAM). Some systems require that RIMM modules be added in identical pairs, and others allow single RIMMs to be installed. Information on specific memory types can be found in their manuals, the motherboard manual, or on the manufacturer websites.
Chapter 3.7.2 Connecting the Floppy Drive The following steps detail how to connect the floppy drive to the motherboard. Step 1 Identify the appropriate ribbon cable that goes with the floppy drive. It has a sevenwire twist towards one end and is smaller in width, 34-pins, compared to the 40-pin IDE ribbon cable. Step 2 Identify pin 1, the red edge of the cable, and align this with pin 1 on the rear of the floppy drive. Gently push on the cable connector until it is fully inserted. In most cases, the connectors are keyed. If any resistance is experienced as the cable is attached, then recheck the pin 1 alignment. Since this drive is being installed as drive A, be sure to use the connector past the twist in the cable. Step 3 Now identify the floppy controller on the system board by consulting the motherboard manual. Attach the connector on the far end of the ribbon cable to the floppy controller on the board. Make sure pin 1 is properly aligned for the cable and controller interface connectors. Step 4 Check work at this point, making sure that no pin is bent or displaced. If pin 1 has accidentally been reversed, the drive will not work and the drive light will stay on until it is corrected.
Adding hard disk Disk drive upgrades come in two varieties. The first type of upgrade involves adding disk drives to an existing network server, and the second type involves replacing existing disk drives with larger or faster disk drives. Upgrades to disk drives have the most potential of any upgrade to destroy data. Before attempting any disk drive upgrade, make sure that there is at least one, preferably two, verified full backups of the data on the disk drives. Upgrading ATA Hard Disk Drives This section describes how to upgrade ATA hard disk drives. To shorten the discussion, the term ATA refers to the following hard disk drives:
Integrated Device Electronics (IDE)/ATA Enhanced IDE (EIDE)/ATA with Extensions (ATA-2) Ultra ATA
The process is the same for all versions of ATA disk drives. Upgrades to ATA disks generally fall into two categories. They are adding disk drives 12
and replacing existing disk drives with faster or larger disk drives. Adding ATA disk drives to an existing ATA disk subsystem is relatively straightforward. ATA disk controllers generally have two channels to which ATA devices, such as disk drives, CD-ROM drives, and so on, can be attached. Each channel consists of a ribbon cable that can be up to 18 in. (46 cm) long, to which a maximum of two disk drives can be attached. One end of the channel is attached to the ATA disk controller, which may actually be built in to the system board. The channel, which is a 40-conductor ribbon cable, usually has two 40-pin connectors attached to it. These 40-pin connectors are used to attach ATA disk drives to the ATA channel. The ATA channels are usually labeled primary and secondary so that the system can distinguish between them. When only a single disk drive is attached to the ATA disk controller, a second disk drive can be attached in either of the two following ways:
The second disk drive can be attached to the same ribbon cable as the existing disk drive using the second 40-pin connector on the ribbon cable. In this case, one disk drive must be set to the master ATA disk role and the other must be set to the slave ATA disk role. Another method would be the user could set cable select (CSEL) for both disk drives. The second disk drive can be attached to the secondary ATA channel using a second ribbon cable for the ATA controller. Set this single drive to either the single drive or master ATA disk role depending on the manufacturer instructions for configuring a single disk drive on an ATA channel.
Putting the second ATA disk drive onto the secondary channel results in having one ATA disk drive on each ATA channel. Then performance of the disk subsystem can be enhanced. To set the master/slave configurations on 2 hard disks on the same channel, the jumper setting on the master hard disk is set to master, while the slave hard disk is set to slave.
