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Variable naming rule questions in c


Following question are based on variable naming rules in c. If you have any doubt in the variable naming rules you can ask here.

Rules for identifiers in c language


1.

What will be output of the following c program?
#include<stdio.h>
int main(){
int goto=5;
printf("%d",goto);
return 0;
}

(A)5
(B)**
(C)**
(D)Compilation error
(E)None of these

Explanation:

Invalid variable name. goto is keyword in c. variable name cannot be any keyword of c language.

2.

What will be output of the following c program?
#include<stdio.h>
int main(){
long int 1a=5l;
printf("%ld",1a);
    return 0;
}

(A)5
(B)51
(C)6
(D)Compilation error
(E)None of these

Explanation:

Invalid variable name. Variable name must star from either alphabet or underscore.

3.

What will be output of the following c program?
#include<stdio.h>
int main(){
    int _=5;
    int __=10;
    int ___;
    ___=_+__;
    printf("%i",___);
    return 0;
}

(A)5
(B)10
(C)15
(D)Compilation error
(E)None of these
Explanation:

Variable name can have only underscore.

4.

What will be output of the following c program?
#include<stdio.h>
int main(){
    int max-val=100;
    int min-val=10;
    int avg-val;
    avg-val = max-val + min-val / 2;
    printf("%d",avg-val);
    return 0;
}

(A)55
(B)105
(C)
60
(D)Compilation error
(E)None of these

Explanation:

We cannot use special character – in the variable name.

5.

What will be output of the following c program?
#include<stdio.h>
int main(){
    int class=150;
    int public=25;
    int private=30;
    class = class >> private - public;
    printf("%d",class);
    return 0;
}

(A)1
(B)2
(C)4
(D)Compilation error
(E)None of these

Explanation:

Variable name can be keyword of c++.

6.

What will be output of the following c program?
#include<stdio.h>
int main(){
    int abcdefghijklmnopqrstuvwxyz123456789=10;
    int abcdefghijklmnopqrstuvwxyz123456=40;
    printf("%d",abcdefghijklmnopqrstuvwxyz123456);
    return 0;
}

(A)10
(B)40
(C)50
(D)Compilation error
(E)None of these

Explanation:

Only first 32 characters are significant in variable name. So compiler will show error: Multiple declaration of identifier abcdefghijklmnopqrstuvwxyz123456.

7.

What will be output of the following c program?
#include<stdio.h>
int main(){
    register xyz_123=91;
    auto pqr_123=991;
    const _1a1_=pqr_123+~xyz_123;
    printf("%d",_1a1_);
    return 0;
}

(A)900
(B)999
(C)899
(D)Compilation error
(E)None of these

Explanation:

Variable name can have digits.

8.

What will be output of the following c program?
#include<stdio.h>
int main(){
    int __SMALL__ = 11;
    int y;
    y= __SMALL__ < 5;
    printf("%d",y);
    return 0;
}

(A)11
(B)5
(C)0
(D)Compilation error
(E)None of these

Explanation:

Variable name cannot be global identifier.

9.

What will be output of the following c program?
#include<stdio.h>
int main(){
    int __BIG__ = 32;
    int y;
    y= __BIG__ && 8;
    printf("%d",y);
    return 0;
}

(A)
32
(B)8
(C)1
(D)Compilation error
(E)None of these

Explanation:

Variable name can be in the format: __NAME__. But it is bad practice since this format is used for global identifiers.

10.

What will be output of the following c program?
#include<stdio.h>
static num=5;
int num;
extern int num;
int main(){
    printf("%d",num);
    return 0;
}

(A)5
(B)10
(C)0
(D)Compilation error
(E)None of these

Explanation:

Two or more global variables can have same name but we can initialize only one of them.

11.

What will be output of the following c program?
#include<stdio.h>
static num=5;
extern int num;
int main(){
    printf("%d",num);
    return 0;
}
int num =25;

(A)
0
(B)5
(C)25
(D)Compilation error
(E)None of these

Explanation:

Two or more global variables can have same name but we can initialize only one of them.

12.

What will be output of the following c program?
#include<stdio.h>
static num;
int main(){
    printf("%d",num);
    return 0;
}
int num =25;

(A)0
(B)1
(C)25
(D)Compilation error
(E)None of these

Explanation:

Two or more global variables can have same name but we can initialize only one of them.

13.

What will be output of the following c program?
#include<stdio.h>
int xyz=10;
int main(){
    int xyz=20;
    printf("%d",xyz);
    return 0;
}

(A)10
(B)20
(C)30
(D)Compilation error
(E)None of these

Explanation:

Two variables can have same name in different scope.

14.

What will be output of the following c program?
#include<stdio.h>
int main(){
    int xyz=20;
    int xyz;
    printf("%d",xyz);
    return 0;
}

(A)20
(B)
0
(C)Garbage
(D)Compilation error
(E)None of these

Explanation:

Two local variables cannot have same name in same scope.

15.

What will be output of the following c program?
#include<stdio.h>
int main(){
    int xyz=20;{
         int xyz=40;
    }
    printf("%d",xyz);
    return 0;
}

(A)20
(B)
40
(C)
0
(D)Compilation error
(E)None of these

Explanation:

Two variables can have same name in different scope.

16.

What will be output of the following c program?
#include<stdio.h>
int main(){
    int main = 80;
    printf("%d",main);
    return 0;
}

(A)80
(B)
0
(C)
Garbage value
(D)Compilation error
(E)None of these

Explanation:

Variable name can be main.

17.

What will be output of the following c program?
#include<stdio.h>
int main(){
    struct a{
         int a;
    };
    struct a b={10};
    printf("%d",b.a);
    return 0;
}

(A)0
(B)
10
(C)Garbage value
(D)Compilation error
(E)None of these

Explanation:

Two variables can have same name in different scope.

18.

What will be output of the following c program?
#include<stdio.h>
int main(){
    int ABC=10;
    printf("%d",abc);
    return 0;
}

(A)10
(B)0
(C)5
(D)Compilation error
(E)None of these

Explanation:

Variable name is case sensitive.

19.

What will be output of the following c program?
#include<stdio.h>
int main(){
    int printf=12;
    printf("%d",printf);
    return 0;
}

(A)12
(B)
0
(C)5
(D)Compilation error
(E)None of these

Explanation:

Variable name cannot be pre defined function of included header file.

20.

What will be output of the following c program?
#include<stdio.h>
int main(){
    int EOF=12;
    printf("%d",EOF);
    return 0;
}

(A)12
(B)
0
(C)5
(D)Compilation error
(E)None of these

Explanation:

Variable name cannot be pre defined function of included header file.

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