Multiple choice questions in c



C programming language multiple choice questions and answers with explanation for interview

1.
What will be output if you will compile and execute the following c code?

void main(){
   int i=320;
   char *ptr=(char *)&i;
   printf("%d",*ptr);
}

(A) 320
(B) 1
(C) 64
(D) Compiler error
(E) None of above


Explanation:
As we know size of int data type is two byte while char pointer can pointer one byte at time.
Memory representation of int i=320

So char pointer ptr is pointing to only first byte as shown above figure.
*ptr i.e. content of first byte is 01000000 and its decimal value is 64.
Data type tutorial. 

2.

What will be output if you will compile and execute the following c code?

#define x 5+2
void main(){
    int i;
    i=x*x*x;
    printf("%d",i);
}

(A) 343
(B) 27
(C) 133
(D) Compiler error
(E) None of above


Explanation:
As we know #define is token pasting preprocessor it only paste the value of micro constant in the program before the actual compilation start. If you will see intermediate file you will find:
test.c 1:
test.c 2: void main(){
test.c 3: int i;
test.c 4: i=5+2*5+2*5+2;
test.c 5: printf("%d",i);
test.c 6: }
test.c 7:
You can absorb #define only pastes the 5+2 in place of x in program. So,
i=5+2*5+2*5+2
=5+10+10+2
=27
Preprocessor tutorial.

3.

What will be output if you will compile and execute the following c code?

void main(){
char c=125;
    c=c+10;
    printf("%d",c);
}

(A) 135
(B) +INF
(C) -121
(D) -8
(E) Compiler error


Explanation:
As we know char data type shows cyclic properties i.e. if you will increase or decrease the char variables beyond its maximum or minimum value respectively it will repeat same value according to following cyclic order:

So,
125+1= 126
125+2= 127
125+3=-128
125+4=-127
125+5=-126
125+6=-125
125+7=-124
125+8=-123
125+9=-122
125+10=-121

4.

What will be output if you will compile and execute the following c code?

void main(){
   float a=5.2;
  if(a==5.2)
     printf("Equal");
  else if(a<5.2)
     printf("Less than");
  else
     printf("Greater than");
}

(A) Equal
(B) Less than
(C) Greater than
(D) Compiler error
(E) None of above


Explanation:
5.2 is double constant in c. In c size of double data is 8 byte while a is float variable. Size of float variable is 4 byte.
So double constant 5.2 is stored in memory as:
101.00 11001100 11001100 11001100 11001100 11001100 11001101
Content of variable a will store in the memory as:
101.00110 01100110 01100110
It is clear variable a is less than double constant 5.2
Since 5.2 is recurring float number so it different for float and double. Number likes 4.5, 3.25, 5.0 will store same values in float and double data type.
Note: In memory float and double data is stored in completely different way. If you want to see actual memory representation goes to question number (60) and (61).
Data type tutorial.

5.

What will be output if you will compile and execute the following c code?

void main(){
  int i=4,x;
  x=++i + ++i + ++i;
  printf("%d",x);
}

(A) 21
(B) 18
(C) 12
(D) Compiler error
(E) None of above


Explanation:
In ++a, ++ is pre increment operator. In any mathematical expression pre increment operator first increment the variable up to break point then starts assigning the final value to all variable.
Step 1: Increment the variable I up to break point.

Step 2: Start assigning final value 7 to all variable i in the expression.


So, i=7+7+7=21
Operator tutorial.

6.

What will be output if you will compile and execute the following c code?

void main(){
 int a=2;
 if(a==2){
   a=~a+2<<1;
   printf("%d",a);
 }
 else{
  break;
 }
}

(A) It will print nothing.
(B) -3
(C) -2
(D) 1
(E) Compiler error


Explanation:
Keyword break is not part of if-else statement. Hence it will show compiler error: Misplaced break
Control statement tutorial

7.

What will be output if you will compile and execute the following c code?

void main(){
  int a=10;
  printf("%d %d %d",a,a++,++a);
}

(A) 12 11 11
(B) 12 10 10
(C) 11 11 12
(D) 10 10 12
(E) Compiler error


Explanation:
In c printf function follows cdecl parameter passing scheme. In this scheme parameter is passed from right to left direction.

So first ++a will pass and value of variable will be a=10 then a++ will pass now value variable will be a=10 and at the end a will pass and value of a will be a=12.
Function tutorial.

8.

What will be output if you will compile and execute the following c code?

void main(){
   char *str="Hello world";
   printf("%d",printf("%s",str));
}

(A) 11Hello world
(B) 10Hello world
(C) Hello world10
(D) Hello world11
(E) Compiler error


Explanation:
Return type of printf function is integer and value of this integer is exactly equal to number of character including white space printf function prints. So, printf(“Hello world”) will return 13.

