name clear page 55,132 title 'CLEAR --- control PC display';; CLEAR Utility to clear display; and set character attributes;; Ray Duncan, Uncopyright (u) August 1983; This program may be freely copied,; mangled, enhanced, redistributed.;input equ 080h ;command line tail buffercr equ 0dh ;ASCII carriage return;cseg segment byte assume cs:cseg,ds:cseg; org 0100h ;since this will be ; a COM file;clear: ;initialize display... ;call BIOS video driver to mov ah,15 ;get current display mode: int 10h ;returns AL = mode, and ;AH = no. of columns. cmp al,7 ;if we are in graphics modes je clear0 ;(modes 4,5,6) then exit cmp al,3 ;but if we are in mode 0-3 ja clear9 ;or 7 then continue.clear0: ;set up size of window to ;be initialized... xor cx,cx ;set upper left corner of ;window to (X,Y)=(0,0) mov dh,24 ;set Y to 24 for lower right mov dl,ah ;corner, and X to the number dec dl ;of columns returned by BIOS ;minus 1 mov bh,7 ;initialize attribute byte ;to "normal" video display, ;i.e. white on black. ;set SI=address of command ;tail's length byte mov si,offset input cld ;clear the Direction Flag ;for "LODS" string instruction. lodsb ;check length byte to see if or al,al ;there's any command tail. jz clear8 ;no,go clear the screen ;with normal video attribute ;clear1: lodsb ;check the next byte of ;the command tail, cmp al,cr ;if carriage return je clear8 ;we are done. or al,20h ;fold the character to ;lower case. cmp al,'a' ;make sure it's in range a-z jb clear1 ;no, skip it cmp al,'z' ja clear1 ;no, skip it cmp al,'i' ;I=Set intensity jne clear2 ;jump if not I or bh,08 ;set intensity bit jmp short clear1clear2: cmp al,'r' ;R=Reverse jne clear3 ;jump if not R and bh,088h ;mask off old foreground/ ;background bits and or bh,070h ;change to reverse video jmp short clear1clear3: cmp al,'u' ;U=Underline jne clear4 ;jump if not U and bh,088h ;mask off old foreground/ ;background bits and or bh,01h ;change to underline jmp short clear1clear4: cmp al,'b' ;B=Blink jne clear5 ;jump if not B or bh,080h ;set blink bit jmp short clear1clear5: cmp al,'s' ;S=Silent jne clear1 ;if not S try next char. mov bh,0 ;if S command, rig for ;silent running. Clear ;the foreground/background ;display control fields, and ;don't bother to look for ;any more command characters. ;clear8: ;now we have decoded all ;the characters in the ;command tail, and are ready ;to initialize the display. ;BH= desired attribute ;CL,CH=(X,Y),upper left ; corner of window ;DL,DH=(X,Y),lower right ; corner of window mov ax,0600h ;AH = function type 6, ;AL = lines to scroll (zero) int 10h ;request initialization ;of window by BIOS ; mov ah,2 ;now set the cursor to mov bh,0 ;(X,Y)=(0,0), Page=0 xor dx,dx int 10h ;clear9: int 20h ;exit to PC-DOS;cseg ends; end clear
|
