C Question of the Day -Preprocessor

1.What is the output of the following program?
#include<stdio.h>
#define PRODUCT(x) (x*x)
int main()
{
    int a=4,z;
    z=PRODUCT(a+1);
    printf("z=%d\n",z);
    return 0;
}
Solution

z=9
The expected output is 25. But the preprocessor replaces z=PRODUCT(4+1) as z=(4+1*4+1).* has higher preceddence than + . so the output is 4+4+1=>z=9

2.What is the output of the following program?
#include<stdio.h>
#define PRODUCT(x) (x*x)
int main()
{
    int a=4,x,y;
    x=PRODUCT(a++);
    y=PRODUCT(++a);
    printf("X=%d\t Y=%d\n",x,y);
    return 0;
}
Solution

X=16 Y=64

3.What is the output of the following program?
#include<stdio.h>
#define SEMI ;
int main()
{
    int x=4 SEMI ;
    printf("X=%d\n",x)SEMI
    return 0 SEMI
}
Solution

x=4
The program will not produce error.C statements should end with a semicolon. The compiler will take the 2nd  ; as a empty statement in line 5.

4.What is the output of the following program?
#include<stdio.h>
#define CHAR1 char
int main()
{
    typedef char CHAR2;
    CHAR1 x;
    CHAR2 y;
    x=255;
    y=255;
    printf("X=%d\tY=%d\n",x,y);
    return 0;
}
Solution

X=-1 Y=-1
default value of char is signed char.so the value above 127 are taken as the 2's complement value

5.What is the output of the following program?
#include<stdio.h>
#define SIZE sizeof(int)
int main()
{
    int i=-1;
    if(i<SIZE)
        printf("True\n");
    else
        printf("False\n");
    return 0;
}
Solution

False

6.What is the output of the following program?
#include<stdio.h>
#define SIZE(a) (&a+1) - &a
int main()
{
    float x;
    printf("X=%d\n",SIZE(x));
    return 0;
}
Solution

X=1