Calculator

local Total, Operando = 0, ""

function Gui()
    term.setBackgroundColor(colors.black)
    term.clear()

    term.setCursorPos(1,1)
    term.write(Total)
    term.setCursorPos(1,2)
    term.write(Operando)

    --remove when done
    paintutils.drawLine(27,1,27,20,colors.white)

    --Number buttons
    paintutils.drawFilledBox(1,4,5,7,colors.yellow)
    term.setCursorPos(3,6)
    term.write("7")
    paintutils.drawFilledBox(6,4,10,7,colors.yellow)
    term.setCursorPos(8,6)
    term.write("8")
    paintutils.drawFilledBox(11,4,15,7,colors.yellow)
    term.setCursorPos(13,6)
    term.write("9")
    paintutils.drawFilledBox(1,8,5,11,colors.yellow)
    term.setCursorPos(3,10)
    term.write("4")
    paintutils.drawFilledBox(6,8,10,11,colors.yellow)
    term.setCursorPos(8,10)
    term.write("5")
    paintutils.drawFilledBox(11,8,15,11,colors.yellow)
    term.setCursorPos(13,10)
    term.write("6")
    paintutils.drawFilledBox(1,12,5,15,colors.yellow)
    term.setCursorPos(3,14)
    term.write("1")
    paintutils.drawFilledBox(6,12,10,15,colors.yellow)
    term.setCursorPos(8,14)
    term.write("2")
    paintutils.drawFilledBox(11,12,15,15,colors.yellow)
    term.setCursorPos(13,14)
    term.write("3")
    paintutils.drawFilledBox(1,16,5,19,colors.yellow)
    term.setCursorPos(3,18)
    term.write("")
    paintutils.drawFilledBox(6,16,10,19,colors.yellow)
    term.setCursorPos(8,18)
    term.write("0")
    paintutils.drawFilledBox(11,16,15,19,colors.yellow)
    term.setCursorPos(13,18)
    term.write(",")

    --Operators Buttons
    paintutils.drawFilledBox(16,4,20,7,colors.gray)
    term.setCursorPos(18,6)
    term.write("/")
    paintutils.drawFilledBox(21,4,26,7,colors.gray)
    term.setCursorPos(23,6)
    term.write("CE")
    paintutils.drawFilledBox(16,8,20,11,colors.gray)
    term.setCursorPos(18,10)
    term.write("*")
    paintutils.drawFilledBox(21,8,26,11,colors.gray)
    term.setCursorPos(23,10)
    term.write("+")
    paintutils.drawFilledBox(16,12,20,15,colors.gray)
    term.setCursorPos(18,14)
    term.write("-")
    paintutils.drawFilledBox(21,12,26,15,colors.gray)
    term.setCursorPos(23,14)
    term.write("")
    paintutils.drawFilledBox(16,16,20,19,colors.gray)
    term.setCursorPos(18,18)
    term.write("%")
    paintutils.drawFilledBox(21,16,26,19,colors.gray)
    term.setCursorPos(23,18)
    term.write("=")
end

-- Main --
while (true) do
    Gui()
    term.setCursorPos(1,1)
    local e, b, x,y = os.pullEvent()
    if (e == "key") then
        local key = keys.getName(b)

        if (key == "+") then
            operando = "+"
        elseif (key == "-") then
            operando = "-"
        elseif (key == "*") then
            operando = "*"
        elseif (key == "/") then
            operando = "/"
        else
            if (keys.getName(b) == "zero") then key = "0"
            elseif (keys.getName(b) == "one") then key = "1"
            elseif (keys.getName(b) == "two") then key = "2"
            elseif (keys.getName(b) == "three") then key = "3"
            elseif (keys.getName(b) == "four") then key = "4"
            elseif (keys.getName(b) == "five") then key = "5"
            elseif (keys.getName(b) == "six") then key = "6"
            elseif (keys.getName(b) == "seven") then key = "7"
            elseif (keys.getName(b) == "eight") then key = "8"
            elseif (keys.getName(b) == "nine") then key = "9"
            end

            if (Operando == "") then
                Total = tonumber(key)
            elseif (Operando == "+") then
                Total = Total + tonumber(key)
            elseif (Operando == "-") then
                Total = Total - tonumber(key)
            elseif (Operando == "*") then
                Total = Total * tonumber(key)
            elseif (Operando == "/") then
                Total = Total / tonumber(key)
            end
        end
    end
end