Chapter 3.9.2 CMOS/BIOS errors The complementary metal oxide semiconductor (CMOS) or non-volatile random access memory (NVRAM) stores the system startup configuration and parameters. Common errors associated with the BIOS include Complementary Metal Oxide Semiconductor (CMOS) checksum errors, IRQ/DMA conflicts, hard drive errors, memory errors, and CPU problems. The BIOS is a good place to start diagnosing hardware problems. The features of BIOS provide technicians with low-level hardware and software configuration information. Most end users are not aware of BIOS information or they do not know how to interpret it, so it is rarely used effectively while troubleshooting. Checking the System BIOS When a computer or network server goes through power up, the version number of the system BIOS usually displays. Check the vendor website to determine whether the version of the system BIOS installed is the latest system BIOS available for the model computer. If a newer version of the system BIOS is available on the vendor website, download the upgrade 13
and follow the vendor instructions to update the system BIOS on the computer or network server. Most network servers and computers have a BIOS that is flashable, meaning that it can be easily erased and updated using software. Accessing the CMOS To access the CMOS setup utility, press the setup key during the boot process. The setup key must be pressed early in the boot process or the system will load the installed OS. If the video display is functional, a prompt to enter setup by pressing a certain key is usually displayed. The CMOS setup key is usually F1, F2, or Delete. However, there is no standard, so verify the setup key with the proper documentation. Identifying the Faulty or Incorrect CMOS Setting One way to help resolve CMOS related errors is to reset the CMOS settings to default. Resetting the CMOS clears the memory and all potentially corrupted data. Clearing the CMOS memory is useful when the computer will not boot. There are two ways to clear the CMOS memory. The easiest way is to remove the CMOS battery, which is the small round battery on the motherboard. Remove this battery as follows: 1. Turn off the power on the computer. 2. Remove the CMOS battery from the motherboard. 3. Short the negative and positive battery connections located on the motherboard using a conducting material such as a wire or a screwdriver head. 4. Replace the CMOS battery in its original position on the motherboard. 5. Turn the power on to reboot the system. If the above procedure fails to clear the CMOS, move the motherboard jumpers manually to the "Clear CMOS position" for a few seconds to clear the CMOS memory. To locate these jumpers, consult the motherboard documentation provided by the manufacturer. Upgrading the BIOS A BIOS upgrade can include patches, fixes, additional features and support for the latest devices to resolve any problems. If the system is operational, BIOS upgrades are risky and should be avoided. If the BIOS is updated incorrectly, it could damage the motherboard and peripheral devices. Special consideration must be taken before upgrading the BIOS. The motherboard is required to have flash BIOS, and it must support the upgraded version. The BIOS chip also needs to support the upgrade version number. Only when these criteria are met can the BIOS be successfully updated. Always obtain this information before attempting a flash BIOS upgrade. Generally, if the motherboard has PCI slots, it has flash BIOS. The BIOS revision number should display during startup. It will be in the format #401A0-1234. In this example, the revision number is 1234. It is the number that appears after the dash (-). The motherboard revision number will be printed on the motherboard. In newer motherboards, the revision number is located near the CPU or center of the motherboard. In order to upgrade the BIOS using flash, follow these general steps: 1. Obtain the latest BIOS program from the vendor, generally from the vendor website. 2. Follow the vendor instructions when loading the BIOS upgrade program onto a floppy disk drive. 3. Shut down and boot the computer or server, from the floppy disk containing the BIOS upgrade program and the latest BIOS. 14
4. Follow the onscreen instructions when performing the BIOS upgrade. 5. Never interrupt the flash BIOS upgrade process, because it could result in a computer or network server that cannot be booted. Upgrading Adapters To upgrade the BIOS or firmware on adapters, such as a SCSI adapter or a RAID controller, follow these general steps:
Locate the latest BIOS or firmware on the adapter vendor website. Download the BIOS or firmware upgrade and follow the vendor instructions to install the upgrade.
Chapter 3.9.1 Initializing the system hardware For an operating system to run, the system must be loaded into the computer RAM. When a computer is first turned on, it launches a program called the bootstrap loader that resides in the Basic Input Output System (BIOS) chip or firmware. The primary functions of the bootstrap loader are to test the computer hardware and to locate and load the operating system into RAM. Because the bootstrap program is built into the BIOS chip, it is also referred to as BIOS control. During the execution of the BIOS firmware routines, three sets of operations are performed: 1. Power-On Self Tests (POSTs) are run. 2. Initialization is completed. 3. BIOS moves the starting address and mode information into the DMA controller then loads the Master Boot Record (MBR). Power-On Self Test (POST) To test the computer hardware, the bootstrap program runs a program called power-on self test or POST. In this test, the computer CPU checks itself first and then checks the computer system timer. The POST checks the RAM by writing data to each RAM chip and then reading that data. Any differences indicate a problem. If the POST finds errors, it sends a message to the computer monitor. If the POST finds errors that cannot be displayed on the monitor, it sends errors in the form of beeps. If the POST does not find errors, the POST sends one beep and the screen begins to display OS loading messages.
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There are three major manufacturers of BIOS chips:
AMIBIOS, American Megatrends, Inc. PhoenixBIOS, Phoenix Technologies Ltd. AwardBIOS, Award Software, Inc., part of Phoenix Technologies
Each manufacturer has different beep codes. Different versions of the BIOS have different beep codes. It is normal to hear a single beep during the boot process, as long as the boot process does not stop. This is a code to signify that the computer is starting normally. POST is an important phase of the bootstrap process. Consult the manual that comes with the motherboard or the website of the manufacturer to learn more about the BIOS and the error beep codes.
Chapter 3.9.2 Booting the System for the first time Main option:
Date and Time – These first two fields are used for setting the clock that controls the settings in the operating system. The date and time are required for many types of software applications to manage data. The format required is very important. For the initial system setup, a default date is usually assigned, such as January 1, 1980. The time is given in the 24-hour format, similar to military time.