9.

What will be output if you will compile and execute the following c code?

#include "stdio.h"
#include "string.h"
void main(){
   char *str=NULL;
   strcpy(str,"cquestionbank");
   printf("%s",str);
}

(A) cquestionbank
(B) cquestionbank\0
(C) (null)
(D) It will print nothing
(E) Compiler error


Explanation:
We cannot copy any thing using strcpy function to the character pointer pointing to NULL.
More questions of string.

10.

What will be output if you will compile and execute the following c code?

#include "stdio.h"
#include "string.h"
void main(){
  int i=0;
  for(;i<=2;)
   printf(" %d",++i);
}

(A) 0 1 2

(B) 0 1 2 3
(C) 1 2 3
(D) Compiler error
(E) Infinite loop


Explanation:
In for loop each part is optional.
Complete tutorial of looping in C.

11.

What will be output if you will compile and execute the following c code?

void main(){
  int x;
  for(x=1;x<=5;x++);
    printf("%d",x);
}

(A) 4
(B) 5
(C) 6
(D) Compiler error
(E) None of above


Explanation:
Body of for loop is optional. In this question for loop will execute until value of variable x became six and condition became false.
Looping tutorial.

12.

What will be output if you will compile and execute the following c code?

void main(){
printf("%d",sizeof(5.2));
}

(A) 2
(B) 4
(C) 8
(D) 10
(E) Compiler error


Explanation:
Default type of floating point constant is double. So 5.2 is double constant and its size is 8 byte.
Detail explanation of all types of constant in C.

13.

What will be output if you will compile and execute the following c code?

#include "stdio.h"
#include "string.h"
void main(){
char c='\08';
printf("%d",c);
}


(A) 8
(B) ’8’
(C) 9
(D) null
(E) Compiler error


Explanation:
In c any character is starting with character ‘\’ represents octal number in character. As we know octal digits are: 0, 1, 2, 3, 4, 5, 6, and 7. So 8 is not an octal digit. Hence ‘\08’ is invalid octal character constant.
Hexadecimal character constant.

14.

What will be output if you will compile and execute the following c code?

#define call(x,y) x##y
void main(){
int x=5,y=10,xy=20;
printf("%d",xy+call(x,y));
}

(A) 35
(B) 510
(C) 15
(D) 40
(E) None of above


Explanation:
## is concatenation c preprocessor operator. It only concatenates the operands i.e.
a##b=ab
If you will see intermediate file then you will find code has converted into following intermediate code before the start of actual compilation.
Intermediate file:
test.c 1:
test.c 2: void main(){
test.c 3: int x=5,y=10,xy=20;
test.c 4: printf("%d",xy+xy);
test.c 5: }
test.c 6:
It is clear call(x, y) has replaced by xy.
Preprocessor tutorial.

15.

What will be output if you will compile and execute the following c code?


int * call();
void main(){
int *ptr;
ptr=call();
clrscr();
printf("%d",*ptr);
}
int * call(){
int a=25;
a++;
return &a;
}


(A) 25
(B) 26
(C) Any address
(D) Garbage value
(E) Compiler error


Explanation:
In this question variable a is a local variable and its scope and visibility is within the function call. After returning the address of a by function call variable a became dead while pointer ptr is still pointing to address of variable a. This problem is known as dangling pointer problem.
Complete pointer tutorial.

16.

What is error in following declaration?

struct outer{
int a;
struct inner{
char c;
};
};

(A) Nesting of structure is not allowed in c.
(B)
It is necessary to initialize the member variable.
(C) Inner structure must have name.
(D) Outer structure must have name.
(E) There is not any error.


Explanation:
It is necessary to assign name of inner structure at the time of declaration other wise we cannot access the member of inner structure. So correct declaration is:
struct outer{
int a;
struct inner{
char c;
}name;
};
Union tutorial.

17.

What will be output if you will compile and execute the following c code?

void main(){
int array[]={10,20,30,40};
printf("%d",-2[array]);
}

(A) -60
(B) -30
(C) 60
(D) Garbage value
(E) Compiler error


Explanation:
In c,
array[2]=*(array+2)=*(2+array)=2[array]=30

18.

What will be output if you will compile and execute the following c code?

void main(){
int i=10;
static int x=i;
if(x==i)
printf("Equal");
else if(x>i)
printf("Greater than");
else
printf("Less than");
}

(A) Equal
(B) Greater than
(C) Less than
(D) Compiler error
(E) None of above


Explanation:
static variables are load time entity while auto variables are run time entity. We can not initialize any load time variable by the run time variable.
In this example i is run time variable while x is load time variable.
What is storage class?

