Advanced · C PROGRAMMING

Dynamic memory allocation

What you will learn

Request memory and release it after use.

Understand the concept

calloc allocates storage for a requested number of elements and initializes the bytes to zero. Always check for allocation failure before accessing the result. free releases allocated storage. This example uses a small fixed count; for external sizes also check arithmetic bounds.

Read the example

The complete program appears below. Read it first, predict the output, then run it.

Expected output

Values: 12 0

Practise

Store three values, print their sum and keep exactly one free call for the allocation.

Common mistake

Do not use freed memory or free the same allocation twice. Returning early after allocation can leak memory unless you release it first.

Lesson discussion

#include <stdio.h>
#include <stdlib.h>

int main(void) {
    size_t count = 3;
    int *values = calloc(count, sizeof *values);
    if (values == NULL) return 1;
    values[0] = 12;
    printf("Values: %d %d\n", values[0], values[1]);
    free(values);
    values = NULL;
    return 0;
}

PRACTICE LAB

Read. Edit. Run.

C source · .c

Experiment with the program below. Your code and input are sent to the selected compiler only when you run it.

Compiler

C source

Tab indents · Shift+Tab unindents · Esc then Tab leaves the editor · Ctrl/Cmd+Enter runs · Ctrl/Cmd+S saves a draft

Changes save automatically to your account.

Standard input

Input / output example

Example input

No input required.

Expected output for the original program

Values: 12 0

Output will appear here.

Dynamic memory allocation

What you will learn

Understand the concept

Read the example

Expected output

Practise

Common mistake

Lesson discussion

Read. Edit. Run.

Input / output example

Debugging Lab

Interactive Memory Visualizer

Stack frames

Memory and pointers

Explore More from TCS Pune

Need help with your laptop or computer?