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https://github.com/vxunderground/MalwareSourceCode
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441 lines
13 KiB
NASM
441 lines
13 KiB
NASM
; DDIR.ASM -- Double Column Sorted DIR Command
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; ========
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; (C) Copyright Charles Petzold, 1985
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;
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; COM file format
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;
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CSEG Segment
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Assume CS:CSEG, DS:CSEG
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Org 002Ch ; Offset of Environment
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Environment Label Byte
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Org 007Bh ; Parameter for COMMAND.COM
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NewParameter Label Byte
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Org 0080h ; Parameter passed to program
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OldParameter Label Byte
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Org 0100h ; Entry point
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Entry: Jmp Begin
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; All Data
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; --------
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db '(C) Copyright Charles Petzold, 1985'
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DosVersMsg db "Needs DOS 2.0 +$" ; Error messages
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MemAllocMsg db "Memory Problem$"
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CommandMsg db "COMMAND Problem$"
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Comspec db "COMSPEC=" ; Search string in environment
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CommandAsciiz dd ? ; Eventual pointer to COMMAND
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ParamBlock dw ? ; Parameter Block for EXEC
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dw NewParameter,? ; First ? must be replaced
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dw 5Ch,? ; with Environment segment;
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dw 6Ch,? ; others with this segment
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OldInterrupt21 dd ? ; For vector address storage
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BufferPtr dw Offset FileBuffer ; For storing files listing
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CharCounter dw 0 ; Keeps track of characters
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NowDoingFile db 0 ; Flagged for file printed
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WithinFileList db 0 ; Flagged for file list
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FileCounter dw 0 ; Keeps track of files
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LineCounter db 0 ; For pausing at screen end
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PauseMessage db 6 dup (205)," Press any key to continue "
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db 6 dup (205),181
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PauseMsgEnd Label Byte
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; Check DOS Version
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; -----------------
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Begin: Mov AH,30h ; DOS Version function call
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Int 21h ; Call DOS
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Cmp AL,2 ; Check if version 2
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Jae DosVersOK ; If equal or over, all OK
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Mov DX,Offset DosVersMsg ; Wrong DOS version message
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ErrorExit: Mov AH,9 ; Set up for string write
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Int 21h ; Call DOS for message
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Int 20h ; Dishonorable discharge
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; Adjust stack and un-allocate rest of memory
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; -------------------------------------------
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DosVersOK: Mov DI,Offset FileBuffer ; Place to save files
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Mov CX,528 * 39 ; Allow room for 528 files
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Mov AL,' ' ; Will clear with blanks
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Cld ; Forward direction
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Rep Stosb ; Clear the area
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Mov BX,(Offset FileBuffer) + (528 * 39) + 100h
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; New end of program
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Mov SP,BX ; Set the stack pointer
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Add BX,15 ; Add 15 for rounding
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Mov CL,4 ; Number of shifts
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Shr BX,CL ; Convert AX to segment
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Mov AH,4Ah ; DOS call to shrink down
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Int 21h ; allocated memory
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Mov DX,Offset MemAllocMsg ; Possible error message
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Jc ErrorExit ; Only print it if Carry set
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; Search for Comspec in Environment
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; ---------------------------------
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Mov ES,[Environment] ; Environment Segment
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Sub DI,DI ; Start search at beginning
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Cld ; String increment to forward
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TryThis: Cmp Byte Ptr ES:[DI],0 ; See if end of environment
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Jz NoFindComSpec ; If so, we have failed
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Push DI ; Save environment pointer
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Mov SI,Offset ComSpec ; String to search for
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Mov CX,8 ; Characters in search string
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Repz Cmpsb ; Check if strings are same
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Pop DI ; Get back the pointer
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Jz FoundComspec ; Found string only zero flag
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Sub AL,AL ; Zero out AL
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Mov CX,8000h ; Set for big search
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Repnz Scasb ; Find the next zero in string
