 global variables - meaning and definition. What is global variables
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# What (who) is global variables - definition

COMPUTER PROGRAMMING, A VARIABLE ACCESSIBLE THROUGHOUT A COMPUTER PROGRAM
Global variables; Global environment; Global state (computing); Superglobals; Common data; Comparison of programming languages (global variables)

Global variable
In computer programming, a global variable is a variable with global scope, meaning that it is visible (hence accessible) throughout the program, unless shadowed. The set of all global variables is known as the global environment or global state.
free variable
• CLASSIFICATION OF VARIABLES IN A LOGIC FORMULA BASED ON WHETHER OR NOT THEY ARE INSIDE THE SCOPE OF A QUANTIFIER
Free variable; Bound variable; Variable binding operation; Variable-binding operation; Free variables; Bound variables; Unbound variable; Unbound variables; Variable-binding operator; Variable binding operator; Free and bound variables; Bound variable clash; Free and bound variable; Placeholder (computer programming); Free variables & bound variables; Free occurrence; Placeholder variable; Apparent variable
1. A variable referred to in a function, which is not an argument of the function. In lambda-calculus, x is a {bound variable} in the term M = x . T, and a free variable of T. We say x is bound in M and free in T. If T contains a subterm x . U then x is rebound in this term. This nested, inner binding of x is said to "shadow" the outer binding. Occurrences of x in U are free occurrences of the new x. Variables bound at the top level of a program are technically free variables within the terms to which they are bound but are often treated specially because they can be compiled as fixed addresses. Similarly, an identifier bound to a recursive function is also technically a free variable within its own body but is treated specially. A closed term is one containing no free variables. See also closure, lambda lifting, scope. 2. In logic, a variable which is not quantified (see quantifier).
bound variable
• CLASSIFICATION OF VARIABLES IN A LOGIC FORMULA BASED ON WHETHER OR NOT THEY ARE INSIDE THE SCOPE OF A QUANTIFIER
Free variable; Bound variable; Variable binding operation; Variable-binding operation; Free variables; Bound variables; Unbound variable; Unbound variables; Variable-binding operator; Variable binding operator; Free and bound variables; Bound variable clash; Free and bound variable; Placeholder (computer programming); Free variables & bound variables; Free occurrence; Placeholder variable; Apparent variable
1. A bound variable or formal argument in a function definition is replaced by the actual argument when the function is applied. In the lambda abstraction x . M x is the bound variable. However, x is a free variable of the term M when M is considered on its own. M is the scope of the binding of x. 2. In logic a bound variable is a quantified variable. See quantifier.