Hard Disks – This section contains fields that identify devices attached to the two IDE controllers integrated on the motherboard. IDE controllers can have up to two hard drives or one hard drive and another IDE device such as a CD-ROM. Normally, one is configured as a master and the other as a slave. There can be four configuration entries, including Primary Master, Primary Slave, Secondary Master, and Secondary Slave. It is usually recommended to set the drive type to Auto. This allows the BIOS to auto-detect and configure the hard drives so that this information does not have to be entered manually. The boot IDE hard drive should be at Primary Master.
Security Option: Passwords add security to a network system. The system administrator sets passwords for users and for the supervisor to manage the system.
User Password – This option allows the installation of a password that will prevent the system from booting unless the proper password is entered. This option also prevents access to the BIOS, eliminating the possibility of other people changing the BIOS setup on the computer. This option is particularly useful when booting up the computer for the first time. It is recommended to follow the on-screen and password instructions in the motherboard user manual. Supervisor Password – This feature is normally used only in large institutions where BIOS settings are kept standardized by computer support personnel. Once set, these computer BIOS setups are locked with a master password only known to
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the network administrator or an administrator designee. The instructions for this option can also be found in the motherboard manual. Boot sequence option:
Chapter 5.1.1 Disk Operating System (DOS) What is DOS, and why learn about it? Microsoft developed the Disk Operating System (DOS) in 1981. DOS, which is sometimes called MS-DOS, was designed for the IBM PC. Windows 98 and Windows 2000 both support DOS commands to reduce compatibility issues with older applications. DOS is a collection of programs and commands that are used to control overall computer operations in a disk-based system. There are three distinct sections that make up the disk operating system:
Boot files – These are used during the boot process, or system startup. File management files – These enable a system to manage its data in a system of files and folders. Utility files – These enable the user to manage system resources, troubleshoot the system, and configure the system settings.
DOS programs usually work in the background and allow the user to input characters from the keyboard, define a file structure for storing records on the disk, and output data to a printer or monitor. DOS is responsible for finding and organizing data and applications on the disk. The introduction of operating systems with GUIs, such as Microsoft Windows, has made DOS mostly obsolete. However, DOS is still important in many areas including programming, operating older applications, and installing Windows operating systems, especially on older computers. All generations of Windows support DOS commands for backward compatibility with older applications. It is important to understand the basics of DOS before proceeding with a Windows operating system installation.
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Basic Elements of DOS DOS is useful as a troubleshooting aid when Windows will not boot. It allows the hard drive to be accessed without the GUI and provides the ability to run troubleshooting or diagnostic programs. The following are some of the basic properties of DOS:
DOS is a command line operating system and it is not user-friendly. The best way to learn about DOS is to use it. DOS can only run one program at a time. It does not support multitasking. DOS can only run small programs and has memory limitations. DOS is an essential tool for IT professionals and is used extensively for troubleshooting.
To access DOS from Windows, click on Start > Run. A separate window opens that allows commands to be entered. Then type command to access the DOS prompt. DOS file structure To understand basic DOS commands, first look at the structure of the disk. Programs and data are stored on a disk the same way that a document would be filed in a file cabinet. Program and data files in DOS are grouped together in directories. Directories are similar to folders in a file cabinet. The files and directories are organized for easy retrieval and use. Directories can be kept inside other directories, just like a folder can be placed inside another folder. Nested directories are referred to as subdirectories. Directories are called folders in Windows operating systems. What Is a File? A file is a block of related data that is given a single name and treated as a single unit. Examples include programs, documents, drawings and other types of illustrations, and sound components. A record is kept of the location of every directory, subdirectory, and file on a disk. This record is stored on a table called the File Allocation Table (FAT). FAT32, which was introduced in Windows 95 OSR2, is an improved version of FAT. FAT32 allows a more efficient use of disk space for storing files. Files are referred to by filenames. In DOS, filenames can be up to eight characters with an extension of three characters. The extension, which identifies the file type, is separated from the main portion of the filename by a period (.). An example of a DOS file name is mynotes.txt. In DOS, all files have attributes, which are a set of parameters that describe a file. The nature of a file can be determined by the attributes of a file. The common attributes for DOS files include the following:
Hidden File – The user will not see hidden files when using a normal file search in a DOS environment. Read Only – The user can open and read this type of file but cannot modify the file in any way. Archive – The archive contains a backup copy of files. System File – The DOS operating system must have these files for a successful boot up. Hidden files are important files that must be concealed and protected from unauthorized users. A hidden file is not listed in a standard DOS directory listing and 18
it can only be seen with a specific command. It is important to note that a hidden file can still be accessed and modified. To see a hidden file, use the command dir /ah at a command prompt.
