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A variable that is bound inthe current environment. When evaluating an expression insome environment, the evaluation of a variable consists oflooking up its name in the environment and substituting itsvalue.Most programming languages have some concept of an environmentbut in Unix shell scripts it has a specific meaningslightly different from other contexts. In shell scripts,environment variables are one kind of shell variable. Theydiffer from local variables and command line arguments inthat they are inheritted by a child process. Examples arethe PATH variable that tells the shell the file systempaths to search to find command executables and the TZvariable which contains the local time zone. The variablecalled "SHELL" specifies the type of shell being used.These variables are used by commands or shell scripts todiscover things about the environment they are operating in.Environment variables can be changed or created by the useror a program.To see a list of environment variables type "setenv" at thecsh or tcsh prompt or "set" at the sh, bash, jshor ksh prompt.In other programming languages, e.g. functional programminglanguages, the environment is extended with new bindings whena function's parameters are bound to its actualarguments or when new variables are declared. In ablock-structured procedural language, the environmentusually consists of a linked list of activation records.