delay

Syntax

#include <dos.h> void delay(unsigned msec);

Description

This function causes the program to pause for msec milliseconds. It uses the int 15h delay function to relinquish the CPU to other programs that might need it.

Some operating systems that emulate DOS, such as OS/2, Windows/NT, Windows 2000 and Windows XP hang the DOS session when the Pause key is pressed during the call to delay. Plain DOS and Windows 3.X and 9X are known to not have this bug. On Windows 2000 and XP to exit the pause press any key.

Some operating systems, such as Windows 2000 and XP which do not support int 15h. int 1ah is used instead on these operating systems. This method has lower accuracy in the delay length.

Windows 2000 and XP delay resolution is 54.9 millisecond. Under Windows 2000 and XP the delay function uses the Time Of Day Tick which occurs 18.2 times per second. This limits the accuracy of the delay to around 27 milliseconds on Windows 2000 and XP. On Windows 2000 and XP the Programable Interval Timer works and is a source of higher resolution than delay currently uses. Unfortunately PIT and Time Of Day tic does not appear to be coordinated.

Return Value

None.

Portability

ANSI/ISO C	No
POSIX	No

Example

delay(200); /* delay for 1/5 second */