C Variable Scope

Variable scope is an area of a program where variables can be accessed.

Two types of variables depending on a variable scope.

• local scope variable aka. local variable
• global scope variable aka. global variables

Local variables

• The variable declared within parentheses of function or a block is called a local variable.
• These local variables are stored in stack section in memory.
• The scope and lifetime of a local variable are within the block/function.
• The default/initial value of a local variable is garbage.
• A local variable has higher priority than a global variable.

Output:

Global variables

The variables declare above the main() function are called as global variables

These global variables are stored in the data section of memory.

The scope and lifetime of a global variable are throughout the program.

The default/initial value of a global variable is zero.

The global variable should be initialized at the time of declaration.

Output:

Some more examples –

• A local variable has higher priority than a global variable.
  
  int a = 10; int main( ) { int a = 100; printf("a = %d ", a); }

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  int a = 10; int main( ) {     int a = 100;     printf("a = %d ",  a); }

  
  Output
  
  a = 100

  1

  a = 100

• Constant local variable should be initialized at time of declaration.
  
  int main( ) { const int a; a = 10; //error printf(" %d ", a); }

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  int main( ) {   const int a;     a = 10;                     //error   printf(" %d ", a); }

• The global variable should be initialized at the time of declaration.
  
  int a; a = 10; //not allowed int main() { printf(" %d ", a); }

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  int a; a = 10;                         //not allowed int main() { printf(" %d ", a); }