ERRORLEVEL [<rel>] <number>

     In PTS-DOS environment any external (for the Shell) command has a
so-called exit code - a number from 0 to 255. This code enables external
components of the executed program to detect errors made during the program
run and return error messages.

     As a rule, in case of a successful run the exit code is equal to 0, and
in case of an error - not equal to 0. The program terminated by the user (to
prevent a critical mistake, by pressing [Ctrl-Break] or [SysReq], etc.) has
the code equal to 255. But this does not mean that any program with exit
code 255 has been expressly terminated by a user.

     Usually first rate packages exit codes are described in detail in the
accompanying documents.

     Thus, ERRORLEVEL is the exit code value of the program executed last.
           <Number>   is a number from 0 to 255.

     Non-obligatory parameter <rel> is the relation described in section
"string1<rel>string2", but used here as the relation between two numerical
values of <number> and ERRORLEVEL. Its absence means that the condition is
true if the exit code is greater than or equal to <number> (i.e. ERRORLEVEL
GE <number>).

     Thus, the condition is considered to be true if the relation <rel>
between the return code and <number> is true.

Example:

     Suppose that PROGRAM.EXE is an executable program returning the exit
code.

 .....
 RUN PROGRAM.EXE
 IF ERRORLEVEL GT 5 exit
 IF ERRORLEVEL 2    echo Error code greater than or equal to 2.
 IF ERRORLEVEL EQ 1 echo Error code equal to 2.
 .....