Section 10
Programming with ALPHA Strings
One of the greatest utilizations of the HP-41C ALPHA capability is in programs that you write. ALPHA strings (a series of ALPHA characters) in your programs can prompt you for information, inform you of the status of a program and even label output. This section shows you how to use ALPHA strings in your programs.
Using ALPHA Strings in Your Programs
You can use ALPHA string in many different ways in your programs, and there are certain ways that these strings change what you see in the display while a program is running.
For example, you can place an ALPHA string in a program and instruct the program to display that string with AVIEW . The ALPHA string that you input as a line in the program is placed into the ALPHA register. AVIEW then places the contents of the ALPHA register into the display. As program execution progresses, the display continues to display the string until the program clears the string from the display, or you place a new string into the display.
Any time a program places an ALPHA string into the display, that string replaces the   program execution symbol. When the program clears the display or the program is interrupted, the   returns to the display. Regardless of what is displayed, the PRGM annunciator is always displayed during a running program.
The maximum length of an ALPHA string on any one line in a program is 15 characters. However, using APPEND ( g K in ALPHA mode), you can construct strings of up to 24 characters. Key in the first 15 characters in the string, press APPEND and then key in the remainder of the characters. The first 15 characters will be on one line in the program, and the reminader of the characters will be on the following line. Refer to section 3 in part I for more information about APPEND .
There are several ways to use ALPHA strings in your programs to prompt for data input. Prompts in your programs are a simple way to assure that you input the correct data value. Or you can use prompts to simply display messages.
The easiest way to use prompts is with the PROMPT function. The PROMPT instruction in a program displays the contents of the ALPHA register and stops program execution. Simply key in the ALPHA string as a line in the program and follow it with PROMPT . Execution will halt and the display will show the prompt string.