diff --git a/sasm.lua b/sasm.lua
index d14da21..394072c 100644
--- a/sasm.lua
+++ b/sasm.lua
@@ -18,6 +18,23 @@ insc.sub = 4090
 insc.jmp = 4089
 insc.sez = 4088
 
+local f=io.open("ins.def","rb")
+local c = "";
+if f then
+ c=f:read("*a")
+ f:close()
+ insd,insc = {}, {}
+ for l in c:gmatch("(.+)\n") do
+  lt = {}
+  for w in l:gmatch("%S+") do table.insert(lt,w) end
+  insc[lt[2]] = tonumber(lt[1])
+  insd[tonumber(lt[1])] = lt[2]
+ end
+end
+
+if not tArgs[2] then
+ error("requires a file argument and a compile/decompile flag")
+end
 f = io.open(tArgs[2],"rb")
 if not f then error("file inaccessable") end
 c = f:read("*a")