19.

What will be output if you will compile and execute the following c code?

#define max 5;
void main(){
int i=0;
i=max++;
printf("%d",i++);
}

(A) 5
(B) 6
(C) 7
(D) 0
(E) Compiler error


Explanation:
#define is token pasting preprocessor. If you will see intermediate file: test.i
test.c 1:
test.c 2: void main(){
test.c 3: int i=0;
test.c 4: i=5++;
test.c 5: printf("%d",i++);
test.c 6: }
test.c 7:
It is clear macro constant max has replaced by 5. It is illegal to increment the constant number. Hence compiler will show Lvalue required.
Preprocessor questions and answer.

20.

What will be output if you will compile and execute the following c code?

void main(){
double far* p,q;
printf("%d",sizeof(p)+sizeof q);
}

(A) 12
(B) 8
(C) 4
(D) 1
(E) Compiler error


Explanation:

It is clear p is far pointer and size of far pointer is 4 byte while q is double variable and size of double variable is 8 byte.
Complete pointer tutorial.


If you need more explanation of above C multiple choice questions you are free to ask.


C programming language multiple choice questions and answers with explanation for interview

1.
What will be output if you will compile and execute the following c code?

void main(){
   int i=320;
   char *ptr=(char *)&i;
   printf("%d",*ptr);
}

(A) 320
(B) 1
(C) 64
(D) Compiler error
(E) None of above


Explanation:
As we know size of int data type is two byte while char pointer can pointer one byte at time.
Memory representation of int i=320

So char pointer ptr is pointing to only first byte as shown above figure.
*ptr i.e. content of first byte is 01000000 and its decimal value is 64.
Data type tutorial. 

2.

What will be output if you will compile and execute the following c code?

#define x 5+2
void main(){
    int i;
    i=x*x*x;
    printf("%d",i);
}

(A) 343
(B) 27
(C) 133
(D) Compiler error
(E) None of above


Explanation:
As we know #define is token pasting preprocessor it only paste the value of micro constant in the program before the actual compilation start. If you will see intermediate file you will find:
test.c 1:
test.c 2: void main(){
test.c 3: int i;
test.c 4: i=5+2*5+2*5+2;
test.c 5: printf("%d",i);
test.c 6: }
test.c 7:
You can absorb #define only pastes the 5+2 in place of x in program. So,
i=5+2*5+2*5+2
=5+10+10+2
=27
Preprocessor tutorial.

3.

What will be output if you will compile and execute the following c code?

void main(){
char c=125;
    c=c+10;
    printf("%d",c);
}

(A) 135
(B) +INF
(C) -121
(D) -8
(E) Compiler error


Explanation:
As we know char data type shows cyclic properties i.e. if you will increase or decrease the char variables beyond its maximum or minimum value respectively it will repeat same value according to following cyclic order:

So,
125+1= 126
125+2= 127
125+3=-128
125+4=-127
125+5=-126
125+6=-125
125+7=-124
125+8=-123
125+9=-122
125+10=-121

4.

What will be output if you will compile and execute the following c code?

void main(){
   float a=5.2;
  if(a==5.2)
     printf("Equal");
  else if(a<5.2)
     printf("Less than");
  else
     printf("Greater than");
}

(A) Equal
(B) Less than
(C) Greater than
(D) Compiler error
(E) None of above


Explanation:
5.2 is double constant in c. In c size of double data is 8 byte while a is float variable. Size of float variable is 4 byte.
So double constant 5.2 is stored in memory as:
101.00 11001100 11001100 11001100 11001100 11001100 11001101
Content of variable a will store in the memory as:
101.00110 01100110 01100110
It is clear variable a is less than double constant 5.2
Since 5.2 is recurring float number so it different for float and double. Number likes 4.5, 3.25, 5.0 will store same values in float and double data type.
Note: In memory float and double data is stored in completely different way. If you want to see actual memory representation goes to question number (60) and (61).
Data type tutorial.

5.

What will be output if you will compile and execute the following c code?

void main(){
  int i=4,x;
  x=++i + ++i + ++i;
  printf("%d",x);
}

(A) 21
(B) 18
(C) 12
(D) Compiler error
(E) None of above


Explanation:
In ++a, ++ is pre increment operator. In any mathematical expression pre increment operator first increment the variable up to break point then starts assigning the final value to all variable.
Step 1: Increment the variable I up to break point.

