HP 48gII Graphing, 50g Graphing manual Understanding Programming, Contents of a Program

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RPL Programming

If you’ve used a calculator or computer before, you’re probably familiar with the idea of programs. Generally speaking, a program is something that gets the calculator or computer to do certain tasks for you — more than a builtin command might do. In the HP 48gII, HP 49g+ , and HP 50g calculators, a program is an object that does the same thing.

Understanding Programming

A calculator program is an object with « » delimiters containing a sequence of numbers, commands, and other objects you want to execute automatically to perform a task.

For example, a program that takes a number from the stack, finds its factorial, and divides the result by 2 would look like this: « ! 2 / » or

«

!

2

/

»

The Contents of a Program

As mentioned above, a program contains a sequence of objects. As each object is processed in a program, the action depends on the type of object, as summarized below.

Actions for Certain Objects in Programs

Object	Action
Command	Executed.
Number	Put on the stack.
Algebraic or `Algebraic`	Algebraic put on the stack.
String	Put on the stack.
List	Put on the stack.
Program	Put on the stack.
Global name (quoted)	Put on the stack.
Global name (unquoted)	Program executed.
	Name evaluated.
	Directory becomes current.
	Other object put on the stack.
Local name (quoted)	Put on the stack.
Local name (unquoted)	Contents put on the stack

As you can see from this table, most types of objects are simply put on the stack — but builtin comma nds and programs called by name cause execution. The following examples show the results of executing programs containing different sequences of objects.

RPL Programming 11