good to know that i started with the "wrong" one.
It's not the wrong one. Lite-C is just more powerfull and the future of 3dgs. On the other hand you have a lot more possibilites in lite-c to mess things up. You'll remember these words next time you overwrite random parts of your memory or get somehow lost with pointers. ;-)
is the SED a good thing to learn lite-c.
Give it a try. SED ist not the top of editors but sufficient for the beginning and has the advantage of displaying the helpfile directly. If you used SED for a time and find it doesn't fit your needs switch to another editor. You can use almost any text editor you like. However, sometimes you'll rely on SED, i.e. for debugging purposes.
