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Assembly Source File | 1987-10-02 | 32.4 KB | 742 lines

; Help.asm ; Resident help facility ; Format: HELP filespec [... filespec][/Nn][/P][/Hn] | [/U] ; defaults: pages = 4; hot key = Alt H CODE SEGMENT ;********************************; ASSUME CS:CODE,DS:CODE ;* *; ORG 100H ;* Requires MASM 2.0 or later *; ;* Remember to EXE2BIN *; START: JMP BEGINNING ;* *; ;********************************; ; DATA AREA ; --------- COPYRIGHT DB "HELP 1.0 (c) 1987 Ziff Communications Co.",13,10 DB "Successfully installed",13,10 ALT_COMBO DB "Press Alt H to activate",10,0,26 PROGRAMMER DB "Michael J. Mefford" OLD_KEYBOARD DD ? CRT_COLS DW ? STATUS_REG DW ? SCREEN_SEG DW 0B000H LINE_COUNT DB 25 IMMEDIATE_FLAG DB 0 BUSY DB 0 IMMEDIATE DW POP_IT DATA_SEG DW ? DATA_INT DB 0 INSTALLED_FLAG DB 0 POPUP_FLAG DB 0 HOT_KEY DB 35 FILENAME DW ? ERROR_LEVEL DB 0 CURRENT_PAGE DB 1 RESERVED_PAGES DB 4 ACTIVE_PAGES DB 0 PAGE_COUNT DB 0 DELIMITERS DB 9,32,13,44,";","/" SYNTAX LABEL BYTE DB 10,"Usage: HELP filespec [... filespec][/Nn][/Hn][/P] | [/U]",13,10,10 DB "/Nn where n = number of reserved pages (1-14); default = 4",13,10 DB "/Hn where n = Alt hot key combo (A-Z,0-9,",34,45,34,44,34,61,34 DB "); default = H",13,10 DB "/P = immediate pop-up",13,10 DB "/U = uninstall",13,10,10 DB "Use: PgUp PgDn Home End to navigate through HELP",13,10 DB 5 DUP(32),"ESC or hot key to exit",10,0 ACTIVE_MSG DB " active page(s)",13,10,0 RESERVED_MSG DB " total page(s)",13,10,10,0 UNLOAD_MSG DB 10,"HELP can't be uninstalled.",13,10 DB "Uninstall resident programs in reverse order.",10,0 UNINSTALL_MSG DB 10,"HELP uninstalled",10,0 NO_FREE DB "Too many resident programs",0 NOT_FOUND DB 32,"not found",13,10,0 NOT_ENOUGH DB "Not enough memory",0 ALLOCATE_MSG DB "Memory allocation error",13,10,0 SCAN_CODES LABEL BYTE DB 45,130,48,129,49,120,50,121,51,122,52,123,53,124 DB 54,125,55,126,56,127,57,128,61,131,65,30,66,48,67 DB 46,68,32,69,18,70,33,71,34,72,35,73,23,74,36,75,37 DB 76,38,77,50,78,49,79,24,80,25,81,16,82,19,83,31 DB 84,20,85,22,86,47,87,17,88,45,89,21,90,44 ; SCAN CODES FOR ALT COMBO ; ; Code Key Code Key Code Key Code Key ; 16 Q 30 A 44 Z 120 1 ; 17 W 31 S 45 X 121 2 ; 18 E 32 D 46 C 122 3 ; 19 R 33 F 47 V 123 4 ; 20 T 34 G 48 B 124 5 ; 21 Y 35 H 49 N 125 6 ; 22 U 36 J 50 M 126 7 ; 23 I 37 K 127 8 ; 24 O 38 L 128 9 ; 25 P 129 0 ; 130 - ; Default is 35 (Alt H) 131 = ;************* KEYBOARD INTERCEPTOR *************; NEW_KEYBOARD: STI PUSHF ;Simulate an interrupt CALL CS:OLD_KEYBOARD ; by pushing flags and far call. POP_IT: PUSHF ;On return save all registers PUSH DS ; that will be used. PUSH ES PUSH AX PUSH BX PUSH CX PUSH DX PUSH SI PUSH DI PUSH BP PUSH CS ;Point to our data. POP DS CLD ;Moves in forward direction. MOV AX,40H ;Point to ROM BIOS data area MOV ES,AX MOV AX,ES:[4AH] ;Get number of columns on screen MOV CRT_COLS,AX ; and store. MOV AX,ES:[63H] ;Get base address of video card. ADD AX,6 ;Convert to status register MOV STATUS_REG,AX ; and store. CMP AX,3BAH ;Is it mono card? JZ MONO ;If yes, use b800h. MOV SCREEN_SEG,0B800H ; else point to color card. MONO: MOV AL,ES:[49H] ;Retrieve video mode. CMP AL,3 ;Is it text mode? JBE GOOD_MODE ;If yes, OK. CMP AL,7 JNZ DONE_HERE ;Exit if graphics