;Program: Input a group of characters (a word) from the terminal.
;         - The program converts each character to a binary nunber, 
;            (where A=1, B=2, C=3....Z=26)
;         - The binary number is then added to an accumulator.  
;         - When the Accumulator = 100, you WIN!! 
;            (the 'Bell' rings and the program exits to DOS)  
;         - When the Accumulator goes over 100, you are prompted to try again.


Data Segment
Welcome_Message DB 'Welcome to "Add-the-Bytes"', 0DH, 0AH, 0AH, '$'  

Intro_Message   DB 0DH, 0AH, 'Enter a word whose "Value" is 100, where:'
                DB 0DH, 0AH, 'A=1, B=2, C=3...Z=26...{Note: STRESS = 100}' 
                DB 0DH, 0AH, 0AH, '$'    ;Note: Message on 3 lines

Error_Message   DB 007, ' <--- ?Error...Sum Exceeds 100, try again!...'
                DB 0DH, 0AH, 0AH, '$'    ;Error-Message

Error_Message2  DB 0DH, 0AH, 007, '  ^--- ?Error...Sum is Below 100, try again!'
                DB 0DH, 0AH, 0AH, '$'    ;Error-Message

Bad_Character   DB 007, ' <--- ?Char.Entered NOT A<>Z ?', 0DH, 0AH, '$'

Exit_Message    DB 007, ' <--- "A WINNER!" {Sum 100 = Exit to Dos}', 007 
                DB 0DH, 0AH, 007, '$'   ;Note: 007 = Bell

Bye_Message DB 0DH, 0AH, 'Thanks for using "Add-the-Bytes"...have a nice day!'
            DB 0DH, 0AH, '$'
Data EndS
;------------------------------
Working_Storage Segment Stack
  DW 100H    DUP (?)
Working_Storage EndS
;------------------------------
Code Segment
     Assume CS:Code, DS:Data, SS:Working_Storage

Prog_Start: Mov AX,Data             ;Init
            Mov DS,AX               ;Data Segment Pointer

            Mov  DX, Offset Welcome_Message
            Mov  AH,9               ;String write to DOS
            Int  21H                ;Write it

P_Loop:     Mov  AH,9               ;String write to DOS
            Mov  DX, OffSet Intro_Message
            Int  21H                ;Write it
            Mov  CH, 0              ;Clear CH..our Byte Sum Accumulator

Get_Chr:    Mov  AH,1               ;Read a single char.from keyboard
            Int  21H                ;Get char. from DOS....Int = Interrupt 
            
   ;Make sure character is =>A & =<Z
            Cmp  AL,'A'             ;Check it against 'A'
            JB   NG                 ; Less than (Below) 'A', Jump to NG:
            Cmp  AL,'Z'             ;Check it against 'B'
            JA   NG                 ; Greater than (Above) 'Z', Jump to NG:
   ;Ok, the character entered is between A<->Z

            Sub  AL,40H             ;40H = the ASCII Char.just before 'A',
                                    ; so this makes A=1, B=2, C=3 & Z=26
            Add  CH,AL              ;Add binary result to CH
            CMP  CH, 100            ;Check interim result against 100
            JZ   Winner             ; Yes, word = 100
            JA   Oops               ; No...and you went over 100!
            Jmp  Get_Chr            ;go get another character...

Oops:       Mov  DX, OffSet Error_Message
            Mov  AH,9               ;Sorry...Sum > 100
            Int  21H
            Jmp  P_Loop             ;go try another word....

Winner:     Mov  DX, OffSet Exit_Message
            Mov  AH,9
            Int  33
            Mov  DX, OffSet Bye_Message
            Int  33
            Mov  AX,4C00H           ;setup for return to DOS
            Int  21H                ;...do it!
;You have gone back to DOS with the above Interrupt!

NG:         Cmp  AL, 0DH            ;See if char.entered is <CR>
            JZ   Word_End           ;Yes...go tell them error...

            Mov  DX, OffSet Bad_Character
            Mov  AH,9
            Int  33                 ;type out error message
            Jmp  P_Loop             ;Go try another word!

Word_End:   Mov  DX, OffSet Error_Message2
            Mov  AH,9
            Int  33                 ;Tell user sum is too low
            Jmp  P_Loop             ;Go try another word!
Code EndS
End Prog_Start