About C Pointer
In C programming, a pointer is a variable that stores the memory address of another variable.
Instead of holding a direct value, a pointer holds the address of a memory location where data is stored.
It is used to get the memory address of a variable.
It is also used to get the value at the memory location pointed to by a pointer.
It is used for more flexible and dynamic memory management.
Pointer Declaration & Initialization
To declare a pointer, an asterisk '*' also known as the dereference operator is used before the variable name (example: *pointer_Variable).
To get the memory address of a variable, the address-of operator (&) is used before the variable name (example: variable name number and memory address &number). Here is an example of declaring & initializing a pointer:
xxxxxxxxxxint number = 30;int *pointer_Variable = &number;Explanation of code:
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int number = 30;: This line declares an integer variable named 'number' and initializes the variable with value '30'. -
int *pointer_Variable = &number;: This line declares a pointer variable named 'pointer_Variable' (an asterisk '*' is used before the variable name) and initializes the variable with the memory address of 'number' variable by adding '&' (address-of operator) before the variable name (&number).
Get the Memory Address of a Variable Using a Pointer
The pointer variable hold the memory address of a variable as demonstrated in the following example:
Example of getting memory address of a variable using a pointer
xxxxxxxxxx#include <stdio.h>int main() { int number = 30; int *pointer_Variable = &number; printf("Address of number variable using pointer: %p\n", pointer_Variable); return 0; }Output of the above example
Address of number variable using pointer: 0028FF28
Please note that the memory address of a variable can vary in different pcs.
Explanation of code:
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int number = 30;: This line declares an integer variable named 'number' and initializes the variable with value '30'. -
int *pointer_Variable = &number;: This line declares a pointer variable named 'pointer_Variable' and initializes the variable with the memory address of 'number' variable&number. To get the memory address '&' is added with the 'number' variable. -
printf("Address of number variable using pointer: %p\n", pointer_Variable);: This line prints the address stored in 'pointer_Variable'. The format specifier '%p' is used to print the address stored in the pointer. '\n' creates a newline in C.
Get the Value of a Variable Using a Pointer
By using the dereference operator '*' before pointer variable, you can access the value stored at the address the pointer is pointing to as demonstrated in the following example:
Example of getting value of a variable using a pointer
xxxxxxxxxx#include <stdio.h>int main() { int number = 30; int *pointer_Variable = &number; printf("The value of number variable using pointer: %d\n", *pointer_Variable); return 0; }Output of the above example
The value of number variable using pointer: 30
Explanation of code:
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int number = 30;: This line declares an integer variable named 'number' and initializes the variable with value '30'. -
int *pointer_Variable = &number;: This line declares a pointer variable named 'pointer_Variable' and initializes the variable with the address of 'number' variable&number. -
printf("The value of number variable using pointer: %d\n", *pointer_Variable);: This line prints the value stored at the address the pointer is pointing to. The format specifier '%d' is used to print the integer data the pointer is pointing to.
Change the Value of a Variable Using a Pointer
You can change the value stored at the address the pointer is pointing to by assigning new value to the pointer as demonstrated in the following example:
Example of changing value of a variable using a pointer
xxxxxxxxxx#include <stdio.h>int main() { int number = 30; int *pointer_Variable = &number; *pointer_Variable = 50; printf("The new value of number variable using pointer: %d\n", *pointer_Variable); return 0; }Output of the above example
The new value of number variable using pointer: 50
Explanation of code:
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int number = 30;: This line declares an integer variable named 'number' and initializes the variable with value '30'. -
int *pointer_Variable = &number;: This line declares a pointer variable named 'pointer_Variable' and initializes the variable with the address of 'number' variable&number. -
*pointer_Variable = 50;: This line updates the variable value with new value '50' using pointer. Please note that the dereference operator '*' before pointer variable is used here. -
printf("The value of number variable using pointer: %d\n", *pointer_Variable);: This line prints the new value stored at the address the pointer is pointing to. The format specifier '%d' is used to print the integer data the pointer is pointing to.
