OSBYTE &00

OSBYTE &00 (0): Identify Host/Operating System

On entry, X=0  - Generate error number 247 giving host and OS type
          X<>0 - Return host/OS in X

On exit,  X=host/OS type:
  0 Electron/Communicator  8 UNIX-type system                         24 CP/M-type system
  1 BBC                    9 6809/6309 system     17 6809/6309 system
  2 BBC B+                10 Apple/Mac/etc
  3 Master 128
  4 Master ET                                                         28 Commodore 64/128
  5 Master Compact                                                    29 Texas Instruments calculator
  6 Arthur or RISC OS                                                 30 Amstrad CPC
  7 Springboard                                                       31 Sinclair ZX Spectrum
 Filesystem used:
    :d.dir.file/ext          dir/file.ext            :d.dir.file/ext     d:file.ext

On exit,  X=host/OS type:
 32 (&20) IBM PC-type system (DOS, Windows, etc.)
 43 (&2B) DEC DOS11/RSX11/RSTS/RT11 (DOS-style filesystem)
 57 (&39) 6809/6309 system with DOS-style filesystem
 Filesystem used:
    d:\dir\file.ext

Implementations

Early documentation refers to OSBYTE 0 as returning the OS version. As more systems were developed, it became more correct to refer to it returning a value indicating the host. For example, code running on a second processor will always be told what the I/O host is regardless of what the host is and what the second processor is.

80x86 BBC BASIC running on DOS and Windows returns 32 as a side effect of reading the character under the cursor. Properly written code that calls OSBYTE 0 will know to do so in a manner that ensures this occurs. Normally this just means calling OSBYTE 0 at program startup before outputting anything.

When writing a host, OSBYTE 0,0 should generate an error with the text in the form:

• "MOS NAME a.bc"
• or "MOS NAME a.bc (dd Mmm yyyy)"
• or "MOS NAME a.bc (dd Mmm yyyy) additional info"

Platform capabilities

Over time the OSBYTE 0 return value has evolved to become a bitmap representing the capabilities of the host system, primarily of the file system structure.

• %000x0xxx Filenames are directory.filename/extension, eg BBC, RISC OS
• %000x1xxx Filenames are directory/filename.extension, eg Unix, CP/M
• %nnnxxxxx Filenames are directory\filename.extension, eg DOS, Windows

This can also be represented as:

• %000x0xxx Directory seperator is '.'
• %000x1xxx Directory seperator is '/'
• %nnnxxxxx Directory seperator is '\'

• %000x0xxx Extension seperator is '/'
• %nnnxnxxx Extension seperator is '.'

This allow programs to use code similar to the following:

  A%=0:X%=1:os%=((USR&FFF4)AND&FF00)DIV256
  d$=".":s$="/":IF(os%AND-24):d$="/":s$=".":IF(os%AND-32):d$="\"
  filename$=dir$+d$+name$+s$+ext$

See also

• Multiplatform programming

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Jgharston 22:41, 6 September 2007 (BST) Jgharston (talk) 06:35, 12 April 2020 (CEST)