GOOD_MODE: CMP IMMEDIATE_FLAG,1 ;Is there a pop-up request? JZ NOW ;If yes, pop-up right now. CMP BUSY,1 ;If the window is already popped JZ DONE_HERE ; exit Int 9 back to window. MOV AH,1 ;Is an ASCII character ready? INT 16H JZ DONE_HERE ;If it's just a key release, exit. CMP AL,0 ;Is it extended code? JNZ DONE_HERE ;If no, exit. CMP AH,HOT_KEY ;Else, see if our Alt key combo. JZ OPEN_WINDOW ;If yes, open window DONE_HERE: JMP SHORT EXIT_KEYBOARD ; else exit. ;------------------------------------; ; Save screen so we can pop up HELP. ; ;------------------------------------; OPEN_WINDOW: MOV AH,0 ;Retrieve and discard hot key INT 16H ; character from keyboard buffer. NOW: MOV BUSY,1 ;Flag that window is open. MOV IMMEDIATE_FLAG,0 ;Restore immediate flag. CALL STORE_SCREEN ;Store screen. ;-----------------------------------------; ; Loop here looking for valid keystrokes. ; ;-----------------------------------------; READ_KEY: MOV CL,CURRENT_PAGE ;Get current page. DEC CL ;Adjust for starting offset. CALL PAGE_SIZE ;Get offset. MOV SI,DX CALL WRITE_SCREEN ;Update the screen. MOV AH,0 ;Wait for a character. INT 16H CMP AH,1 ;Is it Esc? JZ EXIT_WINDOW ;If yes, exit window. CMP AH,BYTE PTR HOT_KEY ;Is it our key combo? JZ EXIT_WINDOW ;If yes, exit window. MOV CL,CURRENT_PAGE ;Get current page. CMP AH,49H ;Is it PgUp? JNZ CK_PGDN CMP CL,1 ;If yes, is it already page one? JZ END_KEY DEC CL ;If no, decrement page. CK_PGDN: CMP AH,51H ;Is it PgDn? JNZ CK_HOME CMP CL,ACTIVE_PAGES ;If yes, are we already last page? JZ END_KEY INC CL ;If no, increment page. CK_HOME: CMP AH,47H ;Is it Home? JNZ CK_END MOV CL,1 ;If yes, move to page one. CK_END: CMP AH,4FH ;Is it End? JNZ END_KEY MOV CL,ACTIVE_PAGES ;If yes, move to last page. END_KEY: MOV CURRENT_PAGE,CL ;Store new current page. JMP SHORT READ_KEY ;----------------------------------; ; This is the window exit routine. ; ;----------------------------------; EXIT_WINDOW: MOV SI,OFFSET SCREEN_BUFFER ;Point to the stored screen CALL WRITE_SCREEN ; and restore the screen. MOV IMMEDIATE_FLAG,0 ;Reset the pop-up flag. MOV BUSY,0 ;Flag done with window. EXIT_KEYBOARD: POP BP ;Restore all registers. POP DI POP SI POP DX POP CX POP BX POP AX POP ES POP DS POPF IRET ;Return from interrupt. ;************* FILE LOADING AND INSTALL PROCEDURE *************; BEGINNING: CLD PUSH CS POP DATA_SEG ;Store our segment. CMP SP,65533 ;Do we have 64K? JA CK_PARA MOV SI,OFFSET NOT_ENOUGH ;If no, exit with message. JMP ERROR_EXIT CK_PARA: CMP BYTE PTR DS:[80H],0 ;Any parameters? JNZ CK_FREE OPTIONS: MOV SI,OFFSET SYNTAX ;If no, exit with syntax message. JMP ERROR_EXIT ;----------------------------------------------------------------------; ; Check user vectors to see if we are installed or if one is available ; ;----------------------------------------------------------------------; CK_FREE: MOV AL,60H - 1 ;Available vectors are 60H - 67H. FREE_USER_INT: INC AL MOV AH,35H ;Get vector address. INT 21H CMP BX,0 ;Is offset being used? JNZ CK_SIGNATURE ;If yes, see if it's us. MOV DX,ES CMP DX,0 ;Is segment being used? JNZ CK_SIGNATURE ;If yes, see if it's us. MOV DATA_INT,AL ;If available, save INT number. NEXT_USER: CMP AL,67H ;Have we checked all 7? JNZ FREE_USER_INT ;If no, next one. JMP SHORT