main:
    mov ah, 10h             ; get key
    int 16h                 ; int
    cmp ah, enter           ; enter leaves
    jz envset               ; so leave
    skip:
    cmp ah, 2Bh             ; backslash
    jz invalid
    cmp ah, 33h             ; comma
    jz invalid
    cmp ah, 34h             ; period
    jz invalid
    cmp ah, 39h             ; spacebar
    jz invalid
    cmp ah, 56h             ; the | \ key?
    jz invalid
    cmp ah, 50h             ; the 311 key. (down)
    jz invalid
    cmp ah, 48h             ; Shania Twain (up)
    jz invalid
    cmp ah, 0Eh             ; oops! you made a mistake!
    jz bkspc                ; (backspace)
    cmp ah, 4Bh             ; left arrow
    ;jz arrlef              ; on second thought
    jz invalid              ; the arrows need more
    cmp ah, 4Dh             ; right arrow
    ;jz arrrt               ; because backspace after
    jz invalid              ; you arrow breaks shit
    cmp cl, 8               ; 8 character maximum
    jz invalid              ; and it wasn't special
    cmp al, 5Ah             ; lower case?
    jbe writemem            ; skip if not
    sub al, 20h             ; convert to uppercase
writemem:                   ; now you're UPPERCASE!
    mov [ds:si], al         ; write memory
    inc si                  ; it's no longer lodsb
    call screen             ; update screen
    inc cl                  ; increase counter
    jmp main                ; loop up


bkspc:                      ; you made a mistake? crap.
    cmp cl, 0               ; if we're zero
    jz invalid              ; we have nothing to delete
    dec si                  ; move memory pointer back
    dec dl                  ; remove one column
    dec cl                  ; delete a keystroke
    xor al, al              ; load a null
    call uppos              ; update screen position
    mov [ds:si], al         ; null the byte but don't inc si
    call screen             ; run screen routine to blank spot
    dec dl                  ; now back up a column again
    call uppos              ; update position again
    jmp main                ; go back to main (again)

invalid:
    mov ah, 0eh             ; charcter display
    mov al, 07h             ; ring the bell
    int 10h                 ; DING!
    jmp main                ; do nothing and start over!!!

screen:                     ; full manual control
    push cx                 ; push cx/count out (1)
    mov cx, 1               ; move 1 in to cx
    mov bl, 07h             ; bl holds attribute
    mov ah, 09h             ; bh already set, set func
    int 10h                 ; call interrupt
    pop cx                  ; welcome back count (1)
    inc dl                  ; inc column
uppos:                      ; can call from keychk subs!
    mov ah, 02h             ; set cursor
    int 10h                 ; position int
    ret                     ; bye