Directory Structures and Organization Hard drives organize the disk into directories and subdirectories. The main directory is called the root directory. All other directories branch out from the root directory, similar to the branches of a tree. In MS-DOS, a graphical representation of the directory organization is called a directory tree. It is important to understand how DOS organizes disks when preparing a hard drive for Windows installation. Finding a file requires knowledge of the drive, directory, and subdirectory in which the file is found. The first hard drive in most computer systems is C. Each hard drive in the computer can be thought of as a file cabinet or root. The root of the C drive is represented by C:\. Any files or directories within the root are represented by the root followed by the name of the file or directory, such as C:\example. Any directory or file located within a directory is represented by the directory name, followed by a backslash (\), followed by the name of the file or subdirectory, such as C:\example\file.exe. In MS-DOS, the format for specifying the path to a file is C:\directory\subdirectory \subdirectory\filename:
The C:\ specifies the C disk drive of the computer. The back slash (\) after each item signifies the presence of a directory or subdirectory. The first back slash indicates the root directory, which is present on all DOS disks. The filename, which is found at the end of the path, is located in the final subdirectory.
Overview of basic DOS commands A DOS command is an instruction that DOS executes from the command line. Internal commands such as dir and copy are built into the COMMAND.COM program and are always available when DOS is operating. Many external commands such as format and xcopy are individual programs that reside in the DOS directory. Internal versus External DOS Commands DOS contains internal commands, which are built into the operating system, and external commands, which must be executed from a file. Basic commands are generally internal and more advanced commands are usually external. External commands are stored on disk for future use. Internal commands are located in the COMMAND.COM program, and are loaded into memory during the boot up process. Examples of internal and external commands are discussed later in this module. What Is a Command Line? The operating system usually provides the user interface. In DOS, the main user interface is the command line. The command line is the space that follows the DOS prompt. For example, C:\ represents the hard disk drive root directory in C:\>. The greater-than sign (>) is called the prompt. All DOS commands are typed to the right of the prompt and are executed by pressing the Enter key. All DOS functions can be entered and executed from 19
the command line. For example, all system files in the C directory can be viewed by typing C:\>dir *.sys. Commonly Used DOS Commands and Switches DOS commands are used to instruct the disk operating system to perform a specific task. Many DOS commands can be modified by adding switches to the end. Switches are options that will modify the output of the command. A switch is added to the command by adding a space, a forward-slash (/), and a single letter. For example, C:\>dir /w. In this example, the /w is a switch. The /w will modify the dir command by presenting the screen output information in a wide format. The rest of this section will focus on some commonly used DOS commands and switches. The following commands are helpful for various operating system installations:
attrib – Used to display, set, or remove one or more of the four attributes that can be assigned to files and directories. The four attributes are read-only, archive, system, and hidden. The attrib command is an external DOS command. A plus (+) or minus (-) sign used in the attrib command sets or clears an attribute. The format of the attrib command is as follows: attrib [ + or - ] [variable] [directory\filename] /[switch] The following variables can be used with the attrib command: – r – Indicates a readonly file – a – Indicates an archive file – s – Indicates a system file – h – Indicates a hidden file del – This command deletes named files. The del and erase commands are synonymous. The switch /p is commonly used to prompt the user for confirmation before deleting each file. The format of the del command is as follows: del [directory\filename] /[switch] edit – This external command allows a user to view, create, or modify a file. The format of the edit command is as follows: edit [directory\filename] /[switch] The following switches are commonly used with the edit command: – b – Forces monochrome mode – h – Displays the maximum number of lines possible for the hardware – r – Loads files in read-only mode – [file] – Specifies initial files to load, wildcards and multiple file specs can be given format – This external command is used to erase all the information from a floppy disk or a hard drive. The format command can be used to prepare a hard drive before installing a Windows OS. A typical format command is as follows: format [directory\filename] /[switch] The following switches are commonly used with the format command: – q – Performs a quick format but does not clear the FAT so file recovery is possible – s – Copies system files to the formatted disk – u – Performs unconditional format and all previous data, including the FAT, is permanently erased Note: The /s switch must be added when formatting to make a system disk. If this switch is not used, the disk can be reformatted or the DOS sys command can be used. fdisk – This external command allows users to delete and create partitions on the hard disk drive. The fdisk command is commonly used to prepare the hard drive before installing a Windows OS. This command is entered at the command prompt as follows: fdisk /[switch] A commonly used switch is /status, it displays partition information when used with the fdisk command. scandisk – This command is a DOS program that is designed to detect and repair errors on a hard drive or floppy disk. The scandisk command is entered at the command prompt as follows: scandisk /[switch] Switches commonly used with the scandisk command are as follows: – all – Checks and repairs all local drives at once – checkonly – Checks the drive for errors but does not make repairs – autofix –
