OSBYTE &81

OSBYTE &81 (129) - Read Key with Time Limit or Machine Type. Called by BASIC's =INKEY function.

   Action: Read key with time limit
    On entry: X=0..255
              Y=0..127
    On exit:  Cy=0 character read, Y=0, X=character read
              Cy=1, Y=255 timed out
              Cy=1, Y=27  ESCAPE was pressed
    The caller can test for either Y=0 or Cy=0 for a valid returned character.

   Action: Read OS version
    On entry: X=0
              Y=255
    On exit:  X=value identifying the host OS
              X=&00 BBC A/B with OS 0.10
              X=&00 RM Nimus
              X=&01 Acorn Electron OS
              X=&FF BBC Micro OS 1.00/1.20/1.23, Reuters OS R0.3 with *UK
              X=&FE BBC Micro (American OS A1.0), Reuters OS R0.3 with *US
              X=&FE NetBSD
              X=&FD Master 128 MOS 3.20/3.50
              X=&FC BBC Micro (West German MOS) - see note
              X=&FC Windows 32
              X=&FB BBC B+ 64/128 (OS 2.00)
              X=&FB Beos (Brandy Basic)
              X=&FA Acorn Business Computer OS 1.00/2.00
              X=&FA Cambridge Workstation OS 2.10
              X=&FA DOS with DJGPP extender (Brandy Basic)
              X=&F9 Linux
              X=&F8 MacOS X (Brandy Basic)
              X=&F7 Master ET MOS 4
              X=&F7 FreeBSD
              X=&F6 OpenBSD
              X=&F5 Master Compact MOS 5
              X=&F5 Amiga (Brandy Basic)
              X=&F4 Master 128 MOS 3.26
              X=&F4 GNU FreeBSD (Brandy Basic)
              X=&F3 GNU (Brandy Basic)
              X=&Ex Spectrum
              X=&Dx Amstrad 464/664/6128, etc.
              X=&Cx Commodore 64/64+/128, etc.
              X=&Bx PDP11 Unix
              X=&B7 PDP11 Unix Version 7
              X=&B6 PDP11 Unix Version 6
              X=&Ax ARM-based systems
              X=&A0 Arthur 1.20
              X=&A1 RISC OS 2.00
              X=&A2 RISC OS 2.01
              X=&A3 RISC OS 3.0x
              X=&A4 RISC OS 3.1x
              X=&A5 RISC OS 3.50
              X=&A6 RISC OS 3.60
              X=&A7 RISC OS 3.7x
              X=&A8 RISC OS 4.0x
              X=&A9 RISC OS 4.3x
              X=&AA RISC OS 5.xx
              X=&AF Springboard   (An ARM-based development system plugged into a PC)
              X=&8x TI Calculator
              X=&68 6809 system
              X=&63 6309 system
              X=&73 BBC BASIC for ARM CPU on SDL abstraction (ie ASC"s")
              X=&57 BBC BASIC for Windows (ie ASC"W")
              X=&53 BBC BASIC for Intel CPU on SDL abstraction (ie ASC"S")
   
   The known examples of German BBC MOS return X=&FF.

   Action: Scan for a range of keys
    On entry: X=1..127 lowest internal key number to start at EOR &7F
              Y=255
    On exit:  X=internal key number pressed (or 255 for none)

   Action: Scan for a particular key
    On entry: X=128..255 internal key number to scan for EOR &80
              Y=255
    On exit:  X=Y=0 for as not pressed
              X=Y=255 the key was being pressed

Extensions

The parameter to OSBYTE &81 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 Basic SDL builds)
 &8000+nn - wait for keypress, return 16-bit character code (cZ80Tube, console library)

See Also

• http://mdfs.net/Docs/Comp/BBC/Osbyte80
• http://mdfs.net/Docs/Comp/Acorn/HostVals
• http://mdfs.net/Docs/Comp/Acorn/Hosts
• What BASIC is running
• Negative INKEY numbers

See Also

• http://mdfs.net/Docs/Comp/BBC/Osbyte80

Jgharston 21:56, 26 May 2009 (UTC) Jgharston (talk) 05:20, 23 June 2018 (CEST) Jgharston (talk) 22:09, 25 August 2019 (CEST)