C Programming C Preprocessor Online Test, C Programming MCQ

The preprocessor replaces the line #include <stdio.h> with the system header file of that name. More precisely, the entire text of the file ‘stdio.h’ replaces the #include directive.

The macro MAN(x, y) ((x)>(y)) ? (x):(y); returns the biggest number of given two numbers.

Step 1: int i=10, j=5, k=0; The variable i, j, k are declared as an integer type and initialized to value 10, 5, 0 respectively.

Step 2: k = MAN(++i, j++); becomes,

=> k = ((++i)>(j++)) ? (++i):(j++);

=> k = ((11)>(5)) ? (12):(6);

=> k = 12

Step 3: printf(“%d, %d, %d\n”, i, j, k); It prints the variable i, j, k.

In the above macro step 2 the variable i value is increemented by 2 and variable j value is increemented by 1.

Hence the output of the program is 12, 6, 12

The macro function SQUARE(x) x*x calculate the square of the given number ‘x’. (Eg: 10²)

Step 1: float s=10, u=30, t=2, a; Here the variable s, u, t, a are declared as an floating point type and the variable s, u, t are initialized to 10, 30, 2.

Step 2: a = 2*(s-u*t)/SQUARE(t); becomes,

=> a = 2 * (10 – 30 * 2) / t * t; Here SQUARE(t) is replaced by macro to t*t .

=> a = 2 * (10 – 30 * 2) / 2 * 2;

=> a = 2 * (10 – 60) / 2 * 2;

=> a = 2 * (-50) / 2 * 2 ;

=> a = 2 * (-25) * 2 ;

=> a = (-50) * 2 ;

=> a = -100;

Step 3: printf(“Result=%f”, a); It prints the value of variable ‘a’.

Hence the output of the program is -100

The macro function SQR(x)(x*x) calculate the square of the given number ‘x’. (Eg: 10²)

Step 1: int a, b=3; Here the variable a, b are declared as an integer type and the variable b is initialized to 3.

Step 2: a = SQR(b+2); becomes,

=> a = b+2 * b+2; Here SQR(x) is replaced by macro to x*x .

=> a = 3+2 * 3+2;

=> a = 3 + 6 + 2;

=> a = 11;

Step 3: printf(“%d\n”, a); It prints the value of variable ‘a’.

Hence the output of the program is 11

The macro function CUBE(x) (x*x*x) calculates the cubic value of given number(Eg: 10³.)

Step 1: int a, b=3; The variable a and b are declared as an integer type and varaible b id initialized to 3.

Step 2: a = CUBE(b++); becomes

=> a = b++ * b++ * b++;

=> a = 3 * 3 * 3; Here we are using post-increement operator, so the 3 is not incremented in this statement.

=> a = 27; Here, 27 is store in the variable a. By the way, the value of variable b is incremented by 3. (ie: b=6)

Step 3: printf(“%d, %d\n”, a, b); It prints the value of variable a and b.

Hence the output of the program is 27, 6.

The macro PRINT(int) print(“%d,”, int); prints the given variable value in an integer format.

Step 1: int x=2, y=3, z=4; The variable x, y, z are declared as an integer type and initialized to 2, 3, 4 respectively.

Step 2: PRINT(x); becomes printf(“int=%d,”,x). Hence it prints ‘int=2’.

Step 3: PRINT(y); becomes printf(“int=%d,”,y). Hence it prints ‘int=3’.

Step 4: PRINT(z); becomes printf(“int=%d,”,z). Hence it prints ‘int=4’.

Hence the output of the program is int=2, int=3, int=4.

The macro SWAP(a, b) int t; t=a, a=b, b=t; swaps the value of the given two variable.

Step 1: int a=10, b=12; The variable a and b are declared as an integer type and initialized to 10, 12 respectively.

Step 2: SWAP(a, b);. Here the macro is substituted and it swaps the value to variable a and b.

Hence the output of the program is 12, 10.

The following program will make you understand about ## (macro concatenation) operator clearly.

#include<stdio.h>
#define FUN(i, j) i##j

int main()
{
    int First  	= 10;
    int Second  = 20;

    char FirstSecond[] = "IndiaBIX";

    printf("%s\n", FUN(First, Second) );

    return 0;
}

Output:
-------
IndiaBIX

The preprocessor will replace FUN(First, Second) as FirstSecond.

Therefore, the printf(“%s\n”, FUN(First, Second) ); statement will become as printf(“%s\n”, FirstSecond );

Hence it prints IndiaBIX as output.

Like the same, the line printf(“%d\n”, FUN(va1, 2)); given in the above question will become as printf(“%d\n”, va12 );.

Therefore, it prints 20 as output.

The macro FUN(arg) prints the statement “IndiaBIX…” untill the while condition is satisfied.

