System related function

1)      delay:- delay() is an inbuilt function that reside into dos.h and it is responsible to pause a continue execution for specified time. It accept an argument for time in millisecond.

Declaration Syntax:-

void delay(unsigned millisecond);

 

For example:-

                                         delay(2000);

2)      sleep:- sleep() is an inbuilt function that reside into header file dos.h and it is also responsible to pause a continue execution  for specified time. It accept an argument in second.

Declaration Syntax:-

void sleep(unsigned second);

                                       

For example:-

                                         sleep(2);

Example:-

void main()

{

clrscr();

printf(“Welcome to C”);

delay(2000);

printf(“\n Welcome to programming”);

sleep(2);

printf(“\n It is a demo”);

getch();

}

Output-------- Welcome to C

                          Welcome to programming

                          It is a demo

3)      kbhit():- kbhit() is an inbuilt function of conio.h and it is specially used for check keyboard stroke i.e any key press or not and it return an integer value as a following way:-

(i)                  It return 0(zero) until a key pressed.

(ii)                It returns -1 (minus one) when a key is pressed.

int kbhit();    Declaration Syntax:-

Syntax to call kbhit():- 

   

kbhit();

For example:-

void main()

{

clrscr();

while(1)

{

r=kbhit();

printf(“r=%d”,r);

sleep(1);

break;

}

getch();

}

Output--------      r=0              

                            r=0                 when not any key is pressed

                            r=0

                            r=0

                           r=-1               when key is pressed during execution

Example:-

Write a program in C to display a message i.e Welcome to C until user press any key and pause execution each time for 2 second.

void main()

{

clrscr();

while(!kbhit())

{

printf(“Welcome to C \n”);

sleep(2);

}

printf(“Execution Complete”);

getch();

}

Output-----------                        Welcome to C

                                                         Welcome to C

                                                         Welcome to C

                                                         ………………………

                                                         Execution Complete

                          OR

void main()

{      clrscr();

        textbackground(2);

while(!kbhit())

{        i=i+1;

         textcoor(i);

         cprintf(“\n \r Welcome to C”);

         sleep(2);                 }

printf(“Execution Complete”);

getch();

}