What is a pointer?

Learn that a pointer holds a memory address and is accessed with *.

What is a pointer?

A pointer is a variable that holds a memory address. The declaration int *ptr says ptr will hold the address of an int.

int x = 42;
int *ptr = &x;  /* & takes the address */
printf("%d\n", *ptr);  /* * accesses the value, prints 42 */

A pointer stores the memory address of a variable, not the variable itself. We will cover & and * in detail in the next lessons.

Pointer declaration syntax

A pointer declaration writes the type, the asterisk and the name together. The asterisk marks the variable as a pointer.

int *ip;     /* int pointer */
double *dp;  /* double pointer */
char *cp;    /* char pointer */

The pointer type depends on the type of the variable it points to. int * and char * are different types; they cannot be assigned to each other directly.

Exercise Access a value via a pointer

Define int x = 42;. Bind ptr to x with int *ptr = &x;. Print the value ptr points to with printf("%d\n", *ptr);. Output should be 42.

Show example solution

#include <stdio.h>

int main(void) {
    int x = 42;
    int *ptr = &x;
    printf("%d\n", *ptr);
    return 0;
}

Test yourself

What does int *ptr declare?
- ptr is an int value
- ptr is a constant
- ptr is a char
- ptr holds the address of an int
Show answer

ptr holds the address of an int — int *ptr declares that ptr holds the address of an int.

int pointer declaration

int ____ptr;  /* int pointer */

Show answer

int *ptr;  /* int pointer */

Match pointer types

int *

int pointer
char *

char pointer
double *

double pointer
void *

generic pointer

Next lesson: The & address operator

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