TV keeps all its data in RAM. This means, that on the one hand the maximum
file-size is limited by the amount of memory you have installed, but on the
other hand the speed of operation is high. If you really need to edit files
larger than your memory allows, you can always install a program that lets
you use virtual memory (a part of your harddisk, used as if it were RAM).

The amount of memory used for a file is the size of the file, with an extra
1k initially. When your file grows during an edit-session, this 1k is used
until it is full. When that happens, the required new amount plus another
1k is added. At that moment, the total amount of memory required is over
TWICE the size of your file! Immediately after expanding, TV releases the
half that is no longer required. So, if you have 4M RAM available, it is
not practical to edit files larger than 2M. When TV reports a memory
problem, it is a good thing to keep this in mind, because otherwise you
might think TV is talking rubbish.

When your file shrinks, memory is NOT returned. That is done only when the
buffer becomes completely empty.