HP 9836A

HP 9800 series
Company type	Product line
Industry	Computer hardware
Predecessor	HP 9100 calculator
Founder	Hewlett-Packard
Fate	Discontinued and replaced by HP Series 80 and later personal computers
Successor	HP Series 80
Headquarters	Loveland and Fort Collins, Colorado, United States
Area served	Worldwide
Products	Programmable calculators and desktop computers (e.g., HP 9810A, HP 9820A, HP 9830A, HP 9825, HP 9835, HP 9845)
Owner	Hewlett-Packard
Parent	Hewlett-Packard

Adapted from the English Wikipedia article HP 9836A, available under CC BY-SA 4.0Updated 8 August 2025

The HP 9800 series, frequently referred to as the "98 line," comprises a range of programmable calculators and subsequent desktop computers created by Hewlett-Packard. This series followed the HP 9100 calculator and included models like the HP 9830 and its successors, which were genuine computers equipped with a robust BASIC interpreter.

Second generation

Notable models within this generation include:

HP 9810A (1971): A keystroke-programmable device featuring magnetic card storage and an LED display.
HP 9820A (1972): HP's initial model to support algebraic input, utilizing a high-level language later identified as high performance language (HPL), which was simpler than BASIC.
HP 9821A: Essentially a variant of the 9820A that replaced magnetic cards with a software-controlled Compact Cassette tape drive, facilitating file-based saving and loading.
HP 9830A (1972): The flagship unit equipped with a BASIC interpreter stored in read-only memory (ROM); HP promoted it as a "calculator."

All systems in the 98x0 series and the 9821 shared standardized input/output interfaces. An optional thermal line printer capable of printing 400 lines per minute on 80 columns was designed to be mounted atop the 9820 and 9830 units, enhancing their functionality for business applications.

Third generation

Building upon the achievements of the HP 9830, the third generation introduced faster processing capabilities and included:

HP 9805A, launched in 1973 as an affordable programmable calculator featuring interchangeable personality modules.
HP 9815A/S, released in 1975 as HP’s third-generation high-end RPN desktop computer; it was more compact and lightweight than its predecessor and incorporated a single-line display alongside a tape drive replacing earlier card drives.
HP 9825A/B, available from 1976 until its discontinuation in 1983, supporting programming in HPL, equipped with a single-line alphanumeric display and an optional thermal printer.
HP 9831, a variant of the HP 9825 that ran BASIC instead of HPL.
HP 9835, featuring BASIC and serving as the basis for the HP 250 business computer family; offered in two versions—Model A with CRT display and Model B with a single-line display.
HP 9845, initially introduced as monochrome models (9845A/S), later upgraded to high-performance monochrome versions (9845B/T), and eventually color models (9845C/T); these included tape drives and an optional integrated 80-column thermal printer beneath the screen.

With the exception of the 9805, these devices utilized DC200 cartridge tapes rather than cassettes. The HP 9825, 9831, 9835, and 9845 shared common I/O interfaces, whereas the HP 9815 employed a distinct interface.

An ancestor of modern personal computers

Originating from HP’s Loveland Calculator Products Division and later developed by the Fort Collins Desktop Computer Division, the HP 9800 series was initially marketed under the designation "Calculators" to simplify purchasing procedures. This lineup paved the way for the HP Series 80 family—including models like the HP 85 and HP 87—which were more compact BASIC computers featuring CRT displays developed by HP’s Advanced Products Division based in Corvallis.

During the late 1970s through early 1980s, these desktop computers competed against contemporaries such as the Tektronix 4051, IBM 5100, and Wang 2200 before being gradually replaced by personal computers like those from Apple and IBM.

Applications of the HP 9830

The HP 9830 found use in aerospace companies such as Boeing and in educational settings including schools in Arlington, Virginia, and Renton, Washington, where pencil mark-sense cards were employed to facilitate classroom activities. During the early 1970s, National Real Estate Exchange, Inc. utilized an HP 9830 system equipped with an integrated hard disk to create pioneering real estate software.

The U.S. Coast Guard deployed HP9825A units for experimental teletype message forwarding and managing LORAN radionavigation systems. Furthermore, HP9825 computers combined with Oscor software were used for scoring at one-design yacht regattas held at distant venues like the 1976 World Fireball Championships in Nova Scotia and the World Windsurfing Championships in Cancún and the Bahamas. The portability of the HP9825 made it a preferred choice over unreliable telephone-based time-sharing systems in these remote locations.