Step 2: Start assigning final value 7 to all variable i in the expression.


So, i=7+7+7=21
Operator tutorial.

6.

What will be output if you will compile and execute the following c code?

void main(){
 int a=2;
 if(a==2){
   a=~a+2<<1;
   printf("%d",a);
 }
 else{
  break;
 }
}

(A) It will print nothing.
(B) -3
(C) -2
(D) 1
(E) Compiler error


Explanation:
Keyword break is not part of if-else statement. Hence it will show compiler error: Misplaced break
Control statement tutorial

7.

What will be output if you will compile and execute the following c code?

void main(){
  int a=10;
  printf("%d %d %d",a,a++,++a);
}

(A) 12 11 11
(B) 12 10 10
(C) 11 11 12
(D) 10 10 12
(E) Compiler error


Explanation:
In c printf function follows cdecl parameter passing scheme. In this scheme parameter is passed from right to left direction.

So first ++a will pass and value of variable will be a=10 then a++ will pass now value variable will be a=10 and at the end a will pass and value of a will be a=12.
Function tutorial.

8.

What will be output if you will compile and execute the following c code?

void main(){
   char *str="Hello world";
   printf("%d",printf("%s",str));
}

(A) 11Hello world
(B) 10Hello world
(C) Hello world10
(D) Hello world11
(E) Compiler error


Explanation:
Return type of printf function is integer and value of this integer is exactly equal to number of character including white space printf function prints. So, printf(“Hello world”) will return 13.

9.

What will be output if you will compile and execute the following c code?

#include "stdio.h"
#include "string.h"
void main(){
   char *str=NULL;
   strcpy(str,"cquestionbank");
   printf("%s",str);
}

(A) cquestionbank
(B) cquestionbank\0
(C) (null)
(D) It will print nothing
(E) Compiler error


Explanation:
We cannot copy any thing using strcpy function to the character pointer pointing to NULL.
More questions of string.

10.

What will be output if you will compile and execute the following c code?

#include "stdio.h"
#include "string.h"
void main(){
  int i=0;
  for(;i<=2;)
   printf(" %d",++i);
}

(A) 0 1 2

(B) 0 1 2 3
(C) 1 2 3
(D) Compiler error
(E) Infinite loop


Explanation:
In for loop each part is optional.
Complete tutorial of looping in C.

11.

What will be output if you will compile and execute the following c code?

void main(){
  int x;
  for(x=1;x<=5;x++);
    printf("%d",x);
}

(A) 4
(B) 5
(C) 6
(D) Compiler error
(E) None of above


Explanation:
Body of for loop is optional. In this question for loop will execute until value of variable x became six and condition became false.
Looping tutorial.

12.

What will be output if you will compile and execute the following c code?

void main(){
printf("%d",sizeof(5.2));
}

(A) 2
(B) 4
(C) 8
(D) 10
(E) Compiler error


Explanation:
Default type of floating point constant is double. So 5.2 is double constant and its size is 8 byte.
Detail explanation of all types of constant in C.

13.

What will be output if you will compile and execute the following c code?

#include "stdio.h"
#include "string.h"
void main(){
char c='\08';
printf("%d",c);
}


(A) 8
(B) ’8’
(C) 9
(D) null
(E) Compiler error


Explanation:
In c any character is starting with character ‘\’ represents octal number in character. As we know octal digits are: 0, 1, 2, 3, 4, 5, 6, and 7. So 8 is not an octal digit. Hence ‘\08’ is invalid octal character constant.
Hexadecimal character constant.

14.

What will be output if you will compile and execute the following c code?

#define call(x,y) x##y
void main(){
int x=5,y=10,xy=20;
printf("%d",xy+call(x,y));
}

(A) 35
(B) 510
(C) 15
(D) 40
(E) None of above


Explanation:
## is concatenation c preprocessor operator. It only concatenates the operands i.e.
a##b=ab
If you will see intermediate file then you will find code has converted into following intermediate code before the start of actual compilation.
Intermediate file:
test.c 1:
test.c 2: void main(){
test.c 3: int x=5,y=10,xy=20;
test.c 4: printf("%d",xy+xy);
test.c 5: }
test.c 6:
It is clear call(x, y) has replaced by xy.
Preprocessor tutorial.

15.

What will be output if you will compile and execute the following c code?


int * call();
void main(){
int *ptr;
ptr=call();
clrscr();
printf("%d",*ptr);
}
int * call(){
int a=25;
a++;
return &a;
}


(A) 25
(B) 26
(C) Any address
(D) Garbage value
(E) Compiler error


Explanation:
In this question variable a is a local variable and its scope and visibility is within the function call. After returning the address of a by function call variable a became dead while pointer ptr is still pointing to address of variable a. This problem is known as dangling pointer problem.
Complete pointer tutorial.

