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Fix possible AX clobbering in writechar

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Cesar Blum 2020-09-27 20:37:43 -07:00
parent a34ab7f802
commit a280069ec4
1 changed files with 3 additions and 1 deletions
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4
sectorforth.asm
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@ -419,9 +419,11 @@ token:
; a line, but does not move it back to the previous line. ; a line, but does not move it back to the previous line.
; writechar addresses that. ; writechar addresses that.
writechar: writechar:
push ax ; INT 10h/AH=03h clobbers AX in some BIOSes
mov bh,0 ; video page 0 for all BIOS calls mov bh,0 ; video page 0 for all BIOS calls
mov ah,3 ; get cursor position (DH=row, DL=column) mov ah,3 ; get cursor position (DH=row, DL=column)
int 0x10 int 0x10
pop ax ; restore AX
mov ah,0x0e ; teletype output mov ah,0x0e ; teletype output
mov bl,0x7 ; black background, light grey text mov bl,0x7 ; black background, light grey text
int 0x10 int 0x10
@ -435,7 +437,7 @@ writechar:
int 0x10 int 0x10
.1: ret .1: ret
times 510-($-$$) db 0 ;times 510-($-$$) db 0
db 0x55, 0xaa db 0x55, 0xaa
; New dictionary entries will be written starting here. ; New dictionary entries will be written starting here.