Programmer Plus 2007

home *** CD-ROM | disk | FTP | other *** search

/ Programmer Plus 2007 / Programmer-Plus-2007.iso / Programming / Low Level Languages / Assembly / KBD_IO.ASM < prev next >

Wrap

Assembly Source File | 1986-10-07 | 13.0 KB | 413 lines

CGROUP GROUP CODE_SEG, DATA_SEG ASSUME CS:CGROUP, DS:CGROUP ;-----------------------------------------------------------------------; ; This file contains procedures for working with the keyboard: ; ; ; ; READ_CHAR Read a character from the keyboard ; ; STRING_TO_UPPER Converts a string to upper case ; ; CHAR_TO_UPPER Converts a character to upper case ; ; READ_STRING Reads in a string of characters ; ; READ_DECIMAL Reads a decimal number ; ; READ_BYTE Reads a single byte ; ; HEX_TO_BYTE Converts to characters to a hex byte ; ; CONVERT_HEX_DIGIT Converts a hex digit to a nibble ; ;-----------------------------------------------------------------------; BS EQU 8 ;Back space character CR EQU 13 ;Carriage return character ESC EQU 27 ;Escape character DATA_SEG SEGMENT PUBLIC KEY_BOARD_INPUT LABEL BYTE CHAR_NUM_LIMIT DB 0 ;Length of input buffer NUM_CHARS_READ DB 0 ;Number of characters read CHARS DB 80 DUP (0) ;A buffer for keyboard input DATA_SEG ENDS CODE_SEG SEGMENT PUBLIC PUBLIC READ_CHAR ;-----------------------------------------------------------------------; ; This procedure reads a single character from the keyboard, without ; ; echoing it to the screen. ; ; ; ; Returns: AL Character, or 0 for special keys. ; ; AH Extended code of the special key ; ;-----------------------------------------------------------------------; READ_CHAR PROC NEAR MOV AH,7 ;Call for input with no checking INT 21h ;for CTRL_BREAK and no echo. OR AL,AL ;Is this a special key? JNZ DONE_READ_CHAR ;No, then we're all done INT 21h ;Yes, then read the extended code MOV AH,AL ;Save this in AH XOR AL,AL ;Signal that we have an extended code DONE_READ_CHAR: RET READ_CHAR ENDP PUBLIC STRING_TO_UPPER ;-----------------------------------------------------------------------; ; This procedure converts the string, using the DOS format for strings ; ; to all upper-case letters. ; ; ; ; DS:DX Address of string buffer. ; ; ; ; Uses: CHAR_TO_UPPER ; ;-----------------------------------------------------------------------; STRING_TO_UPPER PROC NEAR PUSH AX PUSH BX PUSH CX MOV BX,DX INC BX ;Point to character count MOV CL,[BX] ;Character count in 2nd byte of buffer XOR CH,CH ;Clear upper byte of count UPPER_LOOP: INC BX ;Point to next character in buffer MOV AL,[BX] ;Get one character from the string CALL CHAR_TO_UPPER ;Convert to upper-case letter MOV [BX],AL ;Save this character back to the string LOOP UPPER_LOOP POP CX POP BX POP AX RET STRING_TO_UPPER ENDP PUBLIC CHAR_TO_UPPER ;-----------------------------------------------------------------------; ; This procedure converts a single character to upper case. ; ; ; ; On entry: AL Character to convert ; ; Returns: AL Upper-case version of the letter ; ;-----------------------------------------------------------------------; CHAR_TO_UPPER PROC NEAR CMP AL,'a' ;Is this a lower-case letter? JB NOT_LOWER ;No, then we're all done CMP AL,'z' ;Is this a lower-case letter? JA NOT_LOWER ;No, then we're all done ADD AL,'A'-'a' ;Convert to upper-case letter NOT_LOWER: RET CHAR_TO_UPPER ENDP PUBLIC READ_STRING EXTRN WRITE_CHAR:NEAR ;-----------------------------------------------------------------------; ; This procedure performs a function very similar to the DOS 0AH ; ; function. But this function will return a special character if a ; ; function or key pad key is pressed -- no return for these keys. And ; ; ESC will erase the input and start over again. ; ; ; ; DS:DX Address for keyboard buffer. The first byte must ; ; contain the maximum number of characters to read (plus ; ; one for the return). And the second byte will be used ; ; by this procedure to return the number of characters ; ; actually read. ; ; 0 No characters read ; ; -1 One special character read ; ; otherwise number actually read (not including ; ; return key). ; ; ; ; Uses: READ_CHAR, BACK_SPACE, WRITE_CHAR ; ;-----------------------------------------------------------------------; READ_STRING PROC NEAR PUSH AX PUSH BX PUSH SI MOV SI,DX ;Use SI for index register and START_OVER: MOV BX,2 ;BX for offset to beginning of buffer CALL READ_CHAR OR AL,AL ;Is character extended ASCII? JZ EXTENDED ;Yes, then handle it. NOT_EXTENDED: ;Extnd char is error unless buff empty CMP AL,CR ;Is this a carriage return? JE END_INPUT ;Yes, we are done with input CMP AL,BS ;Is it a back space character? JNE NOT_BS ;Nope CALL BACK_SPACE ;Yes, delete character CMP BL,2 ;Is buffer empty? JE START_OVER ;Yes, can now read extended ASCII again JMP SHORT READ_NEXT_CHAR ;No, continue reading normal characters NOT_BS: CMP AL,ESC ;Is it an ESC -- purge buffer? JE PURGE_BUFFER ;Yes, then purge the buffer CMP BL,[SI] ;Check to see if buffer is full JA BUFFER_FULL ;Buffer is full MOV [SI+BX],AL ;Else save char in buffer INC BX ;Point to next free character in buffer PUSH DX MOV DL,AL ;Echo character to screen CALL WRITE_CHAR POP DX READ_NEXT_CHAR: CALL READ_CHAR OR AL,AL ;An extended ASCII char is not valid ;when the buffer is not empty. JNZ NOT_EXTENDED ;Char is valid ;Char is extended, signal error ;-----------------------------------------------; ; Signal an error condition by sending a beep ; ; character to the display: chr$(7). ; ;-----------------------------------------------; SIGNAL_ERROR: PUSH DX MOV DL,7 ;Sound the bell by writing chr$(7) MOV AH,2 INT 21H POP DX JMP SHORT READ_NEXT_CHAR ;Now read next character. ;-----------------------------------------------; ; Empty the string buffer and erase all the ; ; characters displayed on the screen. ; ;-----------------------------------------------; PURGE_BUFFER: PUSH CX MOV CL,[SI] ;Backspace over maximum number of XOR CH,CH PURGE_LOOP: ;characters in buffer. BACK_SPACE CALL BACK_SPACE ;will keep the cursor from moving too LOOP PURGE_LOOP ;far back. POP CX JMP START_OVER ;Can now read extended ASCII characters ;since the buffer is empty ;-----------------------------------------------; ; The buffer was full, so can't read another ; ; character. Send a beep to alert user of ; ; buffer full condition. ; ;-----------------------------------------------; BUFFER_FULL: JMP SHORT SIGNAL_ERROR ;If buffer full, just beep. ;-----------------------------------------------; ; Read the extended ASCII code and place this ; ; in the buffer as the only character, then ; ; return -1 as the number of characters read. ; ;-----------------------------------------------; EXTENDED: MOV [SI+2],AH ;Place extended code into the buffer MOV BL,0FFH ;Num chars read = -1 for special JMP SHORT END_STRING ;-----------------------------------------------; ; Save the count of the number of characters ; ; read and return. ; ;-----------------------------------------------; END_INPUT: ;Done with input. SUB BL,2 ;Count of characters read END_STRING: MOV [SI+1],BL ;Return number of chars read POP SI POP BX POP AX RET READ_STRING ENDP PUBLIC BACK_SPACE EXTRN WRITE_CHAR:NEAR ;-----------------------------------------------------------------------; ; This procedure deletes characters, one at a time, from the buffer and ; ; the screen when the buffer is not empty. BACK_SPACE simply returns ; ; when the buffer is empty. ; ; DS:SI+BX most recent character still in buffer. ; ; ; ; Uses: WRITE_CHAR ; ;-----------------------------------------------------------------------; BACK_SPACE PROC NEAR ;Delete one character PUSH AX PUSH DX CMP BX,2 ;Is buffer empty JE END_BS ;Yes, read the next character DEC BX ;remove one character from buffer MOV AH,2 ;Remove character from screen MOV DL,BS INT 21H MOV DL,20H ;Write space there CALL WRITE_CHAR MOV DL,BS ;Back-up again INT 21H END_BS: POP DX POP AX RET BACK_SPACE ENDP PUBLIC READ_DECIMAL ;-----------------------------------------------------------------------; ; This procedure takes the output buffer of READ_STRING and converts ; ; the string of decimal digits to a word. ; ; ; ; AX Word converted from decimal ; ; CF Set if error, clear if no error ; ; ; ; Uses: READ_STRING ; ; Reads: