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.