The line:set path=%path%;c:\jaguar\bin
simply appends:;c:\jaguar\bin
to the end of your current PATH. So, if your current PATH was say:c:\windows;c:\windows\system;c:\bjl\bjl_uploader
after doing a:set path=%path%;c:\jaguar\bin
your new PATH would be:c:\windows;c:\windows\system;c:\bjl\bjl_uploader;c:\jaguar\bin
Note: You can type "path" (sans the quotes) to view your current path.
The lines:set rdbrc=c:\jaguar\bin\rdb.rc
set dbpath=c:\jaguar\bin
set alnpath=c:\jaguar\bin
set macpath=c:\jaguar\include
set gcc_exec_prefix=c:/jaguar/bin
setup five other environment variables, (unrelated to the PATH environment variable). Presumably these variables are needed by the program you're installing.
Note: You can view what's in the environment by typing "set" (sans the quotes). If there are a number of variables and they scroll off the top of the screen, use the command "set|more" (sans the quotes) instead.
The last line:set temp=c:
is not a good idea. For one it's missing a directory (even if it was just "\" [the 'root' directory]). Two, most people don't want a whole slew of temporary files cluttering up the root directory of drive C:. Better to leave it alone or add the following three lines to your C:\AUTOEXEC.BAT file:md c:\temp
set temp=c:\temp
set tmp=c:\temp
The first line makes sure you have a "\temp" directory on drive C: and the second two lines simply point the "temp" and "tmp" environment variables to it.