Local variable and Global variable

Variable Scope

In variable chapter you have read about variable. There are two type of variable according to scope:
(1.) Local variable
(2.) Global variable

Local variable

A variable which is declared inside of function or block that is called "Local variable". Local variable can not be used outside of function or block. In below program a and b variable declared inside of f1() therefore a and b is local variable.

Program

#include <stdio.h>
#include <conio.h>

void f1(){
 int a = 100;
 int b = 200;
 printf("\n value of a = %d",a);
 printf("\n value of b = %d",b);
}

void main(){
 clrscr();
 f1();
 getch();
}

See Output

Program

#include <stdio.h>
#include <conio.h>

void f1(){
 int a = 100;
 int b = 200;
 printf("\n value of a = %d",a);
}

void f2(){
 printf("\n value of b = %d",b);
}

void main(){
 clrscr();
 f1();
 f2();
 getch();
}

See Output

In above program has an error and warning . In above program uses f1() and f2() function. Inside of f1() two variables is declared therefor a and b variable are local variable.

But f2() wants to use b variable therefore program has an error because local variable can not be use outside of function or block.

Program

#include <stdio.h>
#include <conio.h>

void f1(){
 int a;
 printf("\n enter value for a: ");
 scanf("%d",&a);
if(a > 0){
 int m;
 printf("\n Enter value for m: ");
 scanf("%d",&m);
 printf("\n value of a = %d ",a);
 printf("\n value of m = %d ",m);
}
}

void main(){
 clrscr();
 f1();
 getch();
}

See Output

In above program uses m variable which is declared inside of if(){ } block therefore m is local variable.

Program

#include <stdio.h>
#include <conio.h>

void f1(){
 int a;
 printf("\n enter value for a: ");
 scanf("%d",&a);
if(a > 0){
 int m;
 printf("\n Enter value for m: ");
 scanf("%d",&m);
}
 printf("\n value of a = %d ",a);
 printf("\n value of m = %d ",m);
}

void main(){
 clrscr();
 f1();
 getch();
}

See Output

In above program has error. f1() uses an if(){ } block. m varible is decalred inside of if(){ } block therefore m is a local variable.

But program uses m variable outside of if(){ } block therefore program has error because m variable can not be use outside of if(){ } block.

Program

#include <stdio.h>
#include <conio.h>

void f1(int m, int n){ 
 printf("\n value of m = %d",m);
 printf("\n value of n = %d",n);
}

void main(){
 clrscr();
 f1(100,200);
 getch();
}

See Output

parameter of a function is also called local variable. Therefore parameters can not be used outside of function.

Global Variable

Global variable is always declared outside of function body. Global variable can be use anywhere in program.

In below program n is declared outside of function therefore n is a global variable and global variable is used anywhere in program.

Program

#include <stdio.h>
#include <conio.h>

 int n = 100; /* global */
void f1(){
 printf("\n value of n = %d",n);
}

void f2(int a){
 printf("\n value of a = %d",a);
}

void main(){
 clrscr();
 f1();
 f2(n);
 getch();
}

See Output

Variable priority

Local variable and Global variable both are with same name then local variable priority is higher than global variable.

Program

#include <stdio.h>
#include <conio.h>

 int m = 100; /* global */

void f1(){
int m = 10; /* local */
 printf("\n value of m = %d",m);
}

void main(){
 clrscr();
 f1();
 getch();
}

See Output

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