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Automatically fixes errors and saves lost clusters by default as files in the root directory mem – This external command is used to display a table that shows how memory is currently allocated. The mem command is entered at the command prompt as follows: mem /[switch] Switches commonly used with the mem command are as follows: – c – Lists the programs that are currently loaded into memory and shows how much conventional and upper memory each program is using – d – Lists the programs and internal drivers that are currently loaded into memory – e – Lists the free areas of conventional and upper memory, which are discussed later in this module – p – Pauses after each screen of information copy – This command is commonly used to copy one or more files from one location to another. The copy command can also be used to create new files. By using the copy con: command to copy files from the keyboard console to the screen, files can be created and then saved to disk. Switches commonly used with the copy command are as follows: – y – Replaces existing files without providing a confirmation prompt – -y – Displays a confirmation prompt before copying over existing files – a – Copies ASCII files and applies to the filename preceding it and to all following filenames – b – Copies binary files and applies to the filename preceding it and to all following filenames – v – Checks the copy to make sure that a file was copied correctly and displays an error message if the copy cannot be verified more – Displays output one screen at a time. The more command is entered at the command prompt as follows: more [filename]
The cd, mkdir, rmdir, and deltree commands are slightly different because they do not use switches. A brief description of these commands is as follows:
cd – Changes or displays the current directory on the specified drive mkdir or md – Creates a new directory rmdir or rd – Removes an empty directory, can only be used after all subdirectories and files within the directory have been deleted or moved deltree – Deletes a directory, including all files and subdirectories that are in it
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Creating a DOS boot disk There are times when computers will not be able to start. To troubleshoot the problem, an alternate method of starting the system is needed. A DOS boot disk is an important tool that is used to perform this task. DOS boot disks can also be used to boot up a newly assembled computer to install the operating system. The boot disk is a floppy disk with three necessary system files on it:
COMMAND.COM IO.SYS MSDOS.SYS
NOTE: The DOS boot disk may also contain a file called drvspace.bin. This file is only necessary to read a drive that has been compressed. The data on a compressed drive cannot be accessed without this file. Diagnostic programs should also be included on this disk. To create the boot disk, perform the following steps on a computer with DOS installed on the hard disk: Start the computer. Insert a blank floppy disk in the drive. Type format A: /s at the command prompt and press Enter. Type sys A: if the disk is already formatted and press Enter. Booting the system with a DOS Disk A DOS boot disk is used to boot a computer to the DOS prompt. The first section of a DOS disk contains the boot sector. The boot sector includes information about how the disk is 22
organized. Sometimes it contains a small master boot record (MBR) that can access a larger and more powerful bootstrap loader program, which is located in the root directory. The MBR is usually found at sector-1, head-0, and track-0 of the first logical hard drive or on the boot disk. The MBR is the required boot record on any boot or system disk. The MBR can boot up the hardware system to the operating system. A boot disk simplifies the process of preparing a hard drive and installing an operating system. Booting the System Insert a bootable disk in the floppy disk drive and turn on the computer. The BIOS will execute the bootstrap program, which is a small BIOS program that initiates and controls a large portion of the boot up process. The bootstrap program will move the MBR into RAM and then BIOS will begin loading the operating system. If the system performs a standard DOS boot up it will usually display the date and time prompts on the monitor screen, followed by the DOS command line prompt A:\. This prompt indicates that DOS is operational and that the A: floppy drive is the currently active drive. DOS Configuration Files In the MS-DOS operating system, there are two important configuration files called CONFIG.SYS and AUTOEXEC.BAT. These files can be included in the DOS boot up process. These files are used to optimize the system. At the beginning of the boot procedure BIOS checks the root directory of the boot disk for the CONFIG.SYS file. Then it searches for the COMMAND.COM interpreter. Finally, it looks in the root directory again for the AUTOEXEC.BAT file. The AUTOEXEC.BAT and CONFIG.SYS files can play important roles in optimizing the system memory and disk-drive usage. The order of file execution in the boot up process can be summarized as follows: 1. 2. 3. 4. 5.
IO.SYS MSDOS.SYS CONFIG.SYS COMMAND.COM AUTOEXEC.BAT
TIP: Test Tip: Remember the files involved in the DOS boot up process and the order of their execution. In Windows 9x, CONFIG.SYS is mostly needed for the installation of real-mode device drivers for devices that are not supported by Windows 9x 32-bit device drivers. Real-mode is discussed later in this module. CONFIG.SYS The CONFIG.SYS resides in the root directory and is used to load drivers and change settings at startup. Installation programs often modify CONFIG.SYS to customize the computer for their own use. Most CONFIG.SYS files in Windows 9x will be empty, plain text files that are waiting for any changes that the user wants to add to the system. After switching from DOS to Windows 9x, most of the values that were formerly located in this file will move to IO.SYS. To override the values in IO.SYS, enter the appropriate statements and values in CONFIG.SYS. CONFIG.SYS is also used to run memory managers.
