Project Math - Shell Calculator In Development

--Project Math
--Variable
w,h = term.getSize()
running = true
version = "1.0a"

--Functions:
--Read/Write APIs
local function comRead()
    x,y = term.getCursorPos()
   term.setCursorPos(1,y)
   print(">")
   term.setCursorPos(3,y)
   command = read()
   return command
end

local function printCentered(str, ypos)
  term.setCursorPos(w/2 - #str/2, ypos)
  term.write(str)
end

--String API
function split(pString, pPattern)
   local Table = {}  -- NOTE: use {n = 0} in Lua-5.0
   local fpat = "(.-)" .. pPattern
   local last_end = 1
   local s, e, cap = pString:find(fpat, 1)
   while s do
          if s ~= 1 or cap ~= "" then
         table.insert(Table,cap)
          end
          last_end = e+1
          s, e, cap = pString:find(fpat, last_end)
   end
   if last_end <= #pString then
          cap = pString:sub(last_end)
          table.insert(Table, cap)
   end
   return Table
end

--Graphical Functions:

--Simple header
function drawHeader()
  printCentered("Project Math Alpha 1.0", 1)
  printCentered(string.rep("-", w), 2)
end

--Calculator Main Functions:

--Splits string, ex: 5+5 -> 5 , 5 , +
function SplitStrings(com)
    local splitPattern = nil
    local mult = string.find(com,"*")
    local div = string.find(com,"/")
    local sub = string.find(com,"-")
    local add = string.find(com,"+")

    if mult ~= nil then
        splitPattern = "*"
    elseif div ~= nil then
        splitPattern = "/"
    elseif sub ~= nil then
        splitPattern = "-"
    elseif add ~= nil then
        splitPattern = "+"
    end

    splitS = split(command,splitPattern)

    math = {
        ["num1"] = splitS[1],
        ["num2"] = splitS[2],
        ["sign"] = splitPattern
    }

end

--doing the math, ex 5+5 = 10
function Calculation()
    local awnser = 0

    if math["sign"] == "*" then
        awnser = tonumber(math["num1"]) * tonumber(math["num2"])
    elseif math["sign"] == "/" then
        awnser = tonumber(math["num1"]) / tonumber(math["num2"])
    elseif math["sign"] == "-" then
        awnser = tonumber(math["num1"]) - tonumber(math["num2"])
    elseif math["sign"] == "+" then
        awnser = tonumber(math["num1"]) + tonumber(math["num2"])
    end
    return awnser
    end

--the shell / gui
function Shell()
    drawHeader()
    print("Input your numbers or commands")
    while running == true do
        command = comRead()
        if command == "exit" then
            return
        else
            SplitStrings(command)
            awnser = Calculation()
            print("Answer = " .. awnser)
        end
    end
end
--Runs the program
term.clear()
Shell()

--Exit Screen
term.clear()
term.setCursorPos(1,1)
print("Thanks for using Project Math Alpha 1.0")
print("by nickname912")