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Jmp TryThis ; And do the search from there
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NoFindComSpec: Mov DX,Offset CommandMsg ; Message for COMSPEC error
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Jmp ErrorExit ; Print it and exit
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FoundComspec: Add DI,8 ; So points after 'COMSPEC='
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Mov Word Ptr [CommandASCIIZ],DI ; Save the address of
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Mov Word Ptr [CommandASCIIZ + 2],ES ; COMMAND ASCIIZ
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; Set up parameter block for EXEC call
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; ------------------------------------
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Mov [ParamBlock],ES ; Segment of Environment string
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Mov [ParamBlock + 4],CS ; Segment of this program
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Mov [ParamBlock + 8],CS ; so points to FCB's
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Mov [ParamBlock + 12],CS ; and NewParameter
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; Save and set Interrupt 21h vector address
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; -----------------------------------------
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Mov AX,3521h ; DOS call to get Interrupt 21
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Int 21h ; vector address
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Mov Word Ptr [OldInterrupt21],BX ; Save offset
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Mov Word Ptr [OldInterrupt21 + 2],ES ; And segment
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Mov DX,Offset NewInterrupt21; Address of new Interrupt 21
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Mov AX,2521h ; Do DOS call to
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Int 21h ; set the new address
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; Fix up new parameter for "/C DIR" String
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; ------------------------------------
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Mov AL,[OldParameter] ; Number of parameter chars
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Add AL,5 ; We'll be adding five more
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Mov [NewParameter],AL ; Save it
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Mov Word Ptr [NewParameter + 1],'C/' ; i.e. "/C"
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Mov Word Ptr [NewParameter + 3],'ID' ; Then "DI"
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Mov Byte Ptr [NewParameter + 5],'R' ; And "R"
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; Load COMMAND.COM
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; -----------------
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Push CS ; Push this segment so we can
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Pop ES ; set ES to it
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Mov BX,Offset ParamBlock ; ES:BX = address of block
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Lds DX,[CommandAsciiz] ; DS:DX = address of ASCIIZ
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Mov AX,4B00h ; EXEC call 4Bh, type 0
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Int 21h ; Load command processor
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; Return from COMMAND.COM
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; -----------------------
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Mov AX,CS ; Get this segment in AX
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Mov DS,AX ; Set DS to it
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Mov SS,AX ; And SS for stack segment
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Mov SP,(Offset FileBuffer) + (528 * 39) + 100h
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; Set Stack again
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PushF ; Save Carry for error check
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Push DS ; Save DS during next call
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Mov DX,Word Ptr [OldInterrupt21] ; Old Int 21 offset
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Mov DS,Word Ptr [OldInterrupt21 + 2]; and segment
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Mov AX,2521h ; Call DOS to set vector
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Int 21h ; address to original
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Pop DS ; Restore DS to this segment
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PopF ; Get back Carry flage
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Jnc NormalEnd ; Continue if no error
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Mov DX,Offset CommandMsg ; Otherwise we'll print error
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Jmp ErrorExit ; message and exit
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NormalEnd: Int 20h ; Terminate program
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; New Interrupt 21h
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; -----------------
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NewInterrupt21 Proc Far
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Sti ; Allow further interrupts
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Cmp AH,40h ; Check if file / device write
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Je CheckHandle ; If so, continue checks
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SkipIntercept: Jmp CS:[OldInterrupt21] ; Just jump to old interrupt
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CheckHandle: Cmp BX,1 ; Check if standard output
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Jne SkipIntercept ; Not interested if not
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PushF ; Push all registers that
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Push AX ; we'll be messing with
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Push CX
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Push SI
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Push DI
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Push ES
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Push CS ; Push the code segment
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Pop ES ; So we can set ES to it
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Cld ; Forward for string transfers
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Mov SI,DX ; Now DS:SI = text source
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Mov DI,CS:[BufferPtr] ; And ES:DI = text destination
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Cmp CX,2 ; See if two chars to write
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Jne RegularChars ; If not, can't be CR/LF
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Cmp Word Ptr DS:[SI],0A0Dh ; See if CR/LF being written
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Jne RegularChars ; Skip rest if not CR/LF
