function toupper(ch)
    if (string.byte(ch) >= string.byte("a"))
        and (string.byte(ch) <= string.byte("z")) then
        return string.char(string.byte(ch) + string.byte("A")
                           - string.byte("a"))
    else
        return ch
    end
end

function tolower(ch)
    if (string.byte(ch) >= string.byte("A"))
        and (string.byte(ch) <= string.byte("Z")) then
        return string.char(string.byte(ch) + string.byte("a")
                           - string.byte("A"))
    else
        return ch
    end
end

function test(x)
	print(x .. " " .. toupper(x) .. " " .. tolower(x))
end

test("a")
test("A")
test("m")
test("M")
test("z")
test("Z")
test("1")
test(",")