2 How to read this manual

In the following, words set in typewriter font denote file names, shell commands, environmental variables, and input records of the input file. These must be typed as shown. Variables, that is, numbers, options, etc. which must by specified by the user will be given as <<variable>>. These must be replaced by the corresponding values of the variables. Optional items are denoted by brackets, e.g., as [<<variable>>].