To uppercase

.MODEL SMALL
.386
.STACK 4096



.DATA
Prompt      db  "Enter a string: ", '$'

;-------------------------Variables---------------------------
;STRLENGTH  db      254             ;Max amount of characters
STRLENGTH   db      254         ;Allocated space
STRCHAR     dw      ?           ;Will be filled with amount of characters entered
INPUTBUFF   db      254 dup(?)      ;The buffer that will contain the input
;PRINTBUFF  db      256 dup(?)      ;dup(?) pretty much means you want 254 bytes of something
;OUTPUTBUFF db      254
;SHAREDBUFF     dw      ?
LINEFEED    db      13, 10, '$'




;------------------------Code Segement------------------------
.CODE

;=========================================================================================================
MAIN        PROC
            .STARTUP

            ;Here we would call the other procs to carry out the comparing, etc
            ;------------------------Display Prompt------------------------
            MOV     AH, 9                   ;Print Function
            MOV     DX, OFFSET Prompt       ;Address for prompt
            INT     21h                     ;DOS Call

            MOV     AH, 0Ah                 ;Input Function
            MOV     DX, OFFSET STRLENGTH    ;Start of buffer
            INT     21h                     ;DOS Call


            CALL    BUFFERCOPY


            .EXIT
MAIN        ENDP
;=========================================================================================================

;---------------Copys original string to a "shared" buffer and terminates the copy with a '$'-----------
BUFFERCOPY  PROC

            ;------------Adding $ to end of chars inputted------------
            MOV     SI, OFFSET STRLENGTH + 1    ;Pointing to numbers of chars entered
            MOV     CL, [ SI ]                  ;Moving length to CL
            MOV     CH, 0                       ;Clearing CH to use CX
            INC     CX                      ;Incrementing to get to last character
            ADD     SI, CX                      ;SI now points to address of enter key (chr(13))
            MOV     AL, '$'                     ;Moving $ into AL
            MOV     [ SI ], AL                  ;Replacing last character (chr(13)) with $

            ;-------NEW LINE-------
            MOV     AH, 9
            MOV     DX, OFFSET LINEFEED
            INT     21h

            CALL    PRINTBUFFER
            CALL    LOWERCASE

            RET
BUFFERCOPY  ENDP



;--------------Lowercase the shared buffer (convert to lowercase)-----------------
LOWERCASE   PROC
            ; To convert lowercase to uppercase, zero out the 5th bit

            ; Check for lowercase letter
            MOV     SI, 0                       ;Zero out SI
            MOV     SI, OFFSET STRLENGTH + 2    ;Move address of first character entered into SI
            MOV     BL, [ SI ]                  ;Move the contents of that address into BL
            JMP     COMPARE

COMPARE:
            MOV     BL, [ SI ]
            CMP     BL, 'a'                     ; Comparing binary value of a and typed character
            JB      NEXTCHAR                    ; If below, its not lowercase
            CMP     BL, 'z'                     ; Comparing binary value of z and typed character
            JA      NEXTCHAR                ; If above, its not lowercase
            JMP     @F

;NOT_LOWERCASE:
            ;RET


@@:         ;Might need to rever BL back to SI
            SUB     BL, 20h                     ; Subtracts 00100000 from whatever value it is working with. This zeroes out the fifth bit
            MOV     STRLENGTH[ SI ], BL         ; Move the result of previous instruction into where the address of SI is pointing to in regards to STRLENGTH
            INC     SI                          ; Increments SI to next characters address
            CMP     SI, '$'                     ; Compares terminator $ with current character held in SIs pointer address
            JE      @F                          ; If it is a $, it jumps to next @@ which starts new linefeed and CALLs PRINTBUFFER
            JMP     COMPARE                     ; If it is not a $, it jumps to COMPARE label


NEXTCHAR:
            INC     SI
            CMP     SI, '$'
            JE      @F
            JMP     COMPARE

            ;MOV    SI, 0
            ;MOV    CX, STRCHAR


@@:
            ;-------NEW LINE-------
            MOV     AH, 9
            MOV     DX, OFFSET LINEFEED
            INT     21h

            CALL    PRINTBUFFER

            RET
LOWERCASE   ENDP

END