Differentiating Between Local and Global Variables

Differentiating Between Local and Global Variables

This lesson discusses the use of local variables versus global document variables.
Global variables are accessible by all functions loaded within a document (or drawing).
These variables may retain their value after the program that defined them completes.
Sometimes, this is what you want. You’ll see an example of this later in the tutorial.

Local variables retain their value only as long as the function that defined them
is running. After the function finishes running, the local variable values are automatically
discarded, and the system reclaims the memory space the variable used. This is known
as automatic garbage collection, and is a feature of most LISP development environments,
such as Visual LISP. Local variables use memory more efficiently than global variables.

Another big advantage is that local variables make it easier to debug and maintain
your applications. With global variables, you are never sure when or in which function
the variable’s value might be modified; with local variables you do not have as far
to trace. You usually end up with fewer side effects (that is, one part of the program
affecting a variable from another part of the program).

Because of the advantages cited, this tutorial uses local variables almost exclusively.

NOTE:If you have been working with AutoLISP for some time, you may have developed the practice of using global variables during
development to examine your program while you are building it. This practice is no
longer necessary, given the powerful debugging tools of Visual LISP.

Learning AutoCad

sp>Local Variables: declared and used inside a function (scope). it's not possible to use a local variable outside it's function. Global variables: declared outside all function, can be accessed by all functions. … And you can declare variables which life time is limited to the scope they were declared in.Local variable – declared within subroutines or programming blocks, their local scope means … What is the difference between a global and a local variable?Global variables are declared outside any function, and they can be accessed (used) on any function in the program. Local variables are declared inside a function, and can be used only inside that function. It is possible to have local variables with the same name in different functions.… A variable is a memory location inside memory which is referred using a name. The value inside a variable changes throughout the execution …… Local vs Global Variables Global variables can be used anywhere in a computer program. This means that global variables can be used in …… Here, a,b, and sum are local variables which are declared in main function. Example of global variable. //program to find the sum and difference …Global variable – declared at the start of the program, their global scope means they can be used in any procedure or subroutine in the program …local variables versus global document variables. Global variables are accessible by all functions loaded within a document (an …differences between local variables and global variables in c programming language, how local and global scope is used in c language?… This content precisely describes the difference between local variable and global variable. Local Variable are always declared inside a function …

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