.org 100h
mloop:
    ;draw underscore to screen
    mvi a, 0x5F
    out 4
tloop:
    ;check buffer
    in 0
    cpi 1
    jnz tloop

    ;remove underscore
    call remlet

    ;put character out
    in 1
    mov b, a
    ;b now has our input
    cpi 0x08
    jnz skip1
    ;if backspace, remove a letter
    call remlet
    jmp mloop
skip1:
    mov a, b
    cpi 0x09
    jnz skip2
    ;if tab, put a couple spaces in
    mvi a, 0x20
    out 4
    out 4
    jmp mloop
skip2:
    mov a, b
    cpi 0x0D
    jnz print
    ;if enter, go to new line
    in 3
    inr a
    out 3
    xra a
    out 2
    jmp mloop

print:
    out 4

    ;check if at end of screen
    in 3
    cpi 24
    jnz mloop
    in 2
    cpi 40
    jnz mloop

    ;if we are, reset the vram address
    xra a
    out 2
    out 3

    ;loop back
    jmp mloop


remlet:
    call backlet
    mvi a, 0x00
    out 4
    call backlet
    ret

backlet:
    ;moves the current vram position back one
    ;load the current position
    in 2
    sui 1
    out 2
    ;if FF subtract one from y position
    jnc exit
    mvi a, 39
    out 2
    in 3
    sui 1
    out 3
    jnc exit
    mvi a, 24
    out 3
exit:
    ret