OSWRCH
Prints a character to the currently selected output stream(s).
Contents
Specification
6502 | Z80 | 6809 | PDP11 | 80x86 | 32016 | ARM | 68000 | RISC-V | On entry: | On exit: |
A | A | A | R0 | AL | R1 | R0 | D0 | A0 | = ASCII value of character to print | preserved |
Prints the character whose ASCII value is in A to the currently selected output stream(s), namely the screen, printer, serial port, spool file or any combination of these, or none. The character need not be in the ASCII repertoire of course; it may be part of a VDU sequence, a Teletext graphics character or a printer control code.
A complex process (see diagram, below) filters the characters according to
the *FX3
, *FX5
, *FX6
and
*SPOOL
settings, the flag returned by VDUCHR, and previous
characters submitted to OSWRCH. Each of the terminators (shown in blue) does
its own specific processing. The handling is 8 bit clean throughout.
OSBYTE commands affecting OSWRCH | |
OSBYTE &03 | Select output device |
OSBYTE &05 | Select printer type/output channel |
OSBYTE &06 | Select character to be ignored by printer |
VDU codes affecting flow of control | |
VDU 1 |
Send next character to printer only |
VDU 2 |
Enable printer |
VDU 3 |
Disable printer |
VDU 6 |
Enable VDU (screen) driver |
VDU 21 |
Disable VDU (screen) driver |
These five VDU commands are handled by VDUCHR. The other function of code 21, to erase the current line of input, is a feature of OSWORD 0.
Character output flowchart
Calling from BBC BASIC
-
LIST
sends output to OSWRCH -
LISTO
sends output to OSWRCH -
PRINT
sends output to OSWRCH -
VDU
sends output to OSWRCH -
CLS
sends VDU 12 -
CLG
sends VDU 16 -
COLOUR n
sends VDU 17,n -
GCOL a,n
sends VDU 18,a,n -
GCOL n
sends VDU 18,0,n -
COLOUR l,p
sends VDU 19,l,p,0,0,0 -
COLOUR l,r,g,b
sends VDU 19,l,16,r,g,b if l>=0 -
COLOUR l,r,g,b
sends VDU 19,l,24,r,g,b if l<0 -
MODE n
sends VDU 22,n -
OFF
sends VDU 23,1,0,0,0,0,0,0,0,0 -
ON
sends VDU 23,1,1,0,0,0,0,0,0,0 -
PLOT k,x,y
sends VDU 25,k,x;y; -
PLOT BY x,y
sends PLOT 65,x,y -
PLOT x,y
sends PLOT 69,x,y -
MOVE BY x,y
sends PLOT 0,x,y -
DRAW BY x,y
sends PLOT 1,x,y -
MOVE x,y
sends PLOT 4,x,y -
DRAW x,y
sends PLOT 5,x,y -
CIRCLE x,y,r
sends MOVE x,y:PLOT 145,r,0 -
CIRCLE FILL x,y,r
sends MOVE x,y:PLOT 153,r,0 -
ELLIPSE x,y,a,b
sends MOVE x,y:MOVE BY a,0:PLOT 193,0,b -
ELLIPSE FILL
sends MOVE x,y:MOVE BY a,0:PLOT 201,0,b -
FILL x,y
sends PLOT 133,x,y -
FILL BY x,y
sends PLOT 129,x,y -
LINE x1,y1,x2,y2
sends MOVE x1,y1:DRAW x2,y2 -
RECTANGLE x,y,w
sends MOVE x,y:PLOT 13,x+w,y:PLOT 13,x+w,y+w:PLOT x,y+w:PLOT 13,x,y -
RECTANGLE x,y,w,h
sends MOVE x,y:PLOT 13,x+w,y:PLOT 13,x+w,y+h:PLOT x,y+h:PLOT 13,x,y -
RECTANGLE FILL x,y,w
sends MOVE x,y:PLOT 101,x+w,y+w -
RECTANGLE FILL x,y,w,h
sends MOVE x,y:PLOT 101,x+w,y+h -
RECTANGLE x1,y1,w,h TO x2,y2
sends MOVE x1,y1:MOVE x1+w,y1+h:PLOT 190,x2,y2 -
RECTANGLE FILL x1,y1,w,h TO x2,y2
sends MOVE x1,y1:MOVE x1+w,y1+h:PLOT 189,x2,y2 -
RECTANGLE SWAP x1,y1,w,h TO x2,y2
sends MOVE x1,y1:MOVE x1+w,y1+h:PLOT 191,x2,y2 -
ORIGIN x,y
sends VDU 29,x;y; -
PRINT TAB(x,y);
sends VDU 31,x,y
Entry points
- BBC BASIC Entry Address: &FFEE
- 6502 Entry Address: &FFEE, vectors via &020E
- Z80 Entry Address: &FFEE, vectors via &FFEF
- 6809 Entry Address: &FFEE, vectors via &FFEF
- 80x86 Entry Address: INT &49, vectors via 0000:0124
- 32000 Entry Address: SVC &01
- PDP11 Entry Address: EMT 4, vector &04
- ARM Entry Address: SWI &00 "OS_WriteC", vector &03
- 68000 Entry Address: MOV #&00,A0:TRAP 12
- RISC-V Entry Address: ECALL &AC0004
Implementations
Implemented in all MOS versions. Some systems allow BPUT#0
to
send output to OSWRCH. The flags are usually corrupted on exit. On 6502
systems the Z flag reflects the contents of A due to the routine ending with
a PLA to restore A.
Jgharston 17:03, 6 November 2009 (UTC)