INKEY$ function

INKEY$ returns a string of 0, 1, or 2 characters that reflects the status of the keyboard buffer. It can also return a string of four bytes if mouse event trapping is enabled. INKEY$ will always read keys from the keyboard, regardless of STDIN redirection status.

A null string (LEN(i$) = 0) means that the buffer is empty (no key or mouse event is available).

A string length of one (LEN(i$) = 1) means that an ASCII key was pressed and the string contains the ASCII character. Values between 1 and 31 indicate a control code.

A string length of two (LEN(i$) = 2) means that an extended key was pressed. In this case, the first character in the string has a value of zero, and the second is the extended keyboard code. For example, pressing the F1 key will return CHR$(0,59).

A string length of four (LEN(i$) = 4) means that a mouse event was retrieved. In this case, the first two characters in the string have a value of 255. The third character is an event code:

*Value*	Definition
1	movement
2	double-click
4	button press
8	button release

*Value*	Definition
0	no button
1	left
2	right
4	second left button
8	third left button
16	fourth left button

For example, moving the mouse with the left button pressed will return CHR$(255, 255, 1, 1). Button presses can be combined, for example pressing the left and right mouse buttons together will return CHR$(255, 255, 4, 3). The Mouse must be enabled with the MOUSE statement in order to receive mouse events.

If you are converting DOS code to PB/CC, you are likely to come across the following type of loop:

While both of these loops work fine in PB/CC, they take as much CPU attention as possible. As a result, this type of loop is very wasteful and can cause other applications to work sluggishly, even when the PB/CC app is running in the background. The solution is to add a SLEEP 0 statement within the loop (to release the current CPU time-slice to other tasks) or, better, use the WAITKEY$ function instead.