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Storage Classes in C

The document explains the four storage classes in C programming: Automatic, Register, Static, and External. Each class defines the scope, visibility, lifetime, and default value of variables, with examples provided for each. The Automatic class is the default for local variables, Register offers faster access, Static retains values after function exits, and External allows variable access across multiple files.

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7 views2 pages

Storage Classes in C

The document explains the four storage classes in C programming: Automatic, Register, Static, and External. Each class defines the scope, visibility, lifetime, and default value of variables, with examples provided for each. The Automatic class is the default for local variables, Register offers faster access, Static retains values after function exits, and External allows variable access across multiple files.

Uploaded by

v9r8rx9mnv
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Storage Classes in C

In C programming, a storage class defines the scope, visibility, lifetime, and default value of a
variable.
There are four storage classes in C:
1. Automatic (auto)
2. Register (register)
3. Static (static)
4. External (extern)

1. Auto Storage Class


- The 'auto' keyword is the default storage class for local variables.
- Variables are stored in the main memory (RAM).
- They have block scope and are automatically deallocated when the function exits.

#include <stdio.h>
void test() {
auto int x = 10; // Auto variable
printf("%d", x);
}
int main() {
test();
return 0;
}

2. Register Storage Class


- The 'register' keyword stores the variable in the CPU register instead of RAM.
- It provides faster access.
- Cannot use '&' operator to get the address of register variables.

#include <stdio.h>
int main() {
register int x = 5;
printf("%d", x);
return 0;
}

3. Static Storage Class


- The 'static' keyword retains variable value even after the function exits.
- The variable is initialized only once.

#include <stdio.h>
void counter() {
static int count = 0; // Static variable
count++;
printf("%d ", count);
}
int main() {
counter();
counter();
return 0;
}

4. External Storage Class


- The 'extern' keyword allows a variable to be accessed across multiple files.
- The variable is declared in one file and used in another.

// File 1: extern_var.c
#include <stdio.h>
int num = 10; // Global variable
// File 2: main.c
#include <stdio.h>
extern int num; // Accessing the global variable
int main() {
printf("%d", num);
return 0;
}

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