mirror of
https://github.com/vxunderground/MalwareSourceCode.git
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100 lines
4.8 KiB
NASM
100 lines
4.8 KiB
NASM
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;DROPSY TEXT effect for Nowhere Man's VCL - TASM will assemble as is using
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;VCL recommended switches. When screen is thoroughly dropsie'd, that is all
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;letters have fallen to a single line across the bottom of the monitor,
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;the routine will exit to DOS and restore the command prompt. I excerpted
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;quite a bit of this from some public domain video routines optimized for
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;the accursed a86 assembler and reworked the whole magilla until TASM
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;wouldn't choke when swallowing the source. It attempts to meet
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;minimum requirements for VCL formatting. Heck, this is a nice routine
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;to have at your fingertips; you gotta admit a CASCADE-virus-like effect
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;is always something people wanna see. And it's commented up the
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;kazoo, one of the features I like best about VCL code. Hope you find
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;it useful. -URNST KOUCH
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code segment byte public
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assume cs:code,ds:code,es:code,ss:code
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org 0100h
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jmp Start
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main proc near
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Row dw 24 ;Rows to do initially
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;First, get current video mode and page.
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Start: mov cx,0B800h ;color display, color video mem for page 1
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mov ah,15 ;Get current video mode
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int 10h
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cmp al,2 ;Color?
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je A2 ;Yes
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cmp al,3 ;Color?
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je A2 ;Yes
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cmp al,7 ;Mono?
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je A1 ;Yes
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int 20h ;No,quit
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;here if 80 col text mode; put video segment in ds.
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A1: mov cx,0A300h ;Set for mono; mono videomem for page 1
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A2: mov bl,0 ;bx=page offset
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add cx,bx ;Video segment
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mov ds,cx ;in ds
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;start dropsy effect
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xor bx,bx ;Start at top left corner
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A3: push bx ;Save row start on stack
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mov bp,80 ;Reset column counter
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;Do next column in a row.
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A4: mov si,bx ;Set row top in si
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mov ax,[si] ;Get char & attr from screen
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cmp al,20h ;Is it a blank?
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je A7 ;Yes, skip it
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mov dx,ax ;No, save it in dx
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mov al,20h ;Make it a space
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mov [si],ax ;and put on screen
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add si,160 ;Set for next row
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mov di,cs:Row ;Get rows remaining
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A5: mov ax,[si] ;Get the char & attr from screen
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mov [si],dx ;Put top row char & attr there
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A6: call Vert ;Wait for 2 vert retraces
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mov [si],ax ;Put original char & attr back
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;Do next row, this column.
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add si,160 ;Next row
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dec di ;Done all rows remaining?
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jne A5 ;No, do next one
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mov [si-160],dx ;Put char & attr on line 25 as junk
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;Do next column on this row.
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A7: add bx,2 ;Next column, same row
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dec bp ;Dec column counter; done?
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jne A4 ;No, do this column
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;Do next row.
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A8: pop bx ;Get current row start
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add bx,160 ;Next row
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dec cs:Row ;All rows done?
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jne A3 ;No
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A9: mov ax,4C00h
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int 21h ;Yes, quit to DOS with error code
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;routine to deal with snow on CGA screen.
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Vert: push ax
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push dx
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push cx ;Save all registers used
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mov cl,2 ;Wait for 2 vert retraces
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mov dx,3DAh ;CRT status port
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F1: in al,dx ;Read status
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test al,8 ;Vert retrace went hi?
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je F1 ;No, wait for it
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dec cl ;2nd one?
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je F3 ;Yes, write during blanking time
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F2: in al,dx ;No, get status
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test al,8 ;Vert retrace went low?
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jne F2 ;No, wait for it
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jmp F1 ;Yes, wait for next hi
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F3: pop cx
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pop dx
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pop ax ;Restore registers
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ret ;and return
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main endp
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code ends
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end main
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