Environmental Variables – How Important??

To a geek like me the term Environmental variables (EV) is not new but even an average computer user is unaware of what they are and their importance. I have seen people working with computer for years still not realising that they are making use of them day in day out.
EV’s are not limited to Windows OS but are part and parcel of every OS such as UNIX, Linux, DOS (Disk Operating System).

If you have ever done programming then you must aware of term global variables well EV are the same in respect to OS. EV's are variables at OS level containing important information that is used by different software’s installed in the OS. Examples where EV comes into picture are as following

Click on Start Menu -> Run and type Notepad.exe

Windows makes use of EV called ‘Path’ whenever you write a command in Run Field. It will search for the program that you have mentioned in the Path EV and if it is able to find it there, it will execute it.

You can see the value of Path EV by going to command prompt and typing ‘Path’ there.

You can set path using a command called ‘Set’ again from command prompt.

On Command prompt type
set Path=”the path you want to set”

This will overwrite the older path if you want to retain the old path then write the following command

Set path=%path%;”the path you want to set”

To see the complete list of EV on Command Prompt Type Set

In windows you can see environmental variables by following method
Right Click My Computer => Properties => Advanced Option => EV

There are two types of EV’s

• System: Those are applicable to all the users of system
• User: Those are applicable only to the user by which they are created.

List of important EV and their description is as following

SystemDrive= The drive on which Windows is installed
SystemRoot= Folder in which Windows is installed
TEMP=Path to temporary directory
USERDOMAIN=Name of the Domain
USERNAME=Username who has logged in
USERPROFILE=Path to user profile
Windir= directory in which windows is installed
CLASSPATH= path for java class files
HOMEDRIVE=Home drive of user
HOMEPATH=Where user data residesPath=path to various locations
These might vary between different version of windows