Learn C Function by Example 4 : Function name cannot be same of identifier within the scope

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Invalid Example :

#include<stdio.h>
int sum(int,int);
int main()
{
   int sum,num1,num2;
   num1 = 10;
   num2 = 20;
   sum = sum(num1,num2);
   printf("Sum is : %d",sum);
   return 0;
}
int sum(int n1,int n2)
{
  return (n1+n2);
}

Output :

Compile Error

Explanation :

1. Consider following snippet

{
   int sum,num1,num2;
   num1 = 10;
   num2 = 20;
   sum = sum(num1,num2);
}

2. Opening and Closing curly braces is considered as one block.

Point 3 : Here inside same block we have two identifiers
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• “sum” as Variable name
• “sum” as Function name

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4. So it will cause confusion of compiler whether to treat “sum” as variable or function name.