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Mov CX,CS:[CharCounter] ; Get characters in line
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Mov CS:[CharCounter],0 ; Start at new line
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Cmp CS:[NowDoingFile],1 ; See if CR/LF terminates file
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Jnz AllowTransfer ; If not, just write to screen
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Mov AX,39 ; Max characters per line
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Sub AX,CX ; Subtract those passed
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Add CS:[BufferPtr],AX ; Kick up pointer by that
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Mov CS:[NowDoingFile],0 ; Finished with file
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Jmp PopAndReturn ; So just return to COMMAND
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RegularChars: Add CS:[CharCounter],CX ; Kick up counter by number
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Cmp CS:[CharCounter],CX ; See if beginning of line
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Jne NotLineBegin ; If not, must be in middle
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Cmp Byte Ptr DS:[SI],' ' ; See if first char is blank
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Jne ItsAFile ; If not, it's a file line
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Cmp CS:[WithinFileList],1 ; See if doing file listing
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Jne AllowTransfer ; If not, just print stuff
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Call SortAndList ; Files done -- sort and list
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Mov CS:[WithinFileList],0 ; Not doing files now
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Jmp Short AllowTransfer ; So just print the stuff
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ItsAFile: Cmp CS:[FileCounter],528 ; See if 11 buffer filled up
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Jb NotTooManyFiles ; If not just continue
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Push CX ; Otherwise, save this register
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Call SortAndList ; Print all up to now
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Mov CS:[FileCounter],0 ; Reset the counter
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Mov DI,Offset FileBuffer ; And the pointer
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Mov CS:[BufferPtr],DI ; Save the pointer
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Mov CX,528 * 39 ; Will clear for 528 files
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Mov AL,' ' ; With a blank
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Rep Stosb ; Clear it out
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Pop CX ; And get back register
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NotTooManyFiles:Mov CS:[WithinFileList],1 ; We're doing files now
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Mov CS:[NowDoingFile],1 ; And a file in particular
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Inc CS:[FileCounter] ; So kick up this counter
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NotLineBegin: Cmp CS:[NowDoingFile],1 ; See if doing files
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Je StoreCharacters ; If so, store the stuff
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AllowTransfer: Pop ES ; Pop all the registers
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Pop DI
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Pop SI
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Pop CX
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Pop AX
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PopF
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Jmp SkipIntercept ; And go to DOS for print
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StoreCharacters:Mov DI,CS:[BufferPtr] ; Set destination
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Rep Movsb ; Move characters to buffer
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Mov CS:[BufferPtr],DI ; And save new pointer
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PopAndReturn: Pop ES ; Pop all the registers
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Pop DI
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Pop SI
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Pop CX
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Pop AX
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PopF
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Mov AX,CX ; Set for COMMAND.COM
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Clc ; No error here
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Ret 2 ; Return with CY flag cleared
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NewInterrupt21 EndP
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; Sort Files
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; ----------
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SortAndList: Push BX ; Push a bunch of registers
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Push DX
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Push SI
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Push DS
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Push CS ; Push CS
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Pop DS ; so we can set DS to it
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Assume DS:CSEG ; And inform the assembler
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Mov DI,Offset FileBuffer ; This is the beginning
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Mov CX,[FileCounter] ; Number of files to sort
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Dec CX ; Loop needs one less than that
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Jcxz AllSorted ; But zero means only one file
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SortLoop1: Push CX ; Save the file counter
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Mov SI,DI ; Set source to destination
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SortLoop2: Add SI,39 ; Set source to next file
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Push CX ; Save the counter,
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Push SI ; compare source,
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Push DI ; and compare destination
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Mov CX,39 ; 39 characters to compare
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Repz Cmpsb ; Do the compare
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Jae NoSwitch ; Jump if already in order
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Pop DI ; Get back these registers
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Pop SI
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Push SI ; And push them again for move
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Push DI
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Mov CX,39 ; 39 characters
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SwitchLoop: Mov AL,ES:[DI] ; Character from destination
