Which bitwise operator is suitable for turning off a particular bit in a number?

In which stage the following code 
#include<stdio.h> 
gets replaced by the contents of the file stdio.h

 For which of the following, “PI++;” code will fail?

What is the output of the following program?

#include<stdio.h>
void main()
{
        printf(4+"TechEpi\t");
        printf("TechEpi"+4);
}

Point out the error in the program?

#include<stdio.h>
int main()
{
    struct a
    {
        float category:5;
        char scheme:4;
    };
    printf("size=%d", sizeof(struct a));
    return 0;
}

Which of the following are incorrect declarations?

Point out the error in the program?

typedef struct data mystruct;
struct data
{
    int x;
    mystruct *b;
};

What is the output of this C code?

  #include <stdio.h>
    union p
    {
        int x;
        float y;
    };
    int main()
    {
        union p p, b;
        p.x = 10;
        printf("%f\n", p.y);
    }

What is the output of the following program?

#include
void main()
{
        char c[]="gate2015";
        char *p=c;
        printf("%s",p+p[3]-p[1]);
}

What will the SWAP macro in the following program be expanded to on preprocessing? will the code compile?

#include<stdio.h>
#define SWAP(a, b, c)(c t; t=a, a=b, b=t)
int main()
{
    int x=10, y=20;
    SWAP(x, y, int);
    printf("%d %d\n", x, y);
    return 0;
}

What is the output of the program given below ?

#include<stdio.h>
int main()
{
    enum status { pass, fail, atkt};
    enum status stud1, stud2, stud3;
    stud1 = pass;
    stud2 = atkt;
    stud3 = fail;
    printf("%d, %d, %d\n", stud1, stud2, stud3);
    return 0;
}

Point out the error in the program?

struct emp
{
    int ecode;
    struct emp e;
};

What will be the output of the program?

#include<stdio.h>
#define MAN(x, y) ((x)>(y)) ? (x):(y);
int main()
{
    int i=10, j=5, k=0;
    k = MAN(++i, j++);
    printf("%d, %d, %d\n", i, j, k);
    return 0;
}

What will be the output of the program in DOS (Compiler - Turbo C)?

#include<stdio.h>
double i;
int main()
{
    (int)(float)(char) i;
    printf("%d", sizeof((int)(float)(char)i));
    return 0;
}