Th Topic: environment variables

Topic: environment variables

topics > computer science > data > Group: parameters

Topic:
binding of names to objects
Topic:
context
Topic:
early vs. late binding
Topic:
evaluation in an environment
Topic:
global declarations and variables
Topic:
named constants and expressions
Topic:
names defined by context
Topic:
namespace
Topic:
parameter passing by argument list
Topic:
pronoun reference
Topic:
running programs in a workspace or environment

Summary

An environment variable is a keyword-value defined external to a program. It is an implicit parameter to the program. It acts as a free variable. Environment variables are typically used for configuration.
A program may run in a workspace or environment. If so, all variables are part of the environment.
Dynamic variables are local-scope variables accessible from any procedure call. They are implicit parameters like environment variables. They avoid passing a configuration object to all procedures or using a global variable.
Bind or mount gives a file system name to a device, directory, or data object. Instead of accessing the environment, a program opens a file with a well-known name. This allows fine grain control of accessibility. (cbb 7/06)

Subtopic: configuration as environment

Quote: use environmental variables for conditions that effect the way a program runs; e.g., traffic load; use brainstorming [»musaJD3_1993]

Subtopic: free variable

Quote: the environment of an applicative expression defines values for free variables [»landPJ1_1964]

Subtopic: dynamic variables

Quote: implement dynamic variables via set and use statements that allocate from the stack; 'use' searches the 'set' variables for a match [»hansDR6_2001]

Subtopic: bind vs. path

Quote: Plan 9 uses the same name for different files/services in different processes; fundamental to system [»pikeR6_2000]
Quote: bind rearranges the name space for a process; e.g., replace PATH by binding directories to /bin; same as mount
[»pikeR6_2000]

Related Topics

Topic: binding of names to objects (19 items)
Topic: context (8 items)
Topic: early vs. late binding (15 items)
Topic: evaluation in an environment (35 items)
Topic: global declarations and variables (33 items)
Topic: named constants and expressions (21 items)
Topic: names defined by context (36 items)
Topic: namespace (19 items)
Topic: parameter passing by argument list (6 items)
Topic: pronoun reference (23 items)
Topic: running programs in a workspace or environment
(14 items)