Computercraft Basic | Advanced OS/UI Tutorial | Part 1

--Variable
local osVer = "Alpha 1.0"
local w,h = term.getSize()
local brunning = true
local slc = 0
local _mtext = 1
local _mback = 128

--Tables
local menu = {
    [""] = {tcol = _mtext; bcol = _mback; x = 1; xx = 7; y = 1; cmd = function() slc = 1 end};
    ["            "] = {tcol = _mtext; bcol = _mback; x = 1; xx = 12; y = 2; cmd = function() end};
    [" Programs > "] = {tcol = _mtext; bcol = _mback; x = 1; xx = 12; y = 3; cmd = function() end};
    [" Settings > "] = {tcol = _mtext; bcol = _mback; x = 1; xx = 12; y = 4; cmd = function() end};
    [" Lua Prompt "] = {tcol = _mtext; bcol = _mback; x = 1; xx = 12; y = 5; cmd = function() end};
    [" Quit       "] = {tcol = _mtext; bcol = _mback; x = 1; xx = 12; y = 6; cmd = function() term.setBackgroundColor(colors.black) term.setCursorPos(1,1) term.clear() brunning = false end};
    [" Shutdown   "] = {tcol = _mtext; bcol = _mback; x = 1; xx = 12; y = 7; cmd = function() os.shutdown() end};
    [" Logoff     "] = {tcol = _mtext; bcol = _mback; x = 1; xx = 12; y = 8; cmd = function() end};
    [" Reboot     "] = {tcol = _mtext; bcol = _mback; x = 1; xx = 12; y = 9; cmd = function() os.reboot() end};
    ["            "] = {tcol = _mtext; bcol = _mback; x = 1; xx = 12; y = 10; cmd = function() end};
}
--Functions
local function tb_Draw()
    term.setCursorPos(1,1)
    term.setBackgroundColor(8)
    term.setTextColor(1)
    term.clearLine()
    print("[Begin]")
    term.setCursorPos(math.floor(w)-#osVer, 1)
    print(osVer)
end

local function clear(bcol)
    term.setBackgroundColor(bcol)
    term.clear()
end

local function drawMenu()
    for k,v in pairs(menu) do
        term.setBackgroundColor(v.bcol)
        term.setTextColor(v.tcol)
        term.setCursorPos(v.x, v.y)
        print(k)
    end
end

local function menuClick()
    for k,v in pairs(menu) do
        if  e[1] == "mouse_click" then
            if e[2] == 1 then
                if e[3] >= v.x and e[3] <= v.xx and e[4] == v.y then
                    v.cmd()
                    else slc = 0 clear(colors.black) tb_Draw()
                end
            end
        end
    end
end

--Main code
clear(colors.black)
tb_Draw()
while brunning do
e = {os.pullEvent()}
    if slc == 0 then
        clear(colors.black)
        tb_Draw()
        if  e[1] == "mouse_click" then
            if e[2] == 1 then
                if e[3] >= 1 and e[3] <= 7 and e[4] == 1 then
                    slc = 1
                    drawMenu()
                end
            end
        end

    elseif slc == 1 then
        drawMenu()
        menuClick()
    end
end