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Movsb ; Source to destination
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Mov DS:[SI - 1],AL ; Character to source
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Loop SwitchLoop ; For the rest of the line
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NoSwitch: Pop DI ; Get back the registers
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Pop SI
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Pop CX
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Loop SortLoop2 ; And loop for next file
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Pop CX ; Get back file counter
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Add DI,39 ; Compare with next file
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Loop SortLoop1 ; And loop again
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; Now Display Sorted Files
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; ------------------------
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AllSorted: Mov SI,Offset FileBuffer ; This is the beginning
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Mov CX,[FileCounter] ; Number of files to list
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Inc CX ; In case CX is odd
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Shr CX,1 ; CX now is number of lines
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SetIncrement: Mov BX,24 * 39 ; Increment for double list
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Cmp CX,24 ; But use it only if a full
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Jae LineLoop ; screen is printed
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Mov AX,39 ; Otherwise find increment
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Mul CX ; by multiplying CX by 39
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Mov BX,AX ; And make that the increment
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LineLoop: Call PrintFile ; Print the first column file
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Mov AL,' ' ; Skip one space
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Call PrintChar ; by printing blank
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Mov AL,179 ; Put a line down the middle
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Call PrintChar
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Mov AL,' ' ; Skip another space
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Call PrintChar
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Add SI,BX ; Bump up source by increment
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Sub SI,39 ; But kick down by 39
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Call PrintFile ; Print the second column file
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Call CRLF ; And terminate line
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Sub SI,BX ; Bring pointer back down
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Inc [LineCounter] ; One more line completed
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Cmp [LineCounter],24 ; Have we done whole screen?
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Jz PauseAtEnd ; If so, gotta pause now
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Loop LineLoop ; Otherwise just loop
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Jmp Short AllFinished ; And jump out when done
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PauseAtEnd: Mov [LineCounter],0 ; Reset the counter
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Add SI,BX ; Go to next file
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Push BX ; Save these registers
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Push CX
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Mov DX,Offset PauseMessage ; Test to print
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Mov CX,Offset PauseMsgEnd - Offset PauseMessage
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; Number of characters
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Mov BX,2 ; Standard ERROR Output
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Mov AH,40h ; Display to screen
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Int 21h ; By calling DOS
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Pop CX ; Retrieve pushed registers
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Pop BX
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Mov AH,8 ; Wait for character
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Int 21h ; Through DOS call
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Call CRLF ; Go to next line
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Loop SetIncrement ; And recalculate increment
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AllFinished: Pop DS ; Done with subroutine
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Pop SI
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Pop DX
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Pop BX
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Ret ; So return to caller
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; Display Routines
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; ----------------
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PrintChar: Mov DL,AL ; Print character in AL
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Mov AH,2 ; By simple DOS call
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Int 21h
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Ret ; And return
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CRLF: Mov AL,13 ; Print a carriage return
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Call PrintChar
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Mov AL,10 ; And a line feed
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Call PrintChar
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Ret ; And return
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PrintString: Lodsb ; Get character from SI
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Call PrintChar ; Print it
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Loop PrintString ; Do that CX times
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Ret ; And return
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PrintFile: Push CX ; Save the counter
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Mov CX,32 ; Bytes for Name, Size, & Date
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Call PrintString ; Print it
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Inc SI ; Skip one space before time
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Mov CX,6 ; Bytes for Time
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Call PrintString ; It's a print!
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Pop CX
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Ret ; And return
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FileBuffer Label Byte ; Points to end of code
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CSEG EndS ; End of segment
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End Entry ; Denotes entry point
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