C Linux interview questions and answers

(1)What will be output if you will execute following program by gcc compiler in Linux?

#include<stdio.h>

int main(){

    int a=5;

    printf("%d %d %d",a++,a++,++a);

    return 0;

}

Output:

In LINUX GCC compiler

7 6 8

In TURBO C

7 6 6

Hints: In Turbo c parameter is passed from right to left in printf function but not in the Linux.

(2)What will be output if you will execute following program by gcc compiler in Linux?

#include<stdio.h>

int main(){

    int a=5,b=10,c=15,d=20;

    printf("%d %d %d");

        return 0;

}

Output:

In LINUX GCC compiler

Garbage values

In TURBO C

5 10 15

Hints: Local variables stores in the stack.

(3) What will be output if you will execute following program by gcc compiler in Linux?

#include<stdio.h>

int main(){

    int i=5,j=5,y;

    int x=++i + ++i + ++i;

    y=++j + ++j + ++j;

    printf("%d  %d  %d %d",x,y,i,j);

    return 0;

}

Output:

In LINUX GCC compiler
22  22  8  8

In TURBO C

21  24  8  8

(4) What will be output if you will execute following program by gcc compiler in Linux?

#include<stdio.h>

int main(){

        int  near *p;

        int  far *q;

        int  huge *r;

        printf("%d  %d  %d",sizeof(p),sizeof(q),sizeof(r));

        return 0;

}

Output:

In LINUX GCC compiler

Compilation error

In TURBO C

2  4  4

Note: In Linux there is not any concept of near, far and huge pointers

(5) What will be output if you will execute following program by gcc compiler in Linux?

#include<stdio.h>

int main(){

    char *p;

    int *q;

    float **r;

    printf("%d  %d  %d",sizeof(p),sizeof(q),sizeof(r));

    return 0;

}

Output:

In LINUX GCC compiler

4  4  4

In TURBO C

2  2  2

Hints: size of any type of pointer in Linux is 4 and in turbo c is 2.

(6) What will be output if you will execute following program by gcc compiler in Linux?

#include<stdio.h>

int main(){

    short int a=5;

    int b=5;

    long int c=5l;

    float d=5.0f;

    double e=5.0;

    long double f=5.0L;

    char g='5';

    printf("Size of short int: %d\n",sizeof(a));

    printf("Size of int: %d\n",sizeof(b));

    printf("Size of long int: %d\n",sizeof(c));

    printf("Size of float: %d\n",sizeof(d));

    printf("Size of double: %d\n",sizeof(e));

    printf("Size of long double: %d\n",sizeof(f));

    printf("Size of char: %d\n",sizeof(g));

        return 0;

}

Output:
In LINUX GCC compiler

Size of short int: 2

Size of int: 4

Size of long int: 4

Size of float: 4

Size of double: 8

Size of long double: 12

Size of char: 1

In TURBO C

Size of short int: 2

Size of int: 2

Size of long int: 4

Size of float: 4

Size of double: 8

Size of long double: 10

Size of char: 1

(7) What will be output if you will execute following program by gcc compiler in Linux?

#include<stdio.h>

    int main(){

        int a=300;

    char *p=(char *)&a;

        printf("%d\n",*p);

    printf("%d",*++p);

        return 0;

}

Output:

In LINUX GCC compiler

44

1

In TURBO C

44

1

(8) What will be output if you will execute following program by gcc compiler in Linux?

#include<stdio.h>

int main(){

    char c='A';

    printf("%d   %d",sizeof(c),sizeof('A'));

    return 0;

}

Output:

In LINUX

1  4

In TURBO C

1  2

(9) What will be output if you will execute following program by gcc compiler in Linux?

#include<stdio.h>

int main(){

    enum color{RED,BLUE,GREEN=-2,YELLOW,PINK};

    printf("%d  %d",BLUE,PINK);

    return 0;

}

Output:

In LINUX GCC compiler

1 0

In TURBO C

1 0

(10) What will be output if you will execute following program by gcc compiler in Linux?

#include<stdio.h>

int main(){

    char c=127;

    printf("%d",++c);

    printf("  %d",++c);

    return 0;

}

Output:

In LINUX GCC compiler

-128 -127

In TURBO C

-128 -127

Hints: char data type cyclic property.

(11) What will be output if you will execute following program by gcc compiler in Linux?

#include"stdio.h"

struct info1{

    char *title;

    long int size;

    double grade;

}hero1;

union info2{

        char *title;

        long int size;

        double grade;

}hero2;

int main(){

    printf("Size of structure: %d\n",sizeof(hero1));

    printf("Size of union:  %d",sizeof(hero2));

    return 0;

}

Output:

In LINUX GCC compiler

Size of structure: 16

Size of union:  8

In TURBO C

Size of structure: 14

Size of union:  8

(12) What will be output if you will execute following program by gcc compiler in Linux?

#define size(x) (char *)(x+1)-(char *)x

#include<stdio.h>

int main(){

    long int *p;

    long double *q;

        printf("Size of long int: %d\n",size(p));

    printf("Size of long double: %d",size(q));

        return 0;

}

Output:

In LINUX GCC compiler

Size of long int: 4

Size of long double: 12

In TURBO C

Size of long int: 4

Size of long double: 10

(13) What will be output if you will execute following program by gcc compiler in Linux?

#include<stdio.h>

int main(){

      int i=2,j=5,k=3;

      int a=i&&j>=k;

      printf("%d",a);

      return 0;

}

Output:

In LINUX GCC compiler

1

In TURBO C

1

Hints: Any conditional or relational operator returns 1 if condition is true otherwise it returns 0.