Hewlett-Packard's New Personal Computer
The HP-85

Article originally appeared in BYTE Magazine, March 1980.
Reprinted with permission, courtesy of Byte.com

Christoher P. Morgan
Editor in Chief

Photos by Ed Crabtree

A question often heard in personal computer circles is, "When, is Hewlett-Packard going to bring a personal computer?" The question has been answered, and the new HP-85 computer is quite a system.

Hewlett-Packard (HP) has long been a respected manufacturer of minicomputers, desktop calculators. and hand-held calculators; the high quality of their electronic test equipment is well known to the engineering community; Hewlett-Packard also has the reputation for being a careful, conservative company, and the HP-85 is, not surprisingly, a logical outgrowth of their desktop and hand-held calculators.

We recently had the opportunity to audition the HP-85. Our preliminary findings are listed below.

System Features

The basic HP-85, shown in photo 1, costs $3250 and consists of a microcomputer with a custom 8-bit processor and several other custom integrated circuits, data cartridge drive for DC-l00 tape cartridges, a high-resolution video display with a 5-inch screen (measured diagonally) with resolution of 256 by 192 dots (individually addressable) for graphics, 16 lines by 32 characters of text, keyboard, and thermal printer. The unit comes with 16 K bytes of programmable memory (14,500 of which are available to the user) expandable to 32 K bytes, and 32 K bytes of read-only memory. The latter contains the operating system and the Enhanced BASIC package.

Photo 1: Hewlett-Packard's new entry into the personal computer market: the HP-85. The $3250 unit features a 5-inch video display, data cartridge, keyboard with user programmable keys, and thermal printer. The HP-85 also offers interesting graphics capabilities. Every point on the 256 by 192 dot array can be individually addressed by the programmer. The built-in thermal printer can make a copy of any graphic design on the screen or any alphanumeric data. Sophisticated features included in this unit are a hardware and software self-test key; four levels of security protection for files on data cartridges; plug-in memory expansion to the basic package of 16 K bytes of programmable memory and 32 K bytes of read-only memory; ANSI standard Enhanced BASIC with the ability to chain programs together; and line editing.

Data Cartridges

One of the main differences between the HP-85 and most other small systems on the market is its use of data cartridges for reading and writing programs and data. This is not surprising, since the company expects to sell the unit in large quantities to professionals, and the data cartridge is one of the most reliable forms of mass storage available today. The cartridge-drive slot is located on the front of the machine (see photo 2).

Photo 2: Inside the HP-85, showing the 5-inch video display cathode-ray tube, thermal printer, and data cartridge drive. The processor board is located under the keyboard (see photo 4). Note the set of user-definable keys in the upper left corner of the keyboard. Labels for these keys are displayed at the bottom of the video screen.

Each cartridge can hold 780 program records consisting of 192 K bytes each, or 850 data records of 210 K bytes. There can be a maximum of forty-two named files per cartridge. Cartridge rewind time is 29 seconds; search speed is 152 cm (60 inches) per second; data transfer speed is 25.4 cm (10 inches) per second; and tape length is 43 meters (141 feet). With the data cartridge system the user can create data files, input arrays into the computer with a single program statement, store an "autostart" program that is automatically loaded and executed at power-on, and secure programs from unauthorized access.


The keyboard is divided by function: the typewriter keyboard for entering alphanumeric data, the numeric pad for entering numeric information, and eight user-definable keys. (These keys are located directly under the video screen. Labels for the keys can be entered by the user and will appear at the bottom of the screen). Display, editing, and system-control keys permit the user to control the video display. The keyboard is hinged and can be easily swung out of the way after the cover is removed to service the processor board (see photo 3).

Photo 3: Internal view of the HP-85 showing the processor board under the hinged keyboard. The 8-bit processor is a custom Hewlett-Packard design, as are most of the integrated circuits in the computer.

Video Display

One of the HP-85's strong points is its graphics and alphanumeric display capability. Sixteen lines of text can be displayed at a time on the screen, but a buffer holds up to sixty-four lines, so the user can back up and see a part of a listing that has scrolled off the screen - a decided convenience in writing or debugging programs. If you come to the end of the sixty-four-line section in the buffer, the display wraps around to the beginning again. Characters are formed in a 5 by 7 dot matrix.

