Information in memory can be moved very quickly and easily. If we want to change a word in a document, what happens in the computer is something like this:
Imagine Darlene has started out her resume with the following word:
REUME
Obviously she has forgotten a letter. If she were using a typewriter, the page would be trashed, and she would have to start over. Since this is a word processor, Darlene can manipulate the memory containing codes for the word "REUME" and add the "S" to it. When she tries, the following things happen:
She moves her cursor to the spot in the text where she wants the S to show up. The "cursor" is a special mark on the screen that indicates at which place in the document the computer is currently focused. In this case, Darlene wants to put an S between the E and the U. Her word processor won't let her put the cursor between two letters (although some will), so she puts it on the U.
By moving the cursor, Darlene is telling the program to move around in memory as well. When she place her cursor on the U on the screen, she is telling the program to point to the corresponding spot in the computer's memory. The computer is now concentrating on the memory cell that contains the code for the character "U".
She checks to be sure she is in insert mode (more on that later), and she types the letter "S".
When Darlene does this, the computer shifts all the letters one memory cell to the right, and inserts the code for the S in its proper place.