Q(uick)BASIC Function: INKEY$

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INKEY$

A device I/O function that reads a character from the keyboard

Worth knowing

Useful and cross-version information about the programming environments of QBasic and QuickBasic.

Syntax
  • INKEY$
Description/Parameter(s)
  • INKEY$ returns a null string if there is no character to return.
  • For standard keys, INKEY$ returns a 1-byte string containing the character read.
  • For extended keys, INKEY$ returns a 2-byte string made up of the null character (ASCII 0) and the keyboard scan code.
Example
PRINT "Press Esc to exit..." DO LOOP UNTIL INKEY$ = CHR$(27) '27 is the ASCII code for Esc.

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Syntax
  • INKEY$
Description/Parameter(s)

The INKEY$ function returns a one- or two-byte string containing a character read from the standard input device. A null string is returned if no character is waiting there. A one-character string contains the actual character read from the keyboard, while a two- character string indicates an extended code, the first character of which is hexadecimal 00.

See ⮜ Keyboard Scan Codes Table ⮞ and the ⮜ ASCII Character Codes Table ⮞ for a complete list of these codes.

The standard input device is usually the keyboard. INKEY$ does not echo characters to the screen; instead, all characters are passed through to the program except for the following:

CTRL+BREAK, which halts program execution
CTRL+ALT+DEL, which does a system reboot
CTRL+NUMLOCK, which causes program execution to pause
PRTSC, which prints the screen
Example

This example shows a common use of INKEY$. The program pauses until the user presses a key:

PRINT "Press any key to continue..." DO LOOP WHILE INKEY$=""

See also:

Syntax
  • INKEY$
Description/Parameter(s)

INKEY$ returns a 1- or 2-byte string that contains a character read from the standard input device, which usually is the keyboard:

  • A null string is returned if there is no character to return.
  • A one-character string contains the actual character read.
  • A two-character string indicates an extended ASCII code, the first character of which is hexadecimal 00.

See ⮜ Keyboard Scan Codes ⮞ and the ⮜ ASCII Character Codes ⮞ for a complete list of character codes that can be returned by the INKEY$ function.

Usage Notes

  • The character returned by the INKEY$ function is never displayed on the screen; instead, all characters are passed through to the program except for these key combinations:
Character Running under QBX Stand-alone .EXE File
Ctrl+Break Halts program execution. Halts program execution if compiled with the /D option; otherwise, passed through to program.
Ctrl+NumLock Pauses program execution until a key is pressed; then the next key pressed is passed through to the program. Same as running under QBX if compiled with /D option; otherwise, ignored (the program does not pause and no keystroke is passed).
Shift+PrtSc Prints the screen contents. Prints the screen contents.
Ctrl+Alt+Del Reboots the system. Reboots the system.
  • If you have assigned a string to a function key using the KEY statement and you press that function key when INKEY$ is waiting for a keystroke, INKEY$ will pass the string to the program. Enabled keystroke trapping takes precedence over the INKEY$ function.
  • When you use INKEY$ with ISAM programs, BASIC performs implicit CHECKPOINT operations to minimize data loss in the event of a power failure. The CHECKPOINT is performed if INKEY$ fails to successfully retrieve a character after 65,535 calls, and 20 seconds has expired. A CHECKPOINT writes open database buffers to disk.
Example

This example uses the INKEY$ function to cause a program to pause until a key is pressed.

PRINT "Press any key to continue..." DO LOOP WHILE INKEY$ = ""

See also: