nomainwin

    WindowWidth  = 800
    WindowHeight = 500
    UpperLeftX   =  50
    UpperLeftY   =  50

    b0 =1 '  this will be outputting 0 or 1 on D0, and toggled by the button.
    b1 =1 '  this will be outputting 0 or 1 on D1, and toggled by you pulling Status S4 pin low.

    button     #w.b1, "Toggle D0",   [toggle],   UL, 60, 20

    base   = hexdec( "&H378") 'the usual base address

    graphicbox #w.g1, 290, 50, 470, 260
    graphicbox #w.g2,  10,330, 780, 104
    texteditor #w.te,  10, 50, 240, 270

    open "Port pin tester" for window as #w

    loadbmp "mimic", "port.bmp"
    #w.g1, "down ; drawbmp mimic 0 0"
    loadbmp "ext", "external.bmp"
    #w.g2, "down ; drawbmp ext 0 0"
    #w, "trapclose [quit]"

    #w.te, "Toggle button should control D0 on the port"
    #w.te, "   and on the graphic mimic."
    #w.te, "Pulling S4 low with a switch to earth should"
    #w.te, "   do the same for S4"
    #w.te, "I'll this status bit input every second."

    #w.g1, "backcolor red ;   place 142 160 ; circlefilled 9"

[mainloop]
    timer 200, [refresh]'   check every 200/1000 second for inputs, & refresh output state
    wait
    goto [mainloop]

[refresh]
    in =inp( base +1) and hexdec( "10")
        'Note this looks at the status port whose upper 5 bits are
        '   the inputs to use. (Mask is binary 0001 0000 for S4)
        '   and it's address is 1 on from the port base address.
        '   (effectively mask with 1111 1000 and then with 0001 0000)
    if in =hexdec("10") then
        state =state or hexdec( "02")'  0000 0010 so sets D1 high
        #w.g1, "backcolor black ;   place 366  71 ; circlefilled 9"
        out base, state
        #w.g1, "backcolor black ;   place 142 160 ; circlefilled 9"
        out base, state
        #w.te, "Status line S4 pulled high."
    else
        state =state and hexdec( "FD") '    1111 1101 so pulls D1 low
        #w.g1, "backcolor red ;   place 366  71 ; circlefilled 9"
        out base, state
        #w.g1, "backcolor red ;   place 142 160 ; circlefilled 9"
        out base, state
        #w.te, "Status line S4 pulled low."
    end if
    goto [mainloop]

[quit]
  timer 0                 ' stop the timer
  unloadbmp "ext"
  unloadbmp "mimic"
  close #w
  end

[toggle]
    #w.te, "Toggle button clicked!"
    if b0 =0 then
        b0 =1
        state =state or hexdec( "01")
        out base, state
        #w.g1, "backcolor red ;   place 398 71 ; circlefilled 9"
    else
        b0 =0
        state =state and hexdec( "FE")
        out base, state
        #w.g1, "backcolor black ; place 398 71 ; circlefilled 9"
    end if
    goto [mainloop]