A book introducing the writing of programs for the Commodore Pet series of computers and providing a number of pre-written subroutines (or parts of such programs) that can be combined in a variety of ways to create more complex programs.
The pre-written subroutines are incorporated in the book as 'print-outs' - ie as they would be seen if printed from the computer - and were also provided digitally on a 5.25" floppy disk.
The book contains explanations as to what the subroutines are and how they work.