Unlike the 9810, 9820 and 9830 series, the 9825, 9835 and 9845 were not all released at the same time. Also unlike the earlier series, the 98x5 series shared many common interfaces and peripherals. The 98x5 series computers all use the new tape drive that was developed to use the 3M DC-100 tapes. HP sold these tapes (picture) under part number 9162-0061 These tapes had a metal back plate for additional stiffness and could not be driven via the capstans. Instead there was a drive wheel/pulley on the edge of the cassette that engaged with a rubber drive wheel in the drive. The drive wheel/pulley in turn drove rubber belt (drawing) that drove the tape capstans.
The HP 9825 was introduced in the June 1976 issue of the HP Journal (picture) and was probably the most widely produced of all of HP's desktop calculators. It's development code name was "Keeper" because it was originally going to have a "key per" function like its predecessor, the 9820/21. The low profile keyboard was given the development code name "Cricket" because of the sound that some of the keys made! The 9825 was a third generation machine and featured NMOS hybrid technology, two-level priority interrupt, a live keyboard and direct memory access with input speeds of up to 400,000 16 bit words per second. The live keyboard feature allowed changing variables or program statements while the program is running, or to list the program while it is running. Optional character sets include German, French, Spanish and Katakana. Other features included a high speed bi-directional tape drive with a capacity of 250k bytes, the ability to handle multi-dimensional arrays and an extended number range (+/- 10 ^ 511 to +/- 10 ^ -511). It also featured four ROM slots in the front and three I/O slots in the rear of the case. The 9825 used the formula oriented HPL language and was capable with the HPL used by the HP 9820 and 9821. HPL was HP's version of the then widely popular APL language. HPL allowed subroutine nesting, flags and multi-dimensional arrays of up to the size of the system memory. The 9825 used a 32 character LED display in which each character was made up of a 5 x 7 matrix of individual LEDs. This allowed the machine to displays numeric and both upper and lower case letters. Even thought the display only displayed 32 characters, up to 80 characters could be input at a time. After the 67th character was input, the machine would beep to indicate that it was nearly full. The 9825 allows multiple entries per line. Each entry could be separated by semicolons. The 9825 allowed simple variables but they could only be one character long and were limited to the uppercase letter therefore only 26 simple variables could be used. However it also allowed the use of numbered registers for variable storage. The use of registers also allowed indirect storage of values. For example "20 --> r r10" would store the value 20 in the register who's number was in register 10. The optional Strings ROM also permitted the use of string variables. The 9825 also used the same 16 character printer that was used in the HP9815.
The 9825 was produced in at least three models, the "A", "B" and "T" models. The 9825 technical Specifications dated May 1980 also list a "S" model but I have never seen one and have not found one listed in any of the HP catalogs. The original A version was easily recognized by it use of low profile keys and by the pull out drawer in the right hand side (picture). The ROM drawer contained the Operating System ROMs. The B version had many enhancements including the use of full height keys, 23 K of read/write memory plus built-in Strings, Advanced Programming, General I/O, Extended I/O and Plotter ROMs. HP also dropped the pull out OS ROM drawer and built the OS ROMs into the machine in the B model. The T version had all the enhancements of the B model but also included the then new Systems Programming ROM and 61k bytes of read/write memory.
The designer of the 9825 Cricket keyboard designer was Ron Lingeman, who later started Otrona, an early portable CP/M and computer vendor in Boulder, Colorado.
The model markings on the 9825s can be very confusing. It's common for them to have one model marked on the outside but to have another model number listed under the paper cover. I have one that's marked "9825A" on the back label but marked "9825B" next to the display and "9825T" under the paper cover! I have never seen one marked "9825T" on the outside. They are almost always marked 9825B on the outside but under the paper cover they are usually marked "9825T" "Installed devices: 9872A Plotter, General I/O, Extended I/O, Advanced Programming, String, System Programming , Total Memory 61670 Bytes". Strangely, I also have 9825B that says exactly the same thing except that it says "9825B" instead of "9825T" under the paper cover. I'm guessing that it was a prototype for the "T" model. That machine also has a large warning label on outside top warning the user not to install any ROMs other than the 98211 Matrix ROM or the 98217A Flexible Disk Drive ROM. It says that installing any plug-in ROM that is already built into the calculator may damage the machine. I have never seen this warning on ANY other HP machine. The "B" and "T" models weren't the only ones to get labels under the paper cover. I also have a 9825A with the chicklet keys that says "9825A" "Installed devices: 9872A Plotter, General I/O, Extended I/O, String, Advanced Programming, Matrix, Opt 001 15036 bytes, Opt 002 23228 bytes".
One of the more interesting ROMs for the HP 9825A was the HP 98224A Systems Programming ROM. Originally, this ROM was called a "COM ROM" and was conceived of as a support ROM for the more advanced functions of the 98036A, like full-duplex serial I/O and better access to the control and status registers, that were not supported by the original I/O ROMs. The "COM ROM" was intended to replace the HP 11205, HP 11206 and HP 11284 ROMs that were used in the HP 9830 for communications. When used with the HP 98036 RS-232 interface, it allowed the 9825 to be used as a computer terminal and also allowed the 9825 to use a remote keyboard. However as it's development continued more features not directly related to communications were added so it was eventually named a Systems Programming ROM. It proved so useful that the ROM was built into later 9825 T. One of it's more interesting features was the ability of reading in ASCII from anywhere (serial, paper tape, etc.) and converting these to the internal, tokenized program format used by the 9825. They did this by hooking into the same routines used to store a line of code into the program from the keyboard, hence the command syntax "Store A$." Briefly, they took the ASCII, stored it into the 9825's keyboard buffer, and "virtually" smacked the "store" key on the keyboard. They also added the ability to suppress error checking so the results could be "interesting" if the operator made a mistake! Because the 9825 allows you to store a line into a running program from the keyboard, this feature allowed you to write self-modifying programs. Everyone was very nervous about creating a way to write self-modifying code, hence the cartoon. showing COM ROM blowing a 9825 apart was circuited within HP. If you look closely, the 9825 display is saying "Jeeez." Here is a picture of THE original Systems programming ROM. Note, the red racing stripes on it! Enough said!
The HP 9825 was dropped from the HP catalog after 1983. HP stated that the replacement for the 9825 was the HP 9826 (AKA 9000 226, development name "Chipmunk") running HPL. But it should be noted that 9816 and 9836A were compatible and could also run HPL. The HPL for the 9000 200 series computers was compatible with the 9825 HPL and HP even referred to the HP 9825 manual for a language reference. The 9000 200 series HPL was available as a disk based system or on plug in ROM cards.
Opt 001 15036 Bytes
Opt 002 23228 Bytes
Opt 003 32K Bytes
HP 98210A String - Advanced Programming
HP 98211A Matrix
HP 98213A General I/O - Extended I/O
HP 98214A 9862A Plotter- General I/O - Extended I/O
HP 98216A Plotter- General I/O - Extended I/O (some are marked
"9872A Plotter- General I/O - Extended I/O"
HP 98217A 9885M Flexible Disk Drive ROM
HP 98224A Systems Programming ROM
HP 98228A Disk ROM {supports both 9885 and 9895 drives}
(1977) 9825A = $ 5,900
(1979) 9825A = $ 5,900
(1981) 9825B = $ 7,700
9825T = $ 8,200
(1983) 9825B = $ 8,100
9825T = $ 8,600
Base 15 x 21 x 5 inches 26 pounds
