This document explains the TUTOR language which is used by teachers to create or author lesson materials on the PLATO IV computer-based education system. After an introductory section, the second section explains how to display text and line drawings to students. The third section introduces subroutines, and it is followed by explanations of calculations in TUTOR. The fifth section discusses in detail how to build interconnections and sequences into a lesson. Conditional commands are explained in section six and section seven explains how to judge student responses. Additional display features are described in section eight and additonal calculation topics are given in section nine. Common variables are listed in section ten, and the document concludes with a miscellaneous section. Sources of further information, a list of TUTOR commands, and built-in calculation functions are provided in the appendix. (CH)