The C shell prompt is stored in a variable appropriately named prompt . Listing 1B shows an example that resets a C shell prompt to the same string used in the Listing 1A example. Space around the equal sign is optional with the C shell. The essence of the UNIX shell is its use as a command interpreter. It arranges for the kernel to load and execute programs on your behalf.
Commands fall into one of three classes -simple commands, pipeline commands, and commnad lists.
Commands can also be grouped into lists that execute sequentially or even conditionally. I'll delve into command lists in a future column. A simple command is one that consists of a sequence of words separated by blanks. Here, a blank is one or more consecutive space or table characters, and a word is a sequence of non-blank characters. The first word of a command line is always the command name.