Overview of the HP 9830

The architecture of the 9830 series closely mirrored that of the HP 1000/2100 minicomputers, featuring 16-bit memory addressing and AX/BX general-purpose registers, operating at speeds comparable to early IBM PC models. These machines were capable of producing intricate three-dimensional plots, including functions like a 3D SIN(X)/X graph with hidden line elimination—a significant technological feat during that era.

Programs resided in ROM, necessitating a modified subroutine call technique that employed a dedicated stack register for return addresses, thus supporting recursive function calls. Certain variants, such as the 9835B model, incorporated a 32-character single-line uppercase LED display. This display acted as a one-line viewport into a comprehensive screen editor featuring cursor movement and line navigation—predating widespread adoption of screen editors in the 1980s. Upon power-up, the system was immediately ready for mathematical input (for example, PRINT 2 + 3), removing the need for login procedures or large computer room infrastructure.

Data storage was handled by a computer-controlled cassette drive with optical sensors detecting tape ends; files could be accessed randomly by their assigned numbers. Additionally, hard drives could be interfaced with the system. The included line thermal printer produced output one horizontal dot line at a time, achieving page printing speeds faster than subsequent dot matrix printers and comparable to early inkjet models. HP extensively incorporated thermal printing technology into later plotting devices and terminal products.

Programming

Although built on minicomputer processors, the system’s software was entirely redesigned to include an operating system and programming language embedded within ROM. The BASIC language offered was reminiscent of engineering-focused FORTRAN, yet simpler and interpreted rather than compiled. Interactive editing was facilitated by arrow keys that allowed scrolling through lines and inserting or deleting characters—capabilities rare before late-1970s screen editors. Developers could execute programs step-by-step while monitoring variable values.

Two rows of user-programmable function keys equipped with paper labels represented some of the earliest implementations of general-purpose function keys, influencing subsequent designs of screen labeled function keys on HP and IBM terminals—features now common on calculators, banking terminals, and fuel dispensers.

Programming primarily utilized BASIC but could be extended via ROM cartridges offering additional functionality such as graphics plotting, matrix operations, and string manipulation—akin to expansion cartridges used in video game consoles. The Plotter ROM streamlined chart creation by allowing coordinates to be specified in user or world units rather than device-specific measurements. These commands laid the groundwork for HP's device-independent AGL graphics language standard employed on HP 1000 minicomputers and HP 2647 graphics terminals. <syntaxhighlight lang="basic">

10 REMARK DRAW A PARABOLA
20 SCALE -1.0, 1.0, -1.0, 1.0
30 FOR X = -1.0 TO 1.0 STEP 0.10
40 PLOT X, X*X
50 NEXT X
60 END

</syntaxhighlight> A bootable development environment based on UCSD Pascal was also offered for programming on the HP 9800 series systems.

Overview of HPL Language

Instead of using variable names such as A1 or J2, HPL employed numbered registers ranging from r1 up to r199999.

Below is a sample HPL program for the HP 9825 that outputs a sequence of prime numbers:

0: fxd 0  
1: prt 2  
2: 1→P  
3: for C=2 to 1000000  
4: P+2→P  
5: for N=3 to P/3  
6: if int(P/N)*N = P; gto 3  
7: next N  
8: prt P  
9: next C

A notable characteristic was the use of the right-pointing arrow (→), referred to as the gazinta ("goes into"), which was utilized in assignment statements like 1→P.

Additional BASIC-Based Machines

HP’s Data Terminals Division created the HP 2647a, a terminal programmable in BASIC that incorporated AGL—HP’s standardized command set for the HP 9830 plotter. The BASIC interpreter on the HP 2647 was essentially Microsoft BASIC augmented with HP-specific plotting features, representing one of Microsoft’s earliest significant partnerships with a major computer manufacturer.

HP also produced handheld pocket devices such as the HP-75, although these models saw limited commercial traction. The HP 9835 acted as a cornerstone for business-oriented computing solutions, eventually leading to the development of the HP 250 platform.

In 1979, HP launched the HP 85, marking the debut of the Series 80 family—cost-effective personal desktop scientific computers equipped with a robust BASIC interpreter tailored for individual users and professionals.

This division later transitioned into manufacturing UNIX-based HP 9000 workstations and acquired Apollo Computer. The evolution of HP BASIC continued into Rocky Mountain BASIC designed for these workstations, which still supports legacy software environments.

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