August 2012 - C Program Examples

C Aptitude 24
C program is one of most popular programming language which is used for core level of coding across the board. C program is used for operating systems, embedded systems, system engineering, word processors,hard ware drivers, etc.

In this site, we have discussed various type of C programs till date and from now on, we will move further by looking at the C aptitude questions.

In the coming days, we will post C aptitude questions, answers and explanation for interview preparations.

The C aptitude questions and answers for those questions along with explanation for the interview related queries.

We hope that this questions and answers series on C program will help students and freshers who are looking for a job, and also programmers who are looking to update their aptitude on C program.
Some of the illustrated examples will be from the various companies, and IT industry experts.
Read more about C Programming Language . and read the C Programming Language (2nd Edition). by K and R.

Predict the output or error(s) for the following:

C aptitude 24.1

  main()
{
    printf("%x",-1<<4);
}

Answer: fff0

Explanation: -1 is internally represented as all 1’s. When left shifted four times the least significant 4 bits are filled with 0’s.The %x format specifier specifies that the integer value be printed as a hexadecimal value.

C aptitude 24.2

   main()
{
    char string[]="Hello World";
    display(string);
}
void display(char *string)
{
    printf("%s",string);
}

Answer: Compiler Error : Type mismatch in redeclaration of function display

Explanation:In third line, when the function display is encountered, the compiler doesn’t know anything about the function display. It assumes the arguments and return types to be integers, (which is the default type). When it sees the actual function display, the arguments and type contradicts with what it has assumed previously. Hence a compile time error occurs.

C aptitude 24.3

      main()
{
    int c=- -2;
    printf("c=%d",c);
}

Answer:c=2

Explanation: Here unary minus (or negation) operator is used twice. Same maths rules applies, ie. minus * minus= plus.
Note: However you cannot give like –2. Because — operator can only be applied to variables as a decrement operator (eg., i–). 2 is a constant and not a variable.

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#include<graphics.h>
#include<conio.h>
#include<dos.h>

void showmouseptr();
void hidemouseptr();

union REGS i, o;

int main()
{
int count = 1, gd = DETECT, gm;

initgraph(&gd,&gm,"C:\TC\BGI");/*check your path, to install the drivers in to the the system*/

i.x.ax = 0;
int86(0X33,&i,&o);
if(o.x.ax == 0)
{
printf("nt Sorry! Mouse support not available !");
}
else
{
showmouseptr();

while(count<=10)
{
getch();
count++;
if(count%2==0)
hidemouseptr();
else
showmouseptr();
}
}

getch();
return 0;
}

void showmouseptr()
{
i.x.ax = 1;
int86(0X33,&i,&o);
}

void hidemouseptr()
{
i.x.ax = 2; // to hide mouse
int86(0X33,&i,&o);
}

C Program Examples

Month: August 2012

C Aptitude Questions and answers with explanation

C program to hide the mouse pointers.