Deleting Variables

[cyrille de brébisson]

Hello,

You are partially correct.

They are n types of variables in prime.

System wide A, B, C.... They are accessible from anywhere, anytime, non erasable, and of fixed type. To this, you can add system configurations variables such as TOff, HAngle... The purpose of these vars is for quick math, conserving values when switching from one context to another one (and of course system configuration).

User created system wide variable. They behave and act like the system wide, but are NOT of fixed type and can be deleted (through the memory interface of DelVars). These are designed to let the user create variables with his preferred names when working on a problem.

User created program variable. They can be of 2 sub-types. Exported or not. They are created when the program is compiled and last until the program is erased, or modified. They too behave like system wide variable, but are not of fixed type.
These are designed for the programmer as program global variables, to allow the program keep data in between calls and to let the programmer/user pairs exchange configuration information.

A special note here to talk about program local variables. These are only available when a program is running, and only in the block where it was declared (and it's sub blocks within the function).

Then, we get to apps. Any app variable (with the notable exception of the F1 and similar vars) are NOT accessible when the app is not active (unless fully qualified as in used with app_name.var_name). This can be confusing as 2 or more apps can have variables using the same name, but the current's app one will be used.
Once again they come in 3 flavors: System (ie,the vars that are build in, not erasable, usually of fixed type, sometimes used for configuration (XMin for example)).

Add to this User create app variables (Created/deleted using AVars DelAVars) which are like system wide user variables, but are only active (unless fully qualified) when the app is active.

And finally the user created app program. Same deal as with program variables, BUT app limited.

And this is all for the home screen.
Then we have the CAS variables. These are much more like mathematical variables. In the fact that you do not need to declare them. You can either use a variable name as an identifier (ie a name that is NOT a placeholder for a given math object, but just a random operand), or a variable (ie: a name that is a placeholder for a given math object, number that might change but which does exists). They are system wide, and usually lowercase.

I hope that this helps (although it will most likely confuse you even more at first).
Please do understand that each of these variables have their own use and 'raison d'être' and are there for a very good reason. They do represent various concepts, uses and needs. But yes, it can be confusing at first.

Cyrille