C PROGRAMMING QUESTIONS AND ANSWER

C PROGRAMMING QUESTIONS AND ANSWER

(1) What will be output if you will compile and execute

the following c code?

#include<stdio.h>

struct marks{

int p:3;

int c:3;

int m:2;

};

int main(){

struct marks s={2,-6,5};

printf("%d %d %d",s.p,s.c,s.m);

return 0;

}

(a) 2 -6 5

(b) 2 -6 1

(c) 2 2 1

(d) Compiler error

(e) None of these

Answer: (c)
Explanation:

Binary value of 2: 00000010 (Select three two bit)

Binary value of 6: 00000110

Binary value of -6: 11111001+1=11111010

(Select last three bit)

Binary value of 5: 00000101 (Select last two bit)

(2) What will be output if you will compile and execute

the following c code?

#include<stdio.h>

int main(){

int huge*p=(int huge*)0XC0563331;

int huge*q=(int huge*)0xC2551341;

*p=200;

printf("%d",*q);

return 0;

}

(a)0

(b)Garbage value

(c)null

(d) 200

(e)Compiler error
Answer: (d)

Explanation:

Physical address of huge pointer p

Huge address: 0XC0563331

Offset address: 0x3331

Segment address: 0XC056
Physical address= Segment address * 0X10 + Offset

address

=0XC056 * 0X10 +0X3331

=0XC0560 + 0X3331

=0XC3891

Physical address of huge pointer q

Huge address: 0XC2551341

Offset address: 0x1341

Segment address: 0XC255

Physical address= Segment address * 0X10 + Offset

address

=0XC255 * 0X10 +0X1341

=0XC2550 + 0X1341

=0XC3891

Since both huge pointers p and q are pointing same

physical address so content of q will also same as

content of q.

(3) Write c program which display mouse pointer and

position of pointer. (In x coordinate, y coordinate)?

Answer:

#include<dos.h>

#include<stdio.h>

int main(){

union REGS i,o;

int x,y,k;
//show mouse pointer

i.x.ax=1;

int86(0x33,&i,&o);

while(!kbhit()) //its value will false when we hit

key in the key board

{
i.x.ax=3; //get mouse position

x=o.x.cx;

y=o.x.dx;

printf("(%d , %d)",x,y);

delay(250);

int86(0x33,&i,&o);

return 0;

(4) Write a c program to create dos command: dir.

Answer:

Step 1: Write following code.

#include <stdio.h>

#include <dos.h>

int main(int count,char *argv[]){

struct find_t q ;

int a;

if(count==1)

argv[1]="*.*";

a = _dos_findfirst(argv[1],1,&q);

if(a==0){

while (!a){

printf(" %s\n", q.name);
a = _dos_findnext(&q);

}

}

else{

}

return 0;

printf("File not found");
}

Step 2: Save the as list.c (You can give any name)

Step 3: Compile and execute the file.

Step 4: Write click on My computer of Window XP

operating system and select properties.

Step 5: Select Advanced -> Environment Variables

Step 6: You will find following window:

Click on new button (Button inside the red box)


Step 7: Write following:

Variable name: path

Variable value: c:\tc\bin\list.c (Path where you have saved)

Step 8: Open command prompt and write list and press enter.

(5) What will be output if you will compile and execute

the following c code?

#include<stdio.h>
 int main(){

int i;

float a=5.2;

char *ptr;

ptr=(char *)&a;

for(i=0;i<=3;i++)

return 0;

}

printf("%d ",*ptr++);
(a)0 0 0 0

(b)Garbage Garbage Garbage Garbage

(c)102 56 -80 32

(d)102 102 -90 64

(e)Compiler error

Answer: (d)

Explanation:

In c float data type is four byte data type while char

pointer ptr can point one byte of memory at a time.

Memory representation of float a=5.2

ptr pointer will point first fourth byte then third

byte then second byte then first byte.

Content of fourth byte:

Binary value=01100110

Decimal value= 64+32+4+2=102

Content of third byte:

Binary value=01100110

Decimal value=64+32+4+2=102

Content of second byte:
Binary value=10100110

Decimal value=-128+32+4+2=-90

Content of first byte:

Binary value=01000000

Decimal value=64

Note: Character pointer treats MSB bit of each byte

i.e. left most bit of above figure as sign bit.