CK_SWITCHES CK_SIGNATURE: MOV DI,BX ;See if INT has our signature. MOV SI,100H MOV CX,30/2 REPZ CMPSW JNZ NEXT_USER ;If yes, already installed. MOV DATA_SEG,ES ;Save segment. MOV INSTALLED_FLAG,1 ;--------------------------------------------; ; Check the command line for switch options. ; ;--------------------------------------------; CK_SWITCHES: PUSH DATA_SEG ;First point to installed segment. POP ES MOV SI,81H ;First parameter. NEXT_SWITCH: LODSB ;Get a byte. CMP AL,13 ;Is it carriage return? JZ CK_FILENAMES ;If yes, done here. CMP AL,"/" ;Is it switch character? JNZ NEXT_SWITCH ;If no, get next byte LODSB ; else get switch. CMP AL,13 ;Is it carriage return? JZ CK_FILENAMES ;If yes, done here CALL CAPITALIZE ; else capitalize. CMP AL,"U" ;Is it "U"? JNZ CK_N CMP INSTALLED_FLAG,1 ;If yes, are we installed? JNZ NEXT_SWITCH JMP UNINSTALL ;If yes, uninstall. CK_N: CMP AL,"N" ;Is it "N"? JNZ CK_P CMP INSTALLED_FLAG,1 ;If yes, are we installed? JZ NEXT_SWITCH ;If yes, can't change reserved. CALL DEC_TO_HEX ;Else, convert decimal to hex. CMP BL,14 ;Request greater than 14 pages JA NEXT_SWITCH ; or equal to zero? CMP BL,0 JZ NEXT_SWITCH ;If yes, ignore. MOV RESERVED_PAGES,BL ;Else, store reserved pages. JMP SHORT NEXT_SWITCH CK_P: CMP AL,"P" ;Is it "P"? JNZ CK_H MOV POPUP_FLAG,1 ;If yes, flag to pop-up immediate. CK_H: CMP AL,"H" ;Is it "H"? JNZ NEXT_SWITCH LODSB DEC SI ;Adjust in case it's just CR. CALL CAPITALIZE MOV DI,OFFSET SCAN_CODES MOV CX,38 ;38 possible Alt key combos. NEXT_ALT: SCASB ;Do we have a match? JZ GOT_ALT INC DI ;If no, bump pointer to next byte. LOOP NEXT_ALT JMP SHORT NEXT_SWITCH GOT_ALT: MOV ALT_COMBO + 10,AL ;Store Alt key. MOV AL,[DI] ;Get scan code MOV ES:HOT_KEY,AL ; and store. JMP SHORT NEXT_SWITCH ;-----------------------------------------------------; ; This routine parses the command line for filenames. ; ;-----------------------------------------------------; CK_FILENAMES: MOV SI,81H ;Point to first parameter. NEXT_FILENAME: CALL CK_DELIMITER ;Is it a delimiter? JC CK_CR ;If yes, see if end. MOV FILENAME,SI ;Else, store filename start. FIND_END: CALL CK_DELIMITER ;Look for delimiter to mark end. JNC FIND_END PUSH SI ;Save pointer and delimiter. PUSH AX CALL READ_FILE ;Read the file in. POP AX POP SI ;Restore pointers. CK_CR: CMP AL,13 ;Is it carriage return? JZ END_FILENAMES ;If yes, done here. CMP AL,"/" ;Is it switch character? JNZ NEXT_FILENAME ;If no, get next filename. FIND_SWITCH: CALL CK_DELIMITER ;Else, look for delimiter. JNC FIND_SWITCH JMP SHORT CK_CR ;And check if carriage return. END_FILENAMES: MOV AL,PAGE_COUNT ;Retrieve page count. CMP INSTALLED_FLAG,1 ;Are we installed? JZ STORE_ACTIVE ;If yes, check pages read. CMP AL,RESERVED_PAGES ;Pages read greater than reserved? JBE STORE_ACTIVE MOV RESERVED_PAGES,AL ;If yes, store as reserved. STORE_ACTIVE: CMP AL,0 ;Did we read any pages? JZ CK_INSTALLED1 ;If no, check if installed. MOV ES:ACTIVE_PAGES,AL ;Else, store active pages. MOV ES:CURRENT_PAGE,1 ;Reset the current page to one. JMP SHORT CK_POPUP ;Check popup request. CK_INSTALLED1: CMP INSTALLED_FLAG,1 ;Are we installed? JNZ CK_INSTALLED2 ;If no, exit. ;----------------------------------------; ; This routine does an immediate pop-up. ; ;----------------------------------------; CK_POPUP: