This handbook was initially conceived as a set of examples describing -- or rather illustrating -- the use of a very powerful computer program for linear programming and other computations. It is still that, but in the writing it has become much more. First, it was clear that to understand the examples, it was necessary to describe the general character of the computer program, or alternatively, to refer the reader to an outside source. The former seemed more convenient to the student and so Part III on the Design and Use of USDA LP/90 was included. Second, a handbook on a computer program for linear programming seemed incomplete without at least a resume of the theory of linear programming itself. Thus, it was decided to present in Part II such a section. However, it too grew beyond its initial bounds and became rather an elementary introduction to linear programming and several closely related subjects. The result, then, is this five-part handbook including a general Introduction (Part I), An Introduction to Linear Programming and Related Computations (Part II), The Design and Use of USDA LP/90 (Part. Ill), Sample Computations with USDA LP/90 (Part IV) and finally, A Reference Guide to the Agendum Routines (Part V). The study as a whole is part textbook and part reference manual. As such it should be useful both to beginners and experts.