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INKEY and INKEY$ are BASIC functions to:

  • wait a specified time for a character from the input stream
  • test for a keypress
  • return a value indicating the machine host/operating system type
Availability Present in all versions of BBC BASIC.
Syntax <numeric> = INKEY<numeric> <string> = INKEY$<numeric>
Token (hex) A6 (function) BF (function)
Description Reads an character from the input stream.


INKEY and INKEY$ call OSBYTE &81. INKEY returns a character or -1 for no character, INKEY$ returns a one-character string or a null string if nothing returned.

Wait for input character

   Argument: >=0
   Returns:  >=0, character returned
             -1, timed out
   Example:  key%=INKEY(200)
             REPEAT:k%=INKEY(10):PROCtick:UNTIL k%>-1
   Some systems allow a delay value with b15 set to return a 16-bit "deep"
   keyvalue distinguishing between special keys, such as function keys, and
   top-bit characters.[1][2]
   Example:  REPEAT:key%=INKEY(&80C8):UNTIL key%>-1
             IF key%=&190 THEN PRINT "Shift-f0 pressed"

Scan for a particular key

   Argument: -1..-128, negative key number
   Returns:  TRUE, key pressed
             FALSE, key not pressed

Scan for a range of keys

   Argument: -129...-255, lowest internal key number to start at EOR&7F
   Returns:  internal key number pressed, or 255 for none

Check machine type

Depending on what the program needs to know, OSBYTE &00 is usually the more appropriate call to make.

   Argument: -256
   Returns:  A value with the low byte indicating the host (I/O) machine type:
            &00 BBC A/B with OS 0.10
            &00 RM Nimus[3]
            &01 Acorn Electron OS
            &FF BBC Micro OS 1.00/1.20/1.23, Reuters OS R0.3 with *UK
            &FE BBC Micro (American OS A1.0), Reuters OS R0.3 with *US
            &FE NetBSD
            &FD Master 128 MOS 3.20/3.50
            &FC BBC Micro (West German MOS) - see note
            &FC Windows 32
            &FB BBC B+ 64/128 (OS 2.00)
            &FB Beos (Brandy Basic)
            &FA Acorn Business Computer OS 1.00/2.00
            &FA Cambridge Workstation OS 2.10
            &FA DOS with DJGPP extender (Brandy Basic)
            &F9 Communicator
            &F9 Linux
            &F8 MacOS X (Brandy Basic)
            &F7 Master ET MOS 4
            &F7 FreeBSD
            &F6 OpenBSD
            &F5 Master Compact MOS 5
            &F5 Amiga (Brandy Basic)
            &F4 Master 128 MOS 3.26
            &F4 GNU FreeBSD (Brandy Basic)
            &F3 GNU (Brandy Basic)
            &Ex Spectrum
                &E0 ZX Spectrum
                (INKEY-256 AND &F0)=&E0 gives TRUE for ZX Spectrum hardware
            &Dx Amstrad 464/664/6128, etc.
                (INKEY-256 AND &F0)=&D0 gives TRUE for Amstrad CPC hardware
            &Cx Commodore 64/64+/128, etc.
                (INKEY-256 AND &F0)=&C0 gives TRUE for Commodore hardware
            &Bx PDP11 Unix
                &B7 PDP11 Unix Version 7
                &B6 PDP11 Unix Version 6
                &B5 PDP11 Unix Version 5
                (INKEY-256 AND &F0)=&B0 gives TRUE for PDP11 hardware
            &Ax ARM-based systems
                &A0 Arthur 1.20
                &A1 RISC OS 2.00
                &A2 RISC OS 2.01
                &A3 RISC OS 3.0x
                &A4 RISC OS 3.1x
                &A5 RISC OS 3.50
                &A6 RISC OS 3.60
                &A7 RISC OS 3.7x
                &A8 RISC OS 4.0x
                &A9 RISC OS 4.3x
                &AA RISC OS 5.xx
                &AE RISC OS Pyromaniac
                &AF Springboard - an ARM-based development system plugged into
                  a PC)
                (INKEY-256 AND &F0)=&A0 gives TRUE for ARM hardware
            &8x Texas Instruments Calculator
                &83 TI-83+(SE)
                &84 TI-84+(SE)
                (INKEY-256 AND &F0)=&80 gives TRUE for TI Calculator
            &68 6809 system
            &63 6309 system
            &73 BBC BASIC on SDL abstraction from C source (ie ASC"s")
            &57 BBC BASIC for Windows (ie ASC"W")
            &53 BBC BASIC SDL abstraction from assembly language source
                (ie ASC"S")
                (INKEY-256 AND &DB)=&53 gives TRUE for R.T.Russell's
                BBC BASIC for Windows/SDL/etc
            &4D Matrix Brandy BASIC (ie ASC"M") for all builds from v1.22.6
                except RISC OS.
 The known examples of German BBC MOS return X=&FF.


The parameter to INKEY is a 16-bit number. The standard implementation interprets that as:

 <&8000   - wait for keypress
 &FF00+nn - scan for BBC keypress
 &FF00    - return host machine type

A parameter of &8000-&FEFF is undefined. Some systems extend INKEY as follows:

 &FE00+nn - scan for low level DOS/Window VK_xxxx keypress (cZ80Tube, console library)
 &FC00+nn - scan for low level SDL1.2 SDK_xxx keypress (Brandy test builds)
 &8000+nn - wait for keypress, return 16-bit character code (cZ80Tube, console library)

See Also


Jgharston 12:27, 28 May 2009 (UTC) Jgharston (talk) 17:25, 5 July 2018 (CEST)