CMP POPUP_FLAG,1 ;Is there a popup request? JNZ CK_INSTALLED2 ;If no, check pages read. MOV ES:IMMEDIATE_FLAG,1 ;Else, flag keyboard routine. PUSHF ;Simulate an interrupt. CALL DWORD PTR IMMEDIATE MOV BL,0 ;Error level of zero. CMP AL,0 ;Any pages read? JZ EXIT ;If no, done here. ;--------------------------------------------------; ; This routine checks to see if we are to install. ; ;--------------------------------------------------; CK_INSTALLED2: CMP AL,0 ;Did we fail to open a file? MOV SI,OFFSET SYNTAX ;If yes, exit with syntax message. JZ ERROR_EXIT PUSH AX MOV CL,AL ;Save active pages. MOV DL,10 CALL WRITE_IT ;Display linefeed. CALL WRITE_NUMBER ;Display active pages. MOV SI,OFFSET ACTIVE_MSG CALL DISPLAY_TEXT POP AX CMP INSTALLED_FLAG,1 ;Are we already installed? MOV BL,ERROR_LEVEL JZ EXIT ;If yes, done here CK_INT: CMP DATA_INT,0 ;Did we find a free user interrupt? JNZ INSTALL ;If yes, install MOV SI,OFFSET NO_FREE ;Else, exit with message. ;-------------------; ; This is the exit. ; ;-------------------; ERROR_EXIT: MOV BL,1 ;Error code of one. MSG_EXIT: CALL DISPLAY_TEXT EXIT: MOV AL,BL MOV AH,4CH ;Return with error code. INT 21H ;Terminate. ;--------------------------------; ; This is the install procedure. ; ;--------------------------------; INSTALL: MOV AX,DS:[2CH] ;Get environment segment. MOV ES,AX MOV AH,49H ;Free up environment. INT 21H MOV SI,OFFSET ALLOCATE_MSG JC ERROR_EXIT ;If error, exit with message. MOV DX,100H ;Install user interrupt as MOV AL,DATA_INT ; pointer to residency. MOV AH,25H INT 21H MOV AX,3509H ;Get keyboard interrupt. INT 21H MOV WORD PTR OLD_KEYBOARD,BX ;Save old interrupt. MOV WORD PTR OLD_KEYBOARD[2],ES MOV DX,OFFSET NEW_KEYBOARD ;Install new interrupt. MOV AX,2509H INT 21H MOV CL,RESERVED_PAGES ;Display reserved pages. CALL WRITE_NUMBER MOV SI,OFFSET RESERVED_MSG CALL DISPLAY_TEXT MOV SI,OFFSET COPYRIGHT ;Display install message. CALL DISPLAY_TEXT CALL PAGE_SIZE ;Convert reserved pages to offset. MOV CL,4 SHR DX,CL ;Convert to paragraphs. INC DX ;Round up one. MOV AX,3100H ;Return error code of zero. INT 21H ;Terminate but stay resident. ;*************; ; SUBROUTINES ; ;*************; ;-----------------------------------------------; ; This subroutine uninstalls the resident help. ; ;-----------------------------------------------; UNINSTALL: MOV AX,3509H ;Get keyboard interrupt. INT 21H CMP BX,OFFSET NEW_KEYBOARD ;Is the offset vector same? MOV SI,OFFSET UNLOAD_MSG ;Error message if INT 9h changed. MOV BL,1 ;Error code of one if fails. JNZ MSG_EXIT MOV AX,ES ;Is segment vector same? CMP AX,DATA_SEG JNZ MSG_EXIT ;If no, exit with error. MOV ES,DATA_SEG ;Point to resident segment. MOV AH,49H ;And return memory to system pool. INT 21H MOV SI,OFFSET ALLOCATE_MSG JNC DEALLOCATED ;Display message if problem. CALL DISPLAY_TEXT DEALLOCATED: MOV DX,ES:WORD PTR OLD_KEYBOARD ;Restore old INT 9. MOV DS,ES:WORD PTR OLD_KEYBOARD[2] MOV AX,2509H INT 21H MOV AL,ES:DATA_INT ;Retrieve user interrupt. XOR DX,DX MOV DS,DX ;Return vector to nulls. MOV AH,25H INT 21H PUSH CS POP DS MOV SI,OFFSET UNINSTALL_MSG ;Display uninstall message. MOV BL,0 ;Error code of zero. JMP MSG_EXIT ;And exit. ;-----------------------------------------; ; These subroutines display the