In the graphics mode, the display consists of a 256 (wide) by 192 (high) dot field, giving a total of 49,152 individual dots available for high-resolution plotting. The HP-85 also stores the last alphanumeric display and the last graphics display in separate buffers so the user can switch more freely from one mode to the other without losing data.

Readers familiar with the company's desktop calculators will be immediately at home with the HP-85's graphics-handling routines. There are sixteen graphics commands for setting up graphs, locating the origin, and scaling and labeling the axes quickly.

Anything that appears on the screen can be printed on the thermal printer by simply pressing the GRAPH and COPY keys in that order. You may also enter commands from the keyboard while in graphics mode. Inverse video is also available, as well as a BPLOT routine for user-defined graphics.

The alphanumeric characters are on the small side compared to the average personal computer display because of the screen size. However, they are quite readable - not unlike the IBM 5100 display. Screen editing is convenient. There are five cursor-control keys, plus keys for clearing the screen, a line, or a single character. The ability to edit within a program line is a great time saver.


The HP-85 offers unprecedented versatility when it comes to securing data and programs. The SECURE command is used to prevent specific program files from being listed, edited, or stored; to prevent any file's name from appearing in the directory listing; and to protect the user from writing over a file. The UNSECURE command removes security on secured programs or data files. The file name to be secured must already appear in the directory (ie: it must already exist on tape).

The file name may be any string of characters except the null string. The system takes the first two characters of the string and stores them as the security code. There are four levels of security.

At level 0, the program may not be listed or edited. Level 1 further prevents the program from being duplicated. At level 2, the program may also not be overwritten. Level 3 removes the name of the file from the catalog and replaces it with blank.


The thermal printer operates in both alphanumeric and graphics modes. In the alphanumeric mode, it can print the full128-character ASCII character set, which includes upper-case and lowercase letters, numerals, and special symbols. The full character set can be underlined. Printer speed is 2 lines per second.

Enhanced BASIC

The HP-85's Enhanced BASIC interpreter meets and exceeds the most recent ANSI standard. Its features include: 12-digit accuracy and exponents up to +/- 499 for calculations; extremely versatile string handling capability (a string in the Enhanced BASIC can theoretically be up to 32 K bytes long) compared with string handling on other microcomputers; 42 predefined functions for formatted output; the ability to chain BASIC programs together; multistatement lines; a programmable sound generator that can play single-voice lines of melody through the built-in speaker or make audible beeps at predetermined times during the execution of a program; and calculator capability. For debugging, the user can single-step through BASIC programs, branch ON ERROR, or have the program provide a default value with DEFAULT ON to enable a program to continue executing. In particular, the formatted-output capability is useful for generating headings, columns, and spaces for program output.


A unique feature of the HP-85 is the built-in self-test routine. When the TEST key is pressed, the computer runs through an electronic check of all internal components - a feature common to many Hewlett-Packard electronic instruments. If everything checks out correctly, a particular set of characters is displayed on the screen. (The graphics display will be cleared, but programs and variables in memory will remain intact.) If the system is not operating correctly, the system displays "Error 23 SELF TEST."


Photo 4 shows the back of the HP-85 and the four input/output (I/O) ports. Additional memory can be added via the ports. The company will be introducing a variety of peripherals for the unit, including dual 5-inch floppy-disk drives, external printers, plotters, and so on. An extra 16 K bytes of memory costs $395.

Photo 4: Rear view, showing the I/O ports and their removable covers.


Software currently available on data cartridges for the HP-85 includes BASIC training, general statistics, mathematics, electrical engineering, finance, linear programming, and regression analysis. Each package costs $95. More packages are under development. BASIC programs developed for Hewlett-Packard's desktop computers can be adapted for use on the HP-85, as can most programs written in ANSI BASIC. The unit also comes with a well-written, 350-page owner's manual and a standard application software package. Hewlett-Packard is quoting immediate delivery on the HP-85.


We were impressed with the performance of the HP-85 computer. The graphics alone make this an attractive, albeit not inexpensive, alternate to existing small systems on the market. And many of its features are unique. Although Hewlett-Packard is pinning its hopes on heavy sales to the professional marketplace, it is our guess that many personal computer experimenters and hackers will want this machine.

In future issues of BYTE we will evaluate the HP-85 in greater depth.

For further information about the HP-85, contact: Inquiries Manager, Hewlett-Packard Co, 1507 Page Mill Rd, Palo Alto CA 94303.

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