An environment block contains zero-terminated ASCII strings, each of which represents the name and value of an environment variable. Programs use environment variables for information about their operating environment. For example, a program may use the PATH variable to determine which directories to search for programs to run, or it may use the TEMP variable to determine the drive and directory in which to place the temporary files it creates. PATH>TEMP>
Each string in the environment block consists of a name, an equal sign (=), and a value, as in the following example of a typical PATH setting:
PATH=C:\DOS;C:\BIN
The content of a program's environment block is set by the program that starts it. When the command processor, COMMAND.COM, starts a program, its environment block contains at least the COMSPEC and PATH variables: COMSPEC specifies the location of COMMAND.COM, and PATH specifies the possible locations of program files and batch files. This environment block may also contain additional variables set by the user with the set command. PATH>COMSPEC>set command>