Preprocessor Directives | C Programming Questions and Answers | C Programming Free Online-Tests | LucentBlackBoard

01.

What is the output of following C code?
#define a 10
main()
{
#define a 50
printf("%d",a);
}

A.	50	B.	10
C.	15	D.	Error

Answer and Explanation

Answer: 50

Explanation:
The preprocessor directives can be redefined anywhere in the program. So the most recently assigned value will be taken.

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02.

What is the output of following C code?

#define clrscr() 100
main()
{
clrscr();
printf("%d\n",clrscr());
}

A.	100	B.	200
C.	Compiler Error	D.	null

Answer and Explanation

Answer: 100

Explanation:
Preprocessor executes as a separate pass before the execution of the compiler. So textual replacement of clrscr() to 100 occurs. The input program to compiler looks like this :
main()
{
100;
printf("%d\n",100);
}
Note:
100; is an executable statement but with no action. So it doesn't give any problem

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03.

What is the output of following C code?
#define f(g,g2) g##g2
main()
{
int var12=100;
printf("%d",f(var,12));
}

A.	100	B.	12
C.	112	D.	0

Answer and Explanation

Answer: 100

Explanation:
There is no explanation...

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04.

What is the output of following C code?

#define FALSE -1
#define TRUE 1
#define NULL 0
main() {
if(NULL)
puts("NULL");
else if(FALSE)
puts("TRUE");
else
puts("FALSE");
}

A.	Error	B.	NULL
C.	FALSE	D.	TRUE

Answer and Explanation

Answer: TRUE

Explanation:
Preprocessor doesn't replace the values given inside the double quotes. The check by if condition is boolean value false so it goes to else. In second if -1 is Boolean value true hence "TRUE" is printed.

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05.

What is the output of following C code?
#if something == 0
int some=0;
#endif

main()
{
int thing = 0;
printf("%d %d\n", some ,thing);
}

A.	0	B.	null
C.	0 0	D.	error

Answer and Explanation

Answer: 0 0

Explanation:
This code is to show that preprocessor expressions are not the same as the ordinary expressions. If a name is not known the preprocessor treats it to be equal to zero.

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06.

What will be output if you will compile and execute the following c code?
01 #include
02 #define x 5+2
03 int main()
04 {
05 int i;
06 i=x*x*x;
07 printf("%d",i);
08 return 0;
09 }

A.	343	B.	27
C.	133	D.	Compile Error
E.	None of above

Answer and Explanation

Answer: 27

Explanation:
There is no explanation...

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07.

In which header file is the NULL macro defined?

A.	stdio.h	B.	stddef.h
C.	stdio.h and stddef.h	D.	Math.h

Answer and Explanation

Answer: stdio.h and stddef.h

Explanation:
There is no explanation...

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08.

What will be the result of the following code?
#define TRUE 0
while(TRUE)
{
printf(“Wipro-BITS”);
}
printf(“BITS PILANI”);

A.	Wipro-BITS	B.	Nothing will be printed
C.	BITS	D.	BITS PILANI

Answer and Explanation

Answer: BITS PILANI

Explanation:
There is no explanation...

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09.

Referring to the sample below, what is MAX_NUM?
#define MAX_NUM 15

A.	MAX_NUM is an integer variable.	B.	MAX_NUM is a linker constant.
C.	MAX_NUM is a precompiler constant.	D.	MAX_NUM is a preprocessor macro.
E.	MAX_NUM is an integer constant.

Answer and Explanation

Answer: MAX_NUM is a preprocessor macro.

Explanation:
There is no explanation...

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