Terminated: 1985
The HP 41C series has three models, here in chronological order:
The HP 41C is, as far as I am aware, the first handheld programmable calculator with an alphanumeric display. It uses RPN with a four-level stack. It was before dot-matrix LCD’s existed, and it uses a clever display using 14 segments.
It has constant memory and has four extension slots. One of its extensions is a card reader (see the HP 41CV page on this museum for an image). The case is wonderful and, well, only HP could build them like this. Everything about its housing is beautiful. The keys have an excellent feel, the wedge form is well thought out. For me personally this is still the best looking calculator ever.
It runs on four N-type batteries. Be sure to use 1.5V N-type batteries for using their 12V lookalikes will kill the calculator! A capacitor holds the calculator’s power for around 30 to 60 seconds when replacing batteries. Be sure to switch the calculator off first.
A very nice touch is that accidentally pressed keys can be undone by simply holding the key down a bit longer. First the name of the pressed key is shown. When you hold it down longer the display will show NULL and no action is performed. This holds even for the clear key ←! A very nice and a very user friendly addition.
Use the CATALOG function ( ENTER↑ ) to view all available commands. CATALOG 3 shows all built-in commands. Slow the listing down by pressing a key, pause it by pressing R/S. Use CATALOG 1 to list all user defined programs. CATALOG 2 will list commands defined by installed modules and extensions.
Not all built-in functions are available under keys. That is where the XEQ (execute) key is for. To calculate the factorial of 69 for instance (which is really fast on this machine) enter 6 9 XEQ ALPHA F A C T ALPHA.
User defined programs can be called using the XEQ key as well. Set the angle mode to RADians for instance by entering XEQ ALPHA R A D ALPHA.
The calculator has many more functions than are available using its keys. To make things easier this calculator has a special USER mode. The USER key switches between modes. Almost any key can be assigned another function in USER mode. Ones own labeled programs can be assigned to keys as well (as long as they use non-local labels. Labels A-J and a-e are reserved for usage locally in programs).
To assign a new function to a key use ASN ALPHA [the name of the function or the name of a label] ALPHA [the key]. This way many useful functions as well as ones own programs are available when switching the calculator to USER mode by pressing the USER key.
To help the user, memory registers 01 to 10 are easily accessible by using the two top lines of keys. For instance, store something in memory register 05 by typing STO LN (LN is the fifth key).
Memories can hold numerical values but can also hold 5 characters of alphanumeric data.
A powerful function is the ability to use operands when interacting with memory. For instance press 4 2 STO × 0 1 to multiply memory location 01 by 42.
The ten top row keys can be used for quickly selecting positions 1 to 10 in other places as well, for instance with specifying a LBL (label), with GTO (goto), and when specifying flags using SF (set flag), CF (clear flag) and FS? (is a flag set?).
To help with programming and flow control the HP 41C has flags. They can be either YES or NO. 32 flags are available for the user, flags 33 till 55 are system flags. One notable one is the flag to change the decimal separator to the comma, simply use CF 28 to switch to the comma as a decimal separator. Flag 29 enables or disables the display of thousand separators.
The display has indicators for flags the first four flags (01 - 04).
Its programming capabilities are quite powerful. Using flag 11 auto execution of a program when the calculator is switched on, can be set. Auto-power-off can be disabled.
It can store multiple user defined programs. All programs should start with a named label and end with an END instruction which can be entered using the GTO command ( RCL ). To insert the END function use GTO . ..
Another really powerful feature is its ability to do indirect operations. Any function that requires an index can use this feature. For instance, to recall a memory location which index is stored in register 01 use RCL 0 1. This can be used for all functions requiring a numerical index.
The HP 41C has a build-in piezoelectric crystal to produce sound. use the BEEP command to sound its build-in tri-tone sound. Use TONE followed by a single digit (or an indirect value using the key!) to specify a pitch of your own.
Reset the calculator (clearing its memory, which is sometimes necessary when taking the batteries out just a bit to long) by switching the calculator on while holding down and then releasing the ← key.
The HP 41C series calculators have had a very long lifetime. The range of peripherals is amazing.
For more information on this beauty please refer to the better sources, like The Museum of HP Calculators (link validated 2024-11-14).