messages. ; ;-----------------------------------------; WRITE_NUMBER: MOV BL,CL ;Retrieve number. CMP BL,10 ;Is it greater than ten? JB ONES MOV DL,"1" ;If yes, display a one. CALL WRITE_IT SUB BL,10 ONES: MOV DL,BL ADD DL,"0" ;Convert to decimal. CALL WRITE_IT ;Display one's digit. RET ;----------------------------------------; WRITE_IT: MOV AH,2 ;Display byte via DOS. INT 21H RET ;----------------------------------------; DISPLAY_IT: CALL WRITE_IT DISPLAY_TEXT: LODSB ;Get a byte MOV DL,AL CMP DL,0 ;Zero marks end of string. JNZ DISPLAY_IT RET ;-------------------------------------------------------------; ; This subroutine opens files if there is room to store them. ; ;-------------------------------------------------------------; READ_FILE: CALL CK_SPACE ;Is there room for help? JC END_READ MOV DX,FILENAME ;If yes, open file. DEC DX MOV AX,3D00H INT 21H JNC GOT_FILE MOV ERROR_LEVEL,1 ;Else, indicate had a problem. MOV SI,DX ;Display filename and message CALL DISPLAY_TEXT ; if file not found. MOV SI,OFFSET NOT_FOUND CALL DISPLAY_TEXT RET GOT_FILE: MOV BX,AX ;Filehandle in BX. NEXT_READ: CALL READ_IT ;Read it. JC CLOSE_FILE ;Done here if nothing read. CALL CK_SPACE ;If room, read balance, if any, JNC NEXT_READ ; into next page. CLOSE_FILE: MOV AH,3EH ;Close file. INT 21H END_READ: RET ;--------------------------------------------------------------------; ; This subroutine does the actual reading of help files into storage ; ;--------------------------------------------------------------------; READ_IT: MOV CL,PAGE_COUNT ;Retrieve page count. CALL PAGE_SIZE ;Convert to offset. PUSH ES POP DS ;Point to storage segment. MOV CX,4000 ;Read 4000 bytes. MOV AH,3FH INT 21H JC READ_END CMP AX,0 ;Did we read anything? JZ READ_END INC CS:PAGE_COUNT ;If yes, increment page count. SUB CX,AX ;Was it a full page? JZ SKIP_PAD MOV DI,DX ;If no, pad balance with nulls. ADD DI,AX XOR AL,AL REP STOSB SKIP_PAD: CLC ;Indicate read something. JMP SHORT RESTORE_DS READ_END: STC ;Indicate nothing read. RESTORE_DS: PUSH CS ;Restore data segment. POP DS RET ;------------------------------------------------; ; This subroutine checks for free storage space. ; ;------------------------------------------------; CK_SPACE: CMP PAGE_COUNT,14 ;Already a full 14 pages? JZ NO_SPACE ;If yes, no space. CMP INSTALLED_FLAG,1 ;Are we installed. JNZ SPACE MOV AL,ES:RESERVED_PAGES ;If yes, are reserved pages full? CMP AL,PAGE_COUNT JZ NO_SPACE ;If yes, no space. SPACE: CLC ;Else, there is space. RET NO_SPACE: STC RET ;-------------------------------------------------------; ; This subroutine calculates the page offsets. ; ; Enter with CL = multiplicand; Return with DX = offset ; ;-------------------------------------------------------; PAGE_SIZE: MOV AX,4000 ;Multiply by 4000 bytes. XOR DX,DX XOR CH,CH MUL CX MOV DX,OFFSET PAGE_BUFFER ;Add to page buffer offset. ADD DX,AX RET ;------------------------------------------; ; This subroutine converts decimal to hex. ; ;------------------------------------------; DEC_TO_HEX: XOR BL,BL ;Start with zero. NEXT_NUMBER: LODSB ;Get a byte. CMP AL,"0" ;Is it a number? JB END_NUMBER CMP AL,"9" JA END_NUMBER SUB AL,"0" ;If yes convert to hex. XCHG AL,BL ;Save it. XOR AH,AH ;Multiply previous by 10. MOV DL,10 MUL DL XCHG