The character returned by this function when the zero flag is clear is not removed from the type-ahead buffer. The same character and scan code will be returned by the next call to Int 16H Function 00H.Determines whether a character is ready for input, returning a flag and also the character itself, if one is waiting.
Call with:
AH = 01H
Returns:
If key waiting to be input
Zero flag = clear
AH = keyboard scan code
AL = character
If no key waiting
Zero flag = set
Note:
The character returned by this function when the zero flag is clear is not removed from the type-ahead buffer. The same character and scan code will be returned by the next call to Int 16H Function 00H.