Name of function cannot be global identifier: Example

  

In c programming language name of function cannot be global identifiers. We function name will global identifiers then it will cause of compilation error.

(1) Program to find area of any circle.

#include <stdio.h>

#include <math.h>

float __radius__(float);

int main(){

   float r,a;

   printf("Radius of circle ");

   scanf("%f", &r);

   a=__radius__(r);

   printf("%f\n", a);

   return 0;

}

float __radius__(float r){

   float a;

   a = M_PI * r * r;

   return a;

}

Above program is valid in c language. But it is bad practice to write the function name like __radius__ since this format is used for global identifiers.

(2) Program to find LCM of any two numbers.

#include <stdio.h>

int main(){

   int n1,n2,lcm;

   printf("\nEnter two numbers:");

   scanf("%d %d",&n1,&n2);

   lcm=__TIME__(n1,n2);

   printf("L.C.M=%d",lcm);

   return 0;

}

int __TIME__(int n1,int n2){

   int x,y;

   x=n1,y=n2;

   while(n1!=n2){

      if(n1>n2)

        n1=n1-n2;

      else

        n2=n2-n1;

   }

   return x*y/n1;

}

Output: error

Explanation: Function name cannot be global identifier.

Definition of function in c
Name of function includes only alphabets, digit and underscore.
First character of name of any function must be an alphabet or underscore.
Name of function cannot be any keyword of c program.
Name of function cannot be global identifier.
Name of function cannot be exactly same as of name of function in the same scope.
Name of function is case sensitive
Name of function cannot be register Pseudo variable

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