Memory management is an important part in maintaining your calculator. Though not necessary, it can prevent you from filling what little memory you have, allow the calculator to run faster, and may prolong battery live.
Unlike computers now a days that have gigs of memory, that of the calculator is still measured in kilobytes, around 27 for the TI 83. There is no hard disk in the calculator so what memory you have is all RAM and needs a constant power supply. Don't worry about losing your memory when you change batteries though, there's a backup battery for that. As long as you leave the calculator off and don't try to run it, your memory stays in take. Note: the backup battery doesn't have the power to store memory and run the calculator, thus turning the calculator on when the batteries are out result in a memory reset, a trick I had to use many times when I did manage to crash my calculator or lock it up.
Because all of the memory is ram, you actually have less memory than you might think. While you can use every last K to store stuff, that's not a good idea. The calculator needs some of that memory just to run things. It's best to leave 2-3 K of memory free to run programs and graphs...
To access your memory: Press [2nd][MEM]
You will see 5 options: Check Ram, Delete, Clear Entries, Clear All Lists, and Reset
The second option in the MEM menu allows you to erase any variables, list, matrics, programs, or pictures from your calculator. Unfortunately, their is no undo or recycle bin as there is on your computer, once you've deleted something, you can't restore it.
You will see all the same catagories as in Check Ram in addition to All. It does as it implies and allows you to go through all of the categories at once. Whichever one you select, you will be able to scroll through it's contents in alphabitical order. The memory taken up by each item is displayed to the right.
Browsing in this method can be useful in finding the size of a peticular file or list. As usual, you can leave this menu by pressing [2nd][QUIT] or by opening another menu.
Something I personally do is to delete all of my real variable (A-Z), old lists, and miscilanious variables that may have been created by some program or game and left behind. This can clear out a little room and saves some, abet little, on battery power.
Your calculator stores a history of your Entries. Usually around the last 10, but it varies on entry size. Using this option in you memory menu can delete this history which may add up to 128 bytes. This is usually only done if you're cleaning house or don't wish someone else to see what you've been doing, such as when loaning out a calculator during a test.
This will delete ALL of your stored lists. This also clears out the lists editor. You will have to run SetUpEditor from your [STAT] menu.
There are two functions under Reset: reseting the calculator and reseting teh defaults. Reseting the calculator delets ALL of the contents and restores it the condition it was in when you first put the batteries in. It is also the bane of any student who is caught playing games in class since most teachers will delete the entire calculator, not just the game at fault (which once cost me a weeks worth of programming before i learned to frequenty backup on a friends calculator).
On the other hand, Reseting Defaults is a useful funtion. If you or someone else has messed up something on your calculator and aren't sure what, this will often correct the problem by changing all mode/window.. settings to their defaults without any memory lose.
pick another subject!