TITLE   Uppercase conversion of characters   TOUPPER.ASM
COMMENT |
        Objective: To convert lowercase letters to
                   corresponding uppercase letters.
            Input: Requests a character string from keyboard.
|          Output: Prints the input string in uppercase.
.MODEL SMALL
.STACK 100H
.DATA
name_prompt    DB  'Please type your name: ',0
out_msg        DB  'Your name in capitals is: ',0
in_name        DB  31 DUP (?)

.CODE
INCLUDE io.mac
main    PROC
        .STARTUP
        PutStr  name_prompt  ; request character string
        GetStr  in_name,31   ; read input character string
        nwln
        PutStr  out_msg
        mov     BX,OFFSET in_name  ; BX := address of in_name
process_char:
        mov     AL,[BX]      ; move the char. to AL
        cmp     AL,0         ; if it is the NULL character
        je      done         ;  conversion done
        cmp     AL,'a'         ; if (char < 'a')
        jl      not_lower_case ; not a lowercase letter
        cmp     AL,'z'         ; if (char > 'z')
        jg      not_lower_case ; not a lowercase letter
lower_case:
        add     AL,'A'-'a'   ; convert to uppercase
not_lower_case:
        PutCh   AL           ; write the character
        inc     BX           ; BX points to next char.
        jmp     process_char ; go back to process next char.
        nwln
done:                        
        .EXIT
main    ENDP
        END   main