Step 1: int i=2; The variable i is declared as an integer type and initialized to 2.

Step 2: FUN(i<3); becomes,

do
{
    if(2 < 3)
    printf("IndiaBIX...", "\n");
}while(--2)

After the 2 while loops the value of i becomes ‘0’(zero). Hence the while loop breaks.

Hence the output of the program is “IndiaBIX… IndiaBIX…”

The macro MAX(a, b) (a > b ? a : b) returns the biggest value of the given two numbers.

Step 1 : int x; The variable x is declared as an integer type.

Step 2 : x = MAX(3+2, 2+7); becomes,

=> x = (3+2 > 2+7 ? 3+2 : 2+7)

=> x = (5 > 9 ? 5 : 9)

=> x = 9

Step 3 : printf(“%d\n”, x); It prints the value of variable x.

Hence the output of the program is 9.

The macro MIN(x, y) (x<y)? x : y; returns the smallest value from the given two numbers.

Step 1: int x=3, y=4, z; The variable x, y, z are declared as an integer type and the variable x, y are initialized to value 3, 4 respectively.

Step 2: z = MIN(x+y/2, y-1); becomes,

=> z = (x+y/2 < y-1)? x+y/2 : y – 1;

=> z = (3+4/2 < 4-1)? 3+4/2 : 4 – 1;

=> z = (3+2 < 4-1)? 3+2 : 4 – 1;

=> z = (5 < 3)? 5 : 3;

The macro return the number 3 and it is stored in the variable z.

Step 3: if(z > 0) becomes if(3 > 0) here the if condition is satisfied. It executes the if block statements.

Step 4: printf(“%d\n”, z);. It prints the value of variable z.

Hence the output of the program is 3

The macro #define str(x) #x replaces the symbol ‘str(x)’ with ‘x’.

The macro #define Xstr(x) str(x) replaces the symbol ‘Xstr(x)’ with ‘str(x)’.

The macro #define oper multiply replaces the symbol ‘oper’ with ‘multiply’.

Step 1: char *opername = Xstr(oper); The varible *opername is declared as an pointer to a character type.

=> Xstr(oper); becomes,

=> Xstr(multiply);

=> str(multiply)

=> char *opername = multiply

Step 2: printf(“%s\n”, opername); It prints the value of variable opername.

Hence the output of the program is “multiply”

The macro PRINT(i) print(“%d,”, i); prints the given variable value in an integer format.

Step 1: int x=2, y=3, z=4; The variable x, y, z are declared as an integer type and initialized to 2, 3, 4 respectively.

Step 2: PRINT(x); becomes printf(“%d,”,x). Hence it prints ‘2’.

Step 3: PRINT(y); becomes printf(“%d,”,y). Hence it prints ‘3’.

Step 4: PRINT(z); becomes printf(“%d,”,z). Hence it prints ‘4’.

Hence the output of the program is 2, 3, 4.

The macro MAX(a, b, c) (a>b ? a>c ? a : c: b>c ? b : c) returns the biggest of given three numbers.

Step 1: int x; The variable x is declared as an integer type.

Step 2: x = MAX(3+2, 2+7, 3+7); becomes,

=> x = (3+2 >2+7 ? 3+2 > 3+7 ? 3+2 : 3+7: 2+7 > 3+7 ? 2+7 : 3+7)

=> x = (5 >9 ? (5 > 10 ? 5 : 10): (9 > 10 ? 9 : 10) )

=> x = (5 >9 ? (10): (10) )

=> x = 10

Step 3: printf(“%d\n”, x); It prints the value of ‘x’.

Hence the output of the program is “10”.

The macro #define SI(p, n, r) float si; si=p*n*r/100; contains the error. To remove this error, we have to modify this macro to

#define SI(p,n,r) p*n*r/100

The macros #ifdef #if #elif are called conditional macros.

The macro #undef undefine the previosly declared macro symbol.

Hence all the given statements are macro preprocessor directives.

True, #undef can be used only on a macro that has been #define earlier

Example: #define PI 3.14

We can undefine PI macro by #undef PI

True, We can prevent the same file from getting included again by using a preprocessor directive called #ifndef(short for “if not defined”) to determine whether we’ve already defined a preprocessor symbol called XSTRING_H. If we have already defined this symbol, the compiler will ignore the rest of the file until it sees a #endif (which in this case is at the end of the file).

#ifndef XSTRING_H

#define XSTRING_H defines the same preprocessor symbol,

Finally, the last line of the file, #endif

False, A macro just replaces each occurrence with the code assigned to it. e.g. SQUARE(3) with ((3)*(3)) in the program.

A function is compiled once and can be called from anywhere that has visibility to the funciton.

True, these macros are used for conditional operation.

#if <constant-expression>
#elif <constant-expression>
#endif