An example of this is the more command. This is how the man pages are displayed. Many users felt that this was too inflexible and along came another command found on many UNIX systems called less . The less command is essentially the same as the more command with the exception that it allows the up and down arrow keys to be used to scroll around a document. Many of the UNIX commands may be well known to the user while others may not.
Some examples are ls, cd, grep, find and chmod to name just a select few.
It is important to realize that while these commands might vary in syntax and usage somewhat from one platform of UNIX to another, they are shell independent. Whether in the C shell or the Z shell, the grep command behaves the same. Remember to see how a particular command is used on a particular platform, the user can use the man command. These are commands that are local to the particular shell. Some examples of these are the history command in the C shell, and the export in the Bourne shell.