A system reference manual for the Data General Corporation Nova, Supernova, Nova 1200 series, Nova 800 series, and Supernova SC mini computers. This issue is revision 07 published in February, 1974. Chapter 1 explains the programming and operation of the Nova line computers, discusses the general characteristics of these computers, the formats of the instructions they use, the perpherals and software available with them. Chapter 2 describes the central processor in detail. Chapters 3 through 7 describe the various types of periphal input / output equipment. The appendices provide information on interfacing and installation and contain a number of reference tables. This reference manual defines in detail how the central processor or a peripheral device functions, exactly what its instructions do, how it handles data, and what its control and status information means. The programming is given in machine language. Although the basic instruction and device mnemonics defined by the assembler are used, the manual is completely self-contained. No knowledge of the assembler or any other Data General Corporation software is required. The first three sections of Chapter 2, which treat the three classes of Nova-line instructions, also give the conventions needed to program the computers and understand the examples given in the text.