Name of function cannot be exactly same as of name of other function or identifier within the scope of the function.

(1) What will be output of following c program?


#include<stdio.h>

int main(){

   int number,val;

   number=5<<2+5>>2;

   val=++number;

   val=number(val);

   printf("%d",val);

   return 0;

}

int number(int val){

   val=~val;

  return val;

}

Output: Compilation error

Explanation: number is function name as well as name of variable in the same scope.

(2) What will be output of following c program?


#include<stdio.h>

int main(){

    int val;{

      int number;

      number=5<<2+5>>2;

      val=++number;

  }

  val=number(val);

  printf("%d",val);

  return 0;

}

int number(int val){

  val=~val;

  return val;

}

Output: -162

Explanation:

First consider following expression: 5 << 2 + 5 >> 2

In above express there are three operators. They are: <<, +, >>

Among three + operator enjoy highest precedence. Hence first of addition operation will perform.

=5 << (5 + 2) >> 2

Now in << and >>, both have equal precedence. Hence associative will decide will which operator will execute first. Associative of shifting is LEFT to RIGHT. Hence, in the expression left shifting operator will execute first. So

= (5 * 2 ^7) >> 2

= (5 * 128)>>2

Now right shifting operator will execute.

640 >> 2

= 640 /(2 ^2)

= 640/4

= 160

So number = 160

Since val = ++number

so val = 161

Now we are passing 161 as function parameter.

val= ~val  

It is equivalent to

val = -(val+1)

val = -(161+1)

val= -162 



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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