AL,BL ;Retrieve current number. ADD BL,AL ;And add to total. JMP SHORT NEXT_NUMBER END_NUMBER: DEC SI ;Adjust pointer. RET ;---------------------------------------------------------; ; This subroutine checks the command line for delimiters. ; ;---------------------------------------------------------; CK_DELIMITER: LODSB ;Get a byte. MOV DI,OFFSET DELIMITERS ;Point to delimiters. MOV CX,6 REPNZ SCASB ;And see if match. JNZ NO_DELIMITER MOV BYTE PTR [SI-1],0 ;If yes, convert to ASCIIZ. STC RET NO_DELIMITER: CLC RET ;-------------------------------------------------; ; This subroutine capitalizes the character in AL ; ;-------------------------------------------------; CAPITALIZE: CMP AL,"a" JB END_CAPS CMP AL,"z" JA END_CAPS AND AL,5FH END_CAPS: RET ;------------------------------------------------------------------; ; This subroutine stores the screen so it can be restored on exit. ; ;------------------------------------------------------------------; STORE_SCREEN: MOV LINE_COUNT,25 ;25 lines to save. MOV DX,STATUS_REG ;Retrieve status register. MOV AX,SCREEN_SEG ;Point to screen buffer. MOV DS,AX PUSH CS ;Point to storage segment. POP ES XOR SI,SI ;Top left corner. MOV DI,OFFSET SCREEN_BUFFER ;Point to storage offset. NEXT_LINE1: MOV BP,ES:CRT_COLS ;Retrieve screen columns. MOV CX,80 ;Save maximum of 80 columns. HORZ_RET1: IN AL,DX ;Get status. TEST AL,1 ;Is it low? JNZ HORZ_RET1 ;If no, wait until it is. CLI ;No more interrupts. WAIT1: IN AL,DX ;Get status TEST AL,1 ;Is it high? JZ WAIT1 ;If no, wait until it is. LODSW ;Retrieve a word. STI ;Interrupts back on. STOSW ;Store the character/attribute. DEC BP ;Decrement screen column count. JZ SHORT_COLS1 ;Was it less than 80? LOOP HORZ_RET1 ;If no, loop until row done. SHL BP,1 ;Convert balance to a word. ADD SI,BP ;Add to screen offset. JMP SHORT CK_LINES1 SHORT_COLS1: DEC CX ;Adjust balance. SHL CX,1 ;Convert to a word. ADD DI,CX ;Add to storage offset. CK_LINES1: DEC ES:LINE_COUNT ;Do all 25 lines. JNZ NEXT_LINE1 PUSH CS ;Restore data segment. POP DS RET ;Return. ;---------------------------------------------; ; This subroutine writes to the screen buffer ; ;---------------------------------------------; WRITE_SCREEN: MOV LINE_COUNT,25 ;25 lines to save. MOV DX,STATUS_REG ;Retrieve status register. MOV AX,SCREEN_SEG ;Point to screen buffer. MOV ES,AX XOR DI,DI ;Top left corner. NEXT_LINE2: MOV BP,CRT_COLS ;Retrieve screen columns. MOV CX,80 ;Write maximum of 80 columns. NEXT_BYTE: LODSW ;Get a byte. MOV BX,AX ;Store it in AX. HORZ_RET2: IN AL,DX ;Get status. TEST AL,1 ;Is it low? JNZ HORZ_RET2 ;If no, wait until it is. CLI ;No more interrupts. WAIT2: IN AL,DX ;Get status. TEST AL,1 ;Is it high? JZ WAIT2 ;If no, wait until it is. MOV AX,BX ;Retrieve the word STOSW ; and store it. STI ;Interrupts back on. DEC BP ;Decrement screen column count. JZ SHORT_COLS2 ;Was it less than 80? LOOP NEXT_BYTE ;If no, loop until row done. SHL BP,1 ;Convert balance to a word. ADD DI,BP ;Add to storage offset. JMP SHORT CK_LINES2 SHORT_COLS2: DEC CX ;Adjust balance. SHL CX,1 ;Convert to a word. ADD SI,CX ;Add to screen offset. CK_LINES2: DEC LINE_COUNT ;Do all 25 lines. JNZ NEXT_LINE2 RET SCREEN_BUFFER LABEL BYTE PAGE_BUFFER EQU SCREEN_BUFFER + ( 2 * 80 * 25 ) CODE ENDS END START