Pointers

Memory 0x0

0x1

0x2

0x3

0x4

0x5

0x6

0x7

0x8

0x9

0xA

0xB

Creating Pointers Declaring pointers: * Examples: int* x; char* y; float* z;

Referencing and Dereferencing

Referencing: & Dereferencing: *

Under the hood...

int x = 5; int* ptr = &x; int copy = *ptr;

Variable

Address

Value

x

0x04

5

ptr

0x08

0x04

copy

0x0C

5

Track the values

x

ptr

int x = 5;

5

int* ptr = &x;

5

&x

*ptr = 35;

35

&x

Test Yourself a 1. 2. 3. 4. 5. 6. 7.

b

c

pa pb pc

Answers int a = 3, b = 4, c = 5; int* pa = &a, *pb = &b, *pc = &c;

a

b

c

pa pb pc

a = b * c;

20

4

5

&a

&b

&c

a *= c;

100

4

5

&a

&b

&c

b = *pa;

100

100

5

&a

&b

&c

pc = pa;

100

100

5

&a

&b

&a

*pb = b * c;

100

500

5

&a

&b

&a

c = (*pa) * (*pc);

100

500

10000

&a

&b

&a

50000

500

10000

&a

&b

&a

*pc = a * (*pb);

Pointer Arithmetic Adding/subtracting n adjusts the pointer by n * sizeof() bytes x

y

int x = 5;

5

int* y = &x;

5

0x04

y += 1;

5

0x08

What will print? int main(void) { char* str = "happy cat"; int counter = 0; for (char* ptr = str; *ptr != '\0'; ptr++) { counter++; } printf("%d\n", counter); }

Pointers and Arrays

int array[3]; *array = 1; *(array + 1) = 2; *(array + 2) = 3;

0

1

1

2

2

3

Pointers

0x0. 0x1. 0x4. 0x5. 0x6. 0x9. 0x8. 0xA. 0xB. 0x2. 0x7. 0x3. Memory. Page 3. Page 4. Creating Pointers. Declaring pointers: ... What will print? int main(void). { char* str = "happy cat"; int counter = 0; for (char* ptr = str; *ptr != '\0'; ptr++). { counter++;. } printf("%d\n", counter);. } Page 12. Pointers and Arrays int array[3];. *array = 1;.
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