Epson Apex-80 - Manual (Page 47)

Page Layout and Other Commands
The remaining commands in the Command Summary are not
normally needed when using commercial software. You may need some
of them if you are using a printer installation program provided with
an application package, but most deal with features (such as tabs,
margins, and line spacing) that are provided directly by commercial
programs and are therefore only useful to you if you want to program
the printer using a programming language such as BASIC.
Apex80 Printer Features 4-5