Hewlett-Packard HP-9825A

The HP 9825A (AKA the 9800 series model 25) was a powerful fully algebraic desktop calculator. It replaced the HP 9820A and made a number of improvements including a full QWERTY keyboard (plus special function keys), a 32 (instead of 16) character display, and major extensions to the programming language. This new extended language was called HPL.

Introduced 1976

Live Keyboard
A new feature on this calculator was its "live keyboard". On most calculators, the keyboard was (and still is) disabled during program operation. The live keyboard allowed the user to examine and change variables, perform calculations and list programs while a program was running. The user could even execute subprograms within the running program.

Tape Drive
The calculator included a tape drive capable of holding 250K bytes with a 2.7KBps transfer rate and an average access time of 6 seconds. An autostart feature allowed the calculator to load a program from tape whenever it was turned on. Another interesting feature of the tape drive was its ability to save the entire state of the machine. If the machine was in the middle of a lengthy program, the user could save the entire state to tape, run some other program and then resume the lengthy program from the saved tape image. The combination of the "live keyboard" and the ability to suspend any program to run another gave this calculator a new level of interactivity.

HPL Programming
The computer used a "new" language with the new name HPL. However, users of the HP 9820A would have found it quite familiar. For example, keywords like prt (print) and gto (go to) were retained and gto could still jump to line addresses or labels. If statements continued to evaluate an expression and execute the next statement on the line if the expression was true. Expressions were still fully algebraic including implied multiplication (ie 4AB meant 4*A*B.) The numbered registers of the HP 9820A were gone with 26 single letter variables and 26 arrays in their place. (Of course, an HP 9820A user could feel more at home by declaring an array R[0:172] to simulate the old registers - see arrays below.)

Our seial numbers are:

Further details of the HP 9825A can be found at
http://www.hpmuseum.org/hp9825.htm and

Our two units werer very kindly donated by QinetiQ from Great Malvern which was kindly arranged for us by Michael Hamer of QinnetiQ.

Manufacturer: Hewlett Packard
Date: 1976

Other Systems Related To Hewlett-Packard HP-9825A:

Item Manufacturer Date
Hewlett-Packard HP-71B Programmable Calculator Hewlett Packard Unknown
Hewlett-Packard HP-34C Programmable Scientific Calculator Hewlett Packard Unknown
Hewlett-Packard HP-11C Hewlett Packard Unknown
Hewlett Packard HP-35 Hewlett Packard 1972
Hewlett-Packard HP-9825B Hewlett Packard 1976

This exhibit has a reference ID of CH4928. Please quote this reference ID in any communication with the Centre for Computing History.


Hewlett-Packard HP-9825A

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