OSBGET

From BeebWiki
Jump to: navigation, search

Read (get) a byte

Contents

Specification

 6502   Z80   6809   PDP11   80x86   32016   ARM  On entry: On exit:
A A A R0 AL R1 R0 - = byte read
Y H Y R1 BX R2 R1 = handle preserved
Cy=EOF status

If the byte read is after the end of file, the carry flag is set on exit and the EOF-error-flag is set. After the EOF byte has been read, the next read produces an error. An error is generated if the object is a directory or doesn't have read access.

Calling from BBC BASIC

  • b%=BGET#ch calls OSBGET.

Special handles

Some systems allow BGET#0 to read from the character input stream via OSRDCH.

Entry points

  • BBC BASIC Entry Address: &FFD7
  • 6502 Entry Address: &FFD7, vectors via &0216
  • Z80 Entry Address: &FFD7, vectors via &FFD8
  • 6809 Entry Address: &FFD7, vectors via &FFD8
  • 80x86 Entry Address: INT &43, vectors via 0000:010C
  • 32000 Entry Address: SVC &0D
  • PDP-11 Entry Address: EMT 9, vector &09
  • ARM Entry Address: SWI &0A "OS_BGet", vector &0A

Implementations

All filing systems implement OSBGET.

Jgharston 16:56, 6 November 2009 (UTC)