;Program 4-2 performs the following,  (1) clears the screen,  (2) sets the cursor at the beginning of the third line   ;from the top of the screen,  (3) accepts the message "IBM perSonal COmputer" from the keyboard,  
;(4) converts lowercase letters of the message to uppercase, (5) displays the converted results on the next line.


TITLE        PROG4-2
PAGE         60,132
             .MODEL SMALL
             .STACK 64
;--------------
        .DATA
BUFFER  DB              22,?,22 DUP (?)         ;BUFFER FOR KEYED-IN DATA
        ORG     18H
DATAREA DB      CR,LF,22 DUP (?),'$'    ;AREA TO PLACE DATA AFTER CONVERSION
;
CR      EQU       0DH
LF      EQU       0AH
;------------
        .CODE
MAIN    PROC    FAR
        MOV     AX,@DATA
        MOV     DS,AX
        CALL    CLEAR                   ;CLEAR THE SCREEN
        CALL    CURSOR          ;SET CURSOR POSITION
        CALL    GETDATA         ;INPUT A STRING INTO BUFFER
        CALL    CONVERT         ;CONVERT STRING TO UPPER CASE
        CALL    DISPLAY         ;DISPLAY STRING DATAREA
        MOV     AH,4CH
        INT     21H                     ;GO BACK TO DOS
MAIN    ENDP
;---------------
;THIS SUBROUTINE CLEARS THE SCREEN
CLEAR   PROC
        MOV     BH,07                   ;NORMAL ATTRIBUTE
        MOV     CX,0000                 ;SCROLL FROM ROW=00,COL=00
        MOV     DX,184FH                ;TO ROW=18H,4FH
        INT     10H                     ;INVOKE INTERRUPT TO CLEAR SCREEN
        RET
CLEAR   ENDP
;THIS SUBROUTINE SETS THE CURSOR TO THE BEGINNING OF THE 3RD LINE
CURSOR  PROC
        MOV     AH,02                   ;SET CURSOR FUNCTION
        MOV     BH,00                   ;PAGE 0
        MOV     DL,01                   ;COLUMN 1
        MOV     DH,03                   ;ROW 3
        INT     10H                     ;INVOKE INTERRUPT TO SET CURSOR
        RET
CURSOR  ENDP
;---------------
;THIS SUBROUTINE DISPLAYS A STRING ON THE SCREEN
DISPLAY PROC
        MOV     AH,09                   ;DISPLAY STRING FUNCTION
        MOV     DX,OFFSET DATAREA       ;DX POINTS TO BUFFER
        INT     21H                     ;INVOKE INTERRUPT TO DISPLAY STRING
        RET
DISPLAY ENDP
;---------------
;THIS SUBROUTINE PUTS DATA FROM THE KEYBOARD INTO A BUFFER
GETDATA PROC
        MOV     AH,0AH                  ;INPUT STRING FUNCTION
        MOV     DX,OFFSET BUFFER        ;DX POINTS TO BUFFER
        INT     21H                     ;INVOKE INTERRUPT TO INPUT STRING
        RET
GETDATA ENDP
;---------------
;THIS SUBROUTINE CONVERTS ANY SMALL LETTER TO ITS CAPITAL
CONVERT PROC
        MOV     BX,OFFSET BUFFER
        MOV     CL,[BX]+1                       ;GET THE CHAR COUNT
        SUB     CH,CH                           ;CX = TOTAL CHARACTER COUNT
        MOV     DI,CX                           ;INDEXING INTO BUFFER
        MOV     BYTE PTR[BX+DI]+2,20H           ;REPLACE CR WITH SPACE
        MOV     SI,OFFSET DATAREA+2             ;STRING ADDRESS
AGAIN:  MOV     AL,[BX]+2                       ;GET THE KEYED-IN DATA
        CMP     AL,61H                          ;CHECK FOR 'a'
        JB              NEXT                            ;IF BELOW, GO TO NEXT
        CMP     AL,7AH                          ;CHECK FOR 'z'
        JA              NEXT                            ;IF ABOVE GO TO NEXT
        AND     AL,11011111B                    ;CONVERT TO CAPITAL
NEXT:   MOV     [SI],AL                         ;PLACE IN DATA AREA
        INC     BX
        LOOP    AGAIN                           ;LOOP IF COUNTER NOT ZERO
        RET
CONVERT ENDP
        END     MAIN