KEY_BOARD_INPUT, etc. ; ;-----------------------------------------------------------------------; READ_DECIMAL PROC NEAR PUSH BX PUSH CX PUSH DX MOV CHAR_NUM_LIMIT,6 ;Max number is 5 digits (65535) LEA DX,KEY_BOARD_INPUT CALL READ_STRING MOV CL,NUM_CHARS_READ ;Get number of characters read XOR CH,CH ;Set upper byte of count to zero CMP CL,0 ;Return error if no characters read JLE BAD_DECIMAL_DIGIT ;No chars read, signal error XOR AX,AX ;Start with number set to zero XOR BX,BX ;Start at beginning of string CONVERT_DIGIT: MOV DX,10 ;Multiply number by 10 MUL DX ;Multiply AX by 10 JC BAD_DECIMAL_DIGIT ;CF set if MUL overflowed one word MOV DL,CHARS[BX] ;Get the next digit SUB DL,'0' ;And convert to a nibble (4 bits) JS BAD_DECIMAL_DIGIT ;Bad digit if < 0. CMP DL,9 ;Is this a bad digit? JA BAD_DECIMAL_DIGIT ;Yes ADD AX,DX ;No, so add it to number INC BX ;Point to next character LOOP CONVERT_DIGIT ;Get the next digit DONE_DECIMAL: POP DX POP CX POP BX RET BAD_DECIMAL_DIGIT: STC ;Set carry to signal error JMP DONE_DECIMAL READ_DECIMAL ENDP PUBLIC READ_BYTE ;-----------------------------------------------------------------------; ; This procedure reads either a single ASCII character. This is just ; ; a test version of READ_BYTE. ; ; ; ; Returns byte in AL Character code (unless AH = 0) ; ; AH 1 if read ASCII char ; ; 0 if no characters read ; ; -1 if read a special key ; ; ; ; Uses: HEX_TO_BYTE, STRING_TO_UPPER, READ_STRING ; ; Reads: KEY_BOARD_INPUT, etc. ; ;-----------------------------------------------------------------------; READ_BYTE PROC NEAR PUSH DX MOV CHAR_NUM_LIMIT,3 ;Allow only two characters (plus enter) LEA DX,KEY_BOARD_INPUT CALL READ_STRING CMP NUM_CHARS_READ,1 ;See how many characters JE ASCII_INPUT ;Just one, treat as ASCII character JB NO_CHARACTERS ;Only enter key hit CMP NUM_CHARS_READ,0FFH ;Special function key? JE SPECIAL_KEY ;Yes. CALL STRING_TO_UPPER ;No, convert string to upper-case LEA DX,CHARS ;Address of string to convert CALL HEX_TO_BYTE ;Convert string from hex to byte JC NO_CHARACTERS ;Error, so return 'no characters read' MOV AH,1 ;Signal read one character DONE_READ: POP DX RET NO_CHARACTERS: XOR AH,AH ;Set to 'no characters read' JMP DONE_READ ASCII_INPUT: MOV AL,CHARS ;Load character read MOV AH,1 ;Signal read one character JMP DONE_READ SPECIAL_KEY: MOV AL,CHARS[0] ;Return the scan code MOV AH,0FFH ;Signal special key with -1 JMP DONE_READ READ_BYTE ENDP PUBLIC HEX_TO_BYTE ;-----------------------------------------------------------------------; ; This procedure converts the two characters at DS:DX from hex to one ; ; byte. ; ; ; ; DS:DX Address of two characters for hex number ; ;Returns: ; ; AL Byte ; ; CF Set for error, clear if no error ; ; AH changed ; ; ; ; Uses: CONVERT_HEX_DIGIT ; ;-----------------------------------------------------------------------; HEX_TO_BYTE PROC NEAR PUSH BX PUSH CX MOV BX,DX ;Put address in BX for indirect addr MOV AL,[BX] ;Get first digit CALL CONVERT_HEX_DIGIT JC BAD_HEX ;Bad hex digit if carry set MOV CX,4 ;Now multiply by 16 SHL AL,CL MOV AH,AL ;Retain a copy INC BX ;Get second digit MOV AL,[BX] CALL CONVERT_HEX_DIGIT JC BAD_HEX ;Bad hex digit if carry set OR AL,AH ;Combine two nibbles CLC ;Clear carry for no error DONE_HEX: POP CX POP BX RET BAD_HEX: STC ;Set carry for error JMP DONE_HEX HEX_TO_BYTE ENDP PUBLIC CONVERT_HEX_DIGIT ;-----------------------------------------------------------------------; ; This procedure converts a character from ASCII (hex) to a nibble (4 ; ; bits). ; ; ; ; AL character to convert ; ; Returns: AL nibble ; ; CF Set for error, cleared otherwise ; ;-----------------------------------------------------------------------; CONVERT_HEX_DIGIT PROC NEAR CMP AL,'0' ;Is it a legal digit? JB BAD_DIGIT ;Nope CMP AL,'9' ;Not sure yet JA TRY_HEX ;Might be hex digit SUB AL,'0' ;Is decimal digit, convert to nibble CLC ;Clear the carry, no error RET TRY_HEX: CMP AL,'A' ;Not sure yet JB BAD_DIGIT ;Not hex CMP AL,'F' ;Not sure yet JA BAD_DIGIT ;Not hex SUB AL,'A'-10 ;Is hex, convert to nibble CLC ;Clear the carry, no error RET BAD_DIGIT: STC ;Set the carry, error RET CONVERT_HEX_DIGIT ENDP CODE_SEG ENDS END