Introduction:
- We need to specify the storage class along with datatype in variable declaration.
- Storage class describes
- Memory location of variable
- Default value of variable
- Scope of variable
- Lifetime of variable
- Storage classes classified into
- Automatic Storage classes
- Register Storage classes
- Static Storage classes
- External Storage classes
| Syntax: storage_class datatype name ; Example: auto int a ; static int b ; |
Block scope of a variable:
- Defining a variable inside the block.
- We can access that variable from the same block only.
- We cannot access from outside of the block or from other block.
| #include<stdio.h> int main() { { int a=10; printf(“a val : %d \n”, a); } { int b=20; printf(“b val : %d \n”, b); printf(“a val : %d \n”, a); // Error : } return 0; } |
Function scope of a variable:
- Defining a variable inside the function.
- We can have number of blocks inside the function.
- Function scope variable can access throughout the function and from all block belongs to that function.
| #include<stdio.h> int main() { int a=10; /* function scope */ { int a=20; /* block scope */ printf(“Inside First block, a val : %d \n”, a); } { printf(“Inside Second block, a val : %d \n”, a); } printf(“Inside function, a val : %d \n”, a); return 0; } |
Note: If we don’t provide any value to local variable, by default the value is “Garbage value”
| #include<stdio.h> int main() { int a; { int a=10; printf(“a val : %d \n”, a); } { printf(“a val : %d \n”, a); } return 0; } |
Program scope:
- Defining a variable outside to all function
- We can also call it as Global variable
- We can access the global variable throughout the program.
| #include<stdio.h> void test(void); int a=10; /*program scope*/ int main() { int a=20; /*function scope */ { int a=30; /*block scope */ printf(“In block : %d \n”, a); } printf(“In main : %d \n”, a); test(); return 0; } void test() { printf(“In test : %d \n”, a); } |