title 'BDOS patch for CP/M 2.2 to make USER 0 public'
;
;5/15/80
;
;patch courtesy of Andy Johnson-Laird
;
;******************************CAUTION******************************
;
;This patch is for grown-ups who know what they are doing.
;Note that if files of the same name are present on both USER 0 and
;the logged-in USER number, the OPEN, SEARCH for FIRST, SEARCH for NEXT
;and READ SEQUENTIAL functions will match directory entries on a first-come
;first-served basis. This will cause exciting results if multiple extent
;files of the same name are present on both USER 0 and logged-in USER.
;
;Recommended use:
;
; 1) Keep on USER 0 only commonly used programs (Files.COM)
; 2) Set these programs to $SYS to reduce directory clutter.
; 3) Set these programs to $R/O to avoid accidental erasure of
; invisible programs.
; 4) NEVER place on any other USER number programs of the same name.
; 5) Have turn-key applications cold-boot directly into the assigned
; USER number. The USER number is the high nibble of address 4.
;
;
msize equ 20 ;set your memory size here
;
bdos equ (msize-20)*1024+3C00h
;
patch$area equ ?????? ;this will depend on YOUR system, and
;should probably be in your BIOS area
;
org bdos+075eh
jmp patch ;overlays: mov a,b
; cpi 0dh
;
;
org patch$area
patch: mov a,b
ora a
jnz patch2
ldax d
cpi 0e5h
jz patch2
mov a,m
ora a
jz bdos+077ch
patch2: mov a,b
cpi 0dh
jmp bdos+0761h
;
end