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During the boot process, while the MS-DOS message "Starting DOS..." is on the screen, special function keys can be used to alter CONFIG.SYS. There is also an option to access AUTOEXEC.BAT:
F5 or the left Shift key – Skips CONFIG.SYS file including AUTOEXEC.BAT files F8 – Proceeds through the CONFIG.SYS files and any AUTOEXEC.BAT files one step at a time waiting for user confirmation
TIP: Test Tip: Know the function keys that can be used during the boot process. AUTOEXEC.BAT The AUTOEXEC.BAT contains DOS commands that will automatically be executed when DOS is loaded into the system. The following commands are normally located in the AUTOEXEC.BAT file:
DATE – Causes DOS to prompt the user for the date TIME – Causes DOS to prompt the user for the date and time PROMPT=$P$G – Causes the active drive and directory path to be displayed on the command line SET TEMP=C:\TEMP – Sets up an area for holding data temporarily in a directory called TEMP PATH=C:\;C:\DOS;C:\MOUSE – This command creates a specific set of paths that DOS uses to search for executable .COM, .EXE, and .BAT files. In this example, DOS will first search for executable files in the root directory of C, followed by the DOS directory, and finally the MOUSE directory. DOSKEY – Loads the DOSKEY program into memory SMARTDRV.EXE 2048 1024 – Configures the system for a 1-MB disk cache in DOS and a 2-MB cache for Windows CD\ – Causes the DOS default directory to change to the root directory DIR – Causes a DOS DIR command to be performed automatically It is important to know which commands are normally located in the AUTOEXEC.BAT file.
Editing system configuration files SYSEDIT is a standard text editor used to edit system configuration files such as CONFIG.SYS and AUTOEXEC.BAT. This utility can also be used to edit the Windows initialization files that are generally referred to as INI files. INI files are text files that users can edit with a standard text editor utility such as SYSEDIT. INI files were created when Windows 3.x was added to the DOS structure, and have been included in the \Windows directory of more recent Windows operating systems for backward compatibility. Common examples are WIN.INI and SYSTEM.INI. CONFIG.SYS and AUTOEXEC.BAT are found at the root directory C:\. To access these configuration files in Windows 95, choose Start > Run and type sysedit. These files can also be accessed for editing in MS-DOS by typing EDIT CONFIG.SYS or EDIT AUTOEXEC.BAT at the DOS command prompt.
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Chapter 5.1.2 Memory types
Conventional Memory Conventional memory includes all memory addresses between 0 and 640 KB. It is also called base memory. This is the area where MS-DOS programs normally operate. In older DOS machines, this is the only memory available for running the operating system files, application programs, memory-resident routines, and device drivers. Memory-resident routines include terminate-and-stay (TSR) programs such as mouse and CD-ROM drivers. Upper Memory and Expanded Memory Also known as reserved memory, upper memory includes memory addresses that fall between 640 KB and 1024 KB (1 MB). It follows conventional memory and has a size of 384 KB. Upper memory is available in the form of upper memory blocks (UMBs). Programs that operate on upper memory include system BIOS, plug-and-play BIOS, video BIOS, and video RAM. Depending on the system, between 96 KB and 160 KB of this memory space is not used by hardware, but these addresses are only available if an appropriate memory manager such as EMM386.EXE is installed during the startup process. Expanded memory is another memory area that is similar to upper memory. Expanded memory is also called the expanded memory specification (EMS). This memory that can be accessed in pages of 16-KB chunks from a 64-KB page frame. These pages are established in unused UMBs. The primary device driver that allows the use of EMS is the EMM386.EXE. This program frees up conventional memory by allowing unused portions of the reserved memory area to be used for DOS drivers and memory-resident routines.
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Extended Memory The 80286 microprocessor and its protected operating mode made it possible to access physical memory locations beyond the 1-MB limit of the 8088 and 8086 microprocessors. Memory above this address is generally referred to as extended memory. This area of memory is also called extended memory specification (XMS). XMS is the primary memory area used by Windows 9x. A device driver that is loaded by the operating system controls this memory area. Windows 9x loads the XMS driver called HIMEM.SYS during startup. HIMEM.SYS makes extended memory available to Windows 9x and other compatible MSDOS programs. If you have problem in loading HIMEM.SYS, your RAM may be faulty and you may need to replace it. High Memory After the XMS driver is loaded and extended memory becomes available to the operating system, the first 64 KB of extended memory is called the high memory area (HMA). HIMEM.SYS usually activates the DOS=HIGH option, which allows the MS-DOS kernel used by Windows 9x to be copied into the HMA. DOS uses the HMA, which frees up conventional memory for use by applications.
