For example, if the stack looks like this:

then

→a creates local variable a = 20.

→ab creates local variables a = 6 and b = 20.

→abc creates local variables a = 10, b = 6, and c = 20.

The defining procedure then uses the local variables to do calculations.

Local variable structures have these advantages:

The → command stores the values from the stack in the corresponding variables — you don’t need to explicitly execute STO.

Local variables automatically disappear when the defining procedure for which they are created has completed execution. Consequently, local variables don’t appear in the VAR menu, and they occupy user memory only during program execution.

Local variables exist only within their defining procedure — different local variable structures can use the same variable names without conflict.

Example: The following program SPHLV calculates the volume of a spherical cap using local variables. The defining procedure is an algebraic expression.

 

Level 2

Level 1

→

Level 1

 

 

 

 

 

 

 

 

 

r

h

→

volume

 

 

 

 

 

 

 

 

 

 

 

 

Program:

 

Comments:

 

 

 

 

 

 

 

 

 

«

 

 

 

 

 

 

→ r h

 

Creates local variables r and h for the radius

 

 

 

of the sphere and height of the cap.

'1/3*π*h^2*(3*r-h)'

Expresses the defining procedure. In this

 

 

 

program, the defining procedure for the local

 

 

 

variable structure is an algebraic expression.

→NUM

 

Converts expression to a number.

»

 

 

 

 

 

 

`OSPHLVK

 

Stores the program in variable SPHLV.

 

 

 

 

 

 

 

Now use SPHLV to calculate the volume of a spherical cap of radius r =10 and height h = 3. Enter the data on the stack in the correct order, then execute the program.

10 `3

J%SPHLV%

1-8 RPL Programming