.BAT, .CMD, and .BTM Files

A batch file can run in two different modes.  In the first, traditional 
mode, each line of the batch file is read and executed individually.  In 
the second mode, the entire batch file is read into memory at once.  The 
second mode can be 5 to 10 times faster, especially if most of the 
commands in the batch file are internal commands.  However, only the first 
mode can be used for self-modifying batch files (which are rare), or for 
batch files which install memory-resident utilities under DOS. 

The batch file's extension determines its mode.  Files with a .CMD 
extension are run in the slower, traditional mode.  Files with a .BTM 
extension are run in the faster, more efficient mode.  You can change the 
execution mode inside a batch file with the LOADBTM command.