Chapter 5.6 Software utilities ScanDisk – This utility is used to check the integrity of files and folders or to thoroughly check the system by scanning the disk for physical errors. Defrag – When a program in installed on a computer, it may be stored in more than one place on the hard drive. This is known as fragmentation. Fragmentation lowers the performance of a drive. This utility optimizes space on the hard drive to allow programs to execute faster. CHKDSK /f – This command is used to check the file system for errors and can be compared to the ScanDisk for Windows 2000 and XP. As shown in Figure , CHKDSK is a DOS application that runs on the command line. REGEDIT – The Registry is a database that holds configuration data about the hardware and environment of the PC. REGEDIT is a command used by advanced technicians. The Registry Editor is shown in Figure . It provides access to the Registry in a view similar to Windows Explorer. If anything is changed in the Registry, it could result in system errors or malfunctions. Changes cannot be undone, so extreme caution is advised when using this program.
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Chapter 7.1.3 Laser printer Drum of laser printer will be spoilt if exposed to light for long period of time. The below diagram shows the laser printing process.
Chapter 7.2.3. Adding printer Add Printer Wizard can be intiated in Windows2000 by the following steps: Got to Startsettings printersAdd Printer.
Chapter 8.10.3 DSL and Cable modems External DSL and cable modems are connected to the network interface card of the computer.
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Chapter 9.2.1 Types of Viruses It is important to recognize the different types of viruses and what they do: File Virus – This common virus will modify an existing program so that the use of a seemingly safe program will activate the virus. Boot Sector Virus – This kind of virus targets the boot sector of every floppy or hard disk. If the boot sector of the primary hard drive is infected, the virus will be activated every time the computer is started. Macro Virus – This type of virus utilizes the built-in macro programming languages in word processors. Macros are used for the automatic formatting of documents and can be quite useful. However, they can also be written to do mischievous or damaging things.
Chapter 11.4 Upgrading peripheral devices A peripheral device is any device that is not part of the core computer system, which includes the processor, memory, and the data bus. Peripheral devices can be either internal to the server chassis or external to the network server chassis. See Figure . Internal peripherals include such components as disk drives, CD-ROM drives, floppy disk drives, and network interface cards. Upgrading disk drives such as EIDE and SCSI is covered in the section 9.4.4, Adding hard drives, in this module. Replacing, upgrading, or adding internal peripherals such as a CD-ROM drive, a DVD-ROM drive, a ZIP drive, a tape drive, or a NIC requires the user to shut down the network server. To install the drives, follow the manufacturer installation instructions. To install the NIC, follow the manufacturer installation instructions after identifying an empty PCI slot into which the NIC will be installed. Be sure to download the latest drivers for the NIC from the website of the NIC vendor. Remember that some network servers will have peer PCI buses and the "data load" should be balanced among the buses. This requires some knowledge of which PCI slots are on which PCI bus, as well as the data load placed on the PCI bus by the adapters currently on each PCI bus. If the adapters are not plug-and-play, the user may have to configure the adapters with an interrupt request (IRQ), a direct memory access (DMA) channel, and input/output (I/O) address. The IRQ, DMA, and I/O address cannot conflict with any adapter already installed in the network server. As with all upgrades, be sure to follow the upgrade checklist. External peripherals are devices external to the network server chassis, such as printers, modems, monitors, keyboards, and mice. External devices such as printers and monitors might be hot-swappable. Other external devices might require that the network server be shut down before they can be upgraded. Follow the manufacturer installation instructions for external peripherals. As with all upgrades, be sure to follow the upgrade checklist.
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Chapter 12.2.4 Virtual memory Software called the Memory Manager or Memory Management Unit (MMU) creates virtual memory by swapping files between RAM and the hard disk drive. The hard disk drive space is manipulated to act like RAM. For windows 2000 professional, virtual memory file is known as pagefile.sys and has a default size typically set at 1.5 times the amount of system RAM. Control of Windows 95, 98, and ME virtual memory operations is established through the Control Panel > System > Performance tab.
