; This file is an overlay to EDFILE.COM which provides modifications.
; Since EDFILE is a particularly popular public domain program and
; since more fixes and modifications are sure to follow, this patch
; will be referred to by its date...4 for 1984 and 09 for September.
; This patch by Clint Lew
; South Bay Technical Support Group RCP/M (213) 970-9238
; This patch corrects two small bugs in the current version.
; The first bug limited the size of the file to which direct jumps
; could be made. In the original version, for files greater than
; about 8000H, the "dump relative address" or "A" command would not
; consistently jump directly to all addresses. (Actually the address
; jump limit was dependent upon the file size).
; The second bug was a minor problem in that a jump to an address
; which happened to be on a sector boundary would send you to the
; block before the desired block.
ORG 0528H
PUSH H ;selected address
LHLD 27C3H ;address offset
CALL 2A3AH ;subtract offset from address
LXI D,7
CALL 29DCH ;divide by 128 to get record number
XCHG
LHLD 27BCH ;LOF record number
XCHG
MOV A,D
CMP H ;compare most significant byte
JC 0357H ;selected record greater than LOF
JNZ NEWREC ;less than LOF
MOV A,E
CMP L ;compare least significant byte
JZ 0357H ;selected record equals LOF
JC 0357H ;greater than LOF record
NEWREC: SHLD 27CAH ;store valid record number
JMP 0562H ;continue
END
;*************************************************************
; General usage instructions for using ASM overlays
;*************************************************************
; I N S T R U C T I O N S
;
;
; First, edit this file to your preferences using any editor.
; Wordstar in non-document mode works very well for this.
;
; Second, assemble this file using Digital Research's CP/M
; assembler ASM.COM. For the file ED409.ASM, enter ASM ED409.
;
; Lastly, use DDT to overlay the results of this EDOVR program
; onto EDFILE.COM. The procedure for this overlay follows:
;
; A>DDT EDFILE.COM
; DDT VERS 2.2
; NEXT PC
; 2C00 0100 (size varies with version)
; -IED409.HEX (note the "I" command)
; -R ("R" loads in the .HEX file)
; NEXT PC
; 2C80 0000
; -G0 (return to CP/M)
; A>SAVE 44 EDFILE.COM (now have a modified .COM file)
;
; = = = = = = = = = = = = = = = = = =
