UNIX was originally written for people using teletype (hardcopy) terminals. The fewer the number of characters typed the better. For that reason, many UNIX commands are very short: two or three letters. The options, called flags, are also very short: usually one character.
The syntax for some commands will be described in this chapter along with some of the options, or flags. However as this is only an introduction to UNIX, many flags for many commands will NOT be mentioned. It is the user's responsibility to verify which flags/options are available on their machine.
Short commands are usually not very mnemonic. But there are always tricks to help remember them.