Next, you'll need a text editor, some knowledge of asm and a link program. After compiling it, you should get a .85S file you can send to your calc. Then, it's best to look at the lines told to you by the compiler and compare the instructions you wrote with a Z80 instruction reference. To start with, you need a link cable. There were even some people who built cables for a very low price.
Parallel cables are only available as homemade ones.
In case you purchased the Graph-Link, you'll receive a transmitting program with it, otherwise, you may want to get one from the ticalc.org Archive . After choosing the platform you should easily find some transmitting program. Nearly as simple as that. If so, the two objects intersect. However, if you pressed the ON key while some batteries are taken out, the memory will be reset.