Chapter 14.2.1 Serial, parallel, USB, SCSI, and network communication types Printers require a method of communicating with the computers they serve. Communication is accomplished through the ports on both the printer and the computer or network device. Communication can also be accomplished by using wireless technologies such as infrared signals. Most printers use serial, parallel, USB, and SCSI ports with the appropriate network cables to receive information from computers. Each of these types is described in the sections that follow. Serial Serial ports are usually found on dot matrix printers that do not require high-speed transfers of data. Serial data transfer moves single bits of information in a single cycle. Serial ports are D-shell ports that are categorized as being either male or female and also by the number of pins available for each port. Common serial cables include 9-pins on both ends, 25-pins on both ends, and a combination of the two. Usually, the ends of the printer cables are secured to the ports on the printer and PC with thumbscrews. The maximum length of serial cable is 50 feet (18 meters). Figure shows an RS-232 serial interface cable. Parallel Parallel printers that use parallel communication have faster data transfer rates than serial printers because parallel data transfer moves multiple bits of information in a single cycle. This provides a wider path for information moving to or from the printer. IEEE 1284 is the current standard for parallel printer cables. The maximum length for IEEE 1284 cables is 3 meters (15 feet). Other standards such as Enhanced Parallel Port (EPP) and Enhanced Capabilities Port (ECP) allow bi-directional communication across the parallel cable. Parallel printer cables have two unique ends. Figure 1 shows a 1284 Type-A 25-pin DB 25 connector. The Type-A connector connects to the PC or daisy-chained peripheral and has two screws that should be hand-tightened. Figure 2 shows a 36-conductor Centronics connector. The Centronics connector connects to the printer and should be secured in place with the port clips. SCSI Small Computer System Interface (SCSI) is a type of interface that uses parallel communication technology to achieve high data transfer rates. There are many types of SCSI. The most common are the following:
SCSI 1 or plain SCSI SCSI 2 or wide SCSI 29
SCSI 3 or fast SCSI
SCSI printers and computers require the proper cabling for the ports. These ports can be DB 50, Mini DB 50, and DB 68. All of these ports may be male or female. Figure shows the SCSI cable types and connectors. USB Universal Serial Bus (USB) is a very common communication type for not only printers but also other devices due to its speed and ease of setup. Newer operating systems offer plugand-play USB support. When a device is added to a computer system via USB, it is automatically detected, and the driver installation process begins. A USB cable is a four-wire cable that has two unique ends. The slimmer end connects to the PC. The wider end, which is square, connects to the printer. These ends are keyed so that they can only fit one way into each port. FireWire FireWire, also known as i.LINK or IEEE 1394, is a high-speed, platform-independent communication bus that interconnects digital devices such as digital printers, scanners, digital cameras, hard drives, and so on. Figure shows an example of FireWire. Developed by Apple, FireWire was designed to allow peripherals to seamlessly plug into a computer. It also allows a device such as printer to be hot-plugged. FireWire provides a single plug-andsocket connection on which up to 63 devices can be attached with data transfer speeds up to 400 megabits per second (Mbps). In the future, IEEE 1394 implementations are planned to replace and consolidate serial and parallel interfaces, such as Centronics parallel, RS232C, and SCSI. The first printers to be introduced with FireWire are just beginning to come on the market. Network Network printers are commonly used in the workplace because they act as shared resources for all users on the network. Users are not required to have their own printers. These printers have high-speed outputs and offer many options, such as LAN fax, duplex, and finishers. These printers will need printer server network card in order to connect to the network. Connecting a printer to the network requires the correct type of cabling that is compatible with the existing network. Most network printers ship with an RJ-45 interface for connection into an Ethernet network. Other connection options include Bayonet Neill-Concelman or British Naval Connectors (BNC) and Token Ring ports. The maximum length of a Category 5 cable to connect a printer to the network is 328 feet (100 meters). Infrared Current wireless printing technology is built upon infrared technology, which uses a spectrum of light invisible to the human eye. For infrared communication to take place between a printer and a computer, transmitters and receivers are required on both devices. When setting up an infrared printer, there must be a clear line of sight between the transmitters and receivers on both devices with a maximum distance of 4.5 meters (15 feet).
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Figure 1
Figure 2
Chapter 14.3 Configuring printer sharing Printer sharing allows multiple users or clients to access a printer directly connected to a single computer, which is the print server. Sharing resources, like printers, was one of the reasons why networks were developed. A group of users sharing a single printer is far more economical than buying each user an individual printer. For print sharing to work, special software must be installed and configured on the print server. Then the clients must be configured to be able to access the printer located on the print server. While thirdparty software applications are available, most personal computer operating systems have printersharing capability built-in. In Windows, this option is called File and Print Sharing. While Windows 2000 installs this component automatically, it is easily added to the rest of the Windows operating systems. To install File and Print Sharing or to verify that it is installed on a Windows 9x computer, right-click on My Network Places in Windows ME or Network Neighborhood in Windows 95/98 and choose Properties. The window shown in Figure will display. The user can verify if File and Printer Sharing for Microsoft Networks is installed. If it is not installed, the user can easily do so by clicking the File and Print Sharing button and check either "I want to be able to give others access to my files.", or "I want to be able to allow others to print my from printer(s).", or both. Remember, the printer must be installed and configured on the print server before printer sharing will work. After verifying that the printer sharing software is installed, the server must know which printer it is going to share. In the Printers folder, right-click on the printer to share, choose Properties, and select the Sharing tab. Choose the option to share the printer and assign it a unique name. Finally, each client computer that will access the printer must have the correct printer drivers installed. Begin the Add Printer Wizard to find and install the shared printer. If configured properly, the client will automatically download the driver information from the server. NOTE: In a mixed operating system environment, compatible printers for each operating system are needed on the print server. Additionally, if there are different printers, the drivers for each individual printer must be put on the server.
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