C Storage Classes

C Storage Classes in C

In the C programming language, storage classes define the scope (visibility), lifetime (duration in memory), and linkage (access across files) of variables and functions.

There are four types of storage classes in C:

• auto
• register
• static
• extern

Let’s dive into each one in detail.

🔹 auto Storage Class

• It is the default storage class for variables declared inside a block (function or loop).
• Variables declared with auto are stored in memory (stack).
• Lifetime: Limited to the block.
• Scope: Local to the block.
• Linkage: None.

🔸 Example

#include <stdio.h>

void demo() {
    auto int x = 5;  // same as just `int x = 5;`
    printf("%d\n", x);
}


void count() {
    register int i;
    for (i = 0; i < 5; i++) {
        printf("%d ", i);
    }
}

void demo() {
    static int counter = 0;
    counter++;
    printf("Counter: %d\n", counter);
}

file1.C
int count = 100;

fil2.C
extern int count;

void show() {
    printf("Count is %d\n", count);
}