more or less

If a file is too long to display in a window, you should use the more command instead of the cat command to display its contents. If you don't have a long file in your directory, let's find one to practise with. Try the file /usr/include/math.h. Do

   more /usr/include/math.h
You will see one page full. To advance to the next screen, hit the spacebar. To advance one line, hit Enter. To back up one page (provided more isn't finished with the file), hit the b key. To quit, type q or Ctrl-c. The command less does pretty much the same thing, but doesn't automatically quit when you reach the end of the file. Some folks prefer it this way.