Any user application programs can now be loaded into the transient program area
(TPA). If a large program requires more space, the COMMAND.COM overlay area,
located at the high-numbered memory location, can be used by the application program
as well. The COMMAND.COM programs in this area are considered transient
because they are used to execute commands, such as FORMAT, that can’t be executed
by the user when an application program is running, so they can be overlayed (or overwritten)
by other programs