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1980s Computers Explanation of terms
Notes


The Epson HX-20


HX-20

Manufacturer

Epson (Japan)

Model

HX-20

Date Launched

Late 1982 ?

Price

£411

Microprocessor type

Hitachi HD6301 @ 0.614 MHz
Two processors were used. One controlled the memory and keyboard, the other handled the printer, cassette and sound generator. Presumably this partly made up for the very slow clock speed.

ROM size

32 kilobytes
Expandable to 64 KB

Standard RAM

16 kilobytes

Maximum RAM

32 kilobytes

Keyboard type

Typewriter style with good feel.

Supplied language

Microsoft BASIC with extensions to control the microcassette and other hardware-specific features

Text resolution

20 columns x 4 rows on built-in LCD display.
This acted as a window onto lines of up to 255 characters.
Optionally an external display could be connected.

Graphics resolution

120 x 32 pixels on built-in LCD screen.
128 x 64 pixels in 4 colours or
128 x 96 pixels in 2 colours on external monitor.

Colours available

Monochrome LCD.
If using an external monitor then 2 sets of 4 different colours were available in low resolution:
either (green + yellow + blue + red) or (white + cyan + magenta + orange).
High resolution was black + white.

Example Screenshot

Epson HX-20 LCD screen
This is the HX-20's start-up menu.
The four line screen was a distinct improvement over the single-line display of most pocket computers.

Sound

Single channel through internal speaker

Cassette load speed

1300 baud
The HX-20 was usually supplied with a built-in microcassette, as in the photograph above. This stored 100 kilobytes of data on each cassette and could be completely controlled by software, including reading the tape counter, thus acting as a (slow) disc drive.

Dimensions (mm)
Weight (grams)

290 x 215 x 44
1700

Special features

Fully portable - roughly A4 sized and lightweight.
It was powered by internal batteries and ran for around fifty hours on a charge.
Had a built-in 24 column dot matrix printer using till-roll paper.
Contents of RAM were retained for several weeks when the machine was switched off.

Good points

Compact, neat, all-in-one design, supplied in a rigid plastic protective case.
RS-232C interface and flexible expansion port.

Bad points

Small display size made anything other than simple programs awkward to use.
No parallel interface to connect a full size printer.

How successful?

Popular with those who travelled in their job, including journalists.
Also often interfaced to laboratory equipment for use as a data-logger – I used one in 1988, running a specialist program in an analytical laboratory.

Comments

The Epson HX-20 was one of the first 'laptop' computers, though at that time they were described as 'briefcase' sized.
With a good keyboard for touch typing, full character set and inbuilt cassette storage the HX-20 made a useful portable word processor, the software for which could be stored in the expansion ROM.
The character set included some predefined graphics symbols:


A bar code reader was also available.



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