Dynamic Memory Management

Dynamic Memory Management

C programs can ask for memory while running, not just at compile time. That's dynamic memory.

Why dynamic memory?

• You don't always know at compile time how much you need.
• Arrays have fixed sizes; dynamic memory can grow on demand.
• Big structures need room beyond the stack.

The players

The functions live in <stdlib.h>:

malloc(size)     // allocate
calloc(n, size)  // allocate + zero
realloc(ptr, s)  // resize
free(ptr)        // release

The golden rule

Everything you allocate, you must eventually free. C does not clean up for you.

Include

#include <stdlib.h>

TL;DR

• Dynamic memory is allocated while running.
• malloc, calloc, realloc allocate; free releases.
• The lifecycle is manual in C - do not forget free.
• Allocation functions come from <stdlib.h>.