C questions and answers

C questions and answers with explanation

1. Data types        2. Operators              3. Pointers
4. Arrays            5. Loops                  5. Preprocessor
6. Structures        6. If else                6. Switch case
7. printf            8. Variables              7. File handling
8. Strings           9. Command line arguments

C questions and answers for interview

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1. Practice set 1    2. Practice set_2         3. Practice set_3

C tutorials:

1. Memory mapping    2. Variables              3. Data types
4. Storage Class     5. Looping                5. Pointers
6. Functions         6. Arrays                 6. Preprocessor
7. File handling     8. Advance c    
         
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C interview questions and answers


C interview questions and answers for freshers. It is basic c language technical frequently asked interview questions and answers. It includes data structures, pointers interview questions and answers for experienced
Interview questions and answer of C with explanation for fresher

1
Write a c program to print Hello world without using any semicolon.
Answer
Explanation:
Solution: 1
void main(){
    if(printf("Hello world")){
    }
}

Solution: 2
void main(){
    while(!printf("Hello world")){
    }
}

Solution: 3
void main(){
    switch(printf("Hello world")){
    }
}

2
Swap two variables without using third variable.
Answer
Explanation:
#include<stdio.h>
int main(){
    int a=5,b=10;
//process one
    a=b+a;
    b=a-b;
    a=a-b;
    printf("a= %d  b=  %d",a,b);

//process two
    a=5;
    b=10;
    a=a+b-(b=a);
    printf("\na= %d  b=  %d",a,b);
//process three
    a=5;
    b=10;
    a=a^b;
    b=a^b;
    a=b^a;
    printf("\na= %d  b=  %d",a,b);
   
//process four
    a=5;
    b=10;
    a=b-~a-1;
    b=a+~b+1;
    a=a+~b+1;
    printf("\na= %d  b=  %d",a,b);
   
//process five
    a=5,
    b=10;
    a=b+a,b=a-b,a=a-b;
    printf("\na= %d  b=  %d",a,b);
    return 0;
}

3
What is dangling pointer in c? 
Answer
Explanation:
Dangling pointer:

If any pointer is pointing the memory address of any variable but after some variable has deleted from that memory location while pointer is still pointing such memory location. Such pointer is known as dangling pointer and this problem is known as dangling pointer problem.

Initially:

Later:
For example:

What will be output of following c program?

#include<stdio.h>

int *call();
int main(){

int *ptr;
ptr=call();

fflush(stdin);
printf("%d",*ptr);
return 0;
}
int * call(){

int x=25;
++x;

return &x;
}

Output: Garbage value
Note: In some compiler you may get warning message returning address of local variable or temporary

Explanation: variable x is local variable. Its scope and lifetime is within the function call hence after returning address of x variable x became dead and pointer is still pointing ptr is still pointing to that location.

Solution of this problem: 
Make the variable x is as static variable. In other word we can say a pointer whose pointing object has been deleted is called dangling pointer.

#include<stdio.h>

int *call();
int main(){
int *ptr;
ptr=call();

fflush(stdin);
printf("%d",*ptr);
return 0;
}
int * call(){

static int x=25;
++x;

return &x;
}

Output: 26

4
What is wild pointer in c?  
Answer
Explanation:
A pointer in c which has not been initialized is known as wild pointer.

Example:

What will be output of following c program?

int main(){
int *ptr;
printf("%u\n",ptr);
printf("%d",*ptr);
return 0;
}

Output: Any address
Garbage value

Here ptr is wild pointer because it has not been initialized. There is difference between the NULL pointer and wild pointer. Null pointer points the base address of segment while wild pointer doesn’t point any specific memory location.

5