Preliminaries on Categories, Abelian Groups and Homotopy

Abstract

The purpose of this chapter is to provide the reader of the book with quick references to the subjects of the title. The content is motivated by the needs of later chapters, and not by intrinsic considerations. The reader should have some elementary knowledge of categories and abelian groups; otherwise he might find the treatment too concise. But even with very little knowledge he should probably start the reading with Chapter II, and refer to Chapter I only when necessary. He may then find the reference in I too short, insufficient (some proofs are omitted), or too ad-hoc; in that case he should consult the relevant literature, samples of which are listed at the end of §1 and §2.