16.

What is error in following declaration?

struct outer{
int a;
struct inner{
char c;
};
};

(A) Nesting of structure is not allowed in c.
(B)
It is necessary to initialize the member variable.
(C) Inner structure must have name.
(D) Outer structure must have name.
(E) There is not any error.


Explanation:
It is necessary to assign name of inner structure at the time of declaration other wise we cannot access the member of inner structure. So correct declaration is:
struct outer{
int a;
struct inner{
char c;
}name;
};
Union tutorial.

17.

What will be output if you will compile and execute the following c code?

void main(){
int array[]={10,20,30,40};
printf("%d",-2[array]);
}

(A) -60
(B) -30
(C) 60
(D) Garbage value
(E) Compiler error


Explanation:
In c,
array[2]=*(array+2)=*(2+array)=2[array]=30

18.

What will be output if you will compile and execute the following c code?

void main(){
int i=10;
static int x=i;
if(x==i)
printf("Equal");
else if(x>i)
printf("Greater than");
else
printf("Less than");
}

(A) Equal
(B) Greater than
(C) Less than
(D) Compiler error
(E) None of above


Explanation:
static variables are load time entity while auto variables are run time entity. We can not initialize any load time variable by the run time variable.
In this example i is run time variable while x is load time variable.
What is storage class?

19.

What will be output if you will compile and execute the following c code?

#define max 5;
void main(){
int i=0;
i=max++;
printf("%d",i++);
}

(A) 5
(B) 6
(C) 7
(D) 0
(E) Compiler error


Explanation:
#define is token pasting preprocessor. If you will see intermediate file: test.i
test.c 1:
test.c 2: void main(){
test.c 3: int i=0;
test.c 4: i=5++;
test.c 5: printf("%d",i++);
test.c 6: }
test.c 7:
It is clear macro constant max has replaced by 5. It is illegal to increment the constant number. Hence compiler will show Lvalue required.
Preprocessor questions and answer.

20.

What will be output if you will compile and execute the following c code?

void main(){
double far* p,q;
printf("%d",sizeof(p)+sizeof q);
}

(A) 12
(B) 8
(C) 4
(D) 1
(E) Compiler error


Explanation:

It is clear p is far pointer and size of far pointer is 4 byte while q is double variable and size of double variable is 8 byte.
Complete pointer tutorial.


If you need more explanation of above C multiple choice questions you are free to ask.

15 comments:

Anonymous said...

Really Its awesome.....

Cricket World Cup 2011 said...

Answer of Question number is=19
How? not 21 why ?

1m2r3a said...

19.

What will be output if you will compile and execute the following c code?

#define max 5;
void main(){
int i=0;
i=max++;
printf("%d",i++);
}

The correct answer is :
(E) Compiler error


Explanation:
file: test.i
test.c 1:
test.c 2: void main(){
test.c 3: int i=0;
test.c 4: i=5;++; //because u have define max as 5;
test.c 5: printf("%d",i++);
test.c 6: }
test.c 7:

C:\Users\Robert\Documents\c\test9\56789.c||In function 'main':|
C:\Users\Robert\Documents\c\test9\56789.c|4|error: expected expression before ';' token|

||=== Build finished: 1 errors, 0 warnings ===|

Anonymous said...

gud work....

Yasmin Mohamed said...

This code gives me compiler error
#define max 5;

void main(){
int i=0;
i=max++;
printf("%d",i++);
}

/////////////////////
The output of this code is 19 and I don't know why !!


void main(){
int i=4,x;
x=++i + ++i + ++i;
printf("%d",x);
}

Anonymous said...

NYC...questions...plzzz increases the no of questions

Rachit Parihar said...

Very nice questions,beautifully explained.
Thanks a lot brother.

Ravindra Chowdary Muppana said...

very nice questions...plzzz increases the no of questions

kushi chopra said...

whether we can use double quotes to include header files

sanjib badyakar said...

All questions. are very good but..less no of questions

CHETAN said...

yes kushi chopra you can include but there are two ways... just presentation is different

1) ==> system define .h(header file)

2) "myhead.h" ==> user define .h(header file)

Vishnu Thorat said...

its really nice c test skills............

VISHAL AGNIHOTRI said...

it depends upon compiler used..
for gcc its 21

for turbo its 19

SANTOSH KUMAR SHARMA said...

Great Website.

Ravina lashkari said...

its true