                       ENVIRONMENT VARIABLES

Environment variables which have previously been defined in the DOS
environment space by the SET command or other programs can be referenced in
BATCH files by prefixing and suffixing the defined name with a per cent sign
(%). If a variable is SET during the execution of a BATCH file, the value
is preserved until the variable is reSET, except in the case of a BATCH file
executed by COMMAND /C or CALL. All DOS environment space changes made by 
such a BATCH file are lost when it EXITs.

Every occurrence of %NAME% in a BATCH file will be replaced by the value of
the variable NAME. The name of a variable may appear anywhere in the BATCH
file, and can be used to insert filenames, commands to be executed, or 
strings to be searched for in the BATCH file. The value can have spaces. The
value assigned to the variable can have |, <, or > in it, if the value is
surrounded by double quotes (") when SET, but will not be interpreted as 
piping or redirection when referenced in a BATCH file.

An environment variable COMSPEC is automatically created in the DOS
environment space to save the program name from the SHELL line in the
CONFIG.SYS file. The PATH and PROMPT commands also automatically create 
variables, named PATH and PROMPT. The APPEND /E command creates a variable, 
named APPEND.

NOTE: If you ever want to include the character '%' in a batch file, in a 
message to be displayed on the screen for example, you need to include it 
twice to get it displayed once. For example, if the variable COMPLETENESS 
had been set to 100, the command

      ECHO  processing %COMPLETENESS%%% complete

in a batch file will display the message

      processing 100% complete

on the screen.
