The Epson PX-4 (HC-40 or HX-40) is a portable CP/M based computer introduced in 1985. The screen was 40×8 characters physical, but 80×25 or 40×50 virtual, making it almost compatible with the

Epson PX-8 Geneva The Epson PX-8 a.k.a. Geneva was a small laptop computer made by the Epson Corporation in the mid-1980s. It had a Z80 compatible microprocessor, and ran a customized version of the CP/M-80 operating system as well as various applications from a ...

. It could be operated from a Nickel-Cadium battery pack (Epson RB 105), 4xAA batteries, or a 6V 600mA DC power supply. It was targeted as successor of the

Epson HX-20 The Epson HX-20 (also known as the HC-20) was the first "true" laptop computer.Michael R. Peres''The Focal Encyclopedia of Photography'', page 306 Taylor & Francis It was invented in July 1980 by Yukio Yokozawa, who worked for Suwa Seikosha, a bra ...

portable, which was very popular with field engineers. Another feature of the PX-4 was its high modularity. Inheriting the ROM capsules from the

, it added a cartridge bay (similar but incompatible with the

), for which Epson offered several printers, micro-cassette drive, modem, EPROM writer, DMM (Digital Multimeter Module), RAM and ROM cartridges.PX-4 OPERATING MANUAL Third parties could make custom cartridges. The modem, EPROM writer and DMM needed user programs. The system allowed for BIOS extensions (User BIOS). Other features were the Serial ''and'' RS232 port, barcode reader interface like with the

. New were a cassette port and

parallel printer port In computing, a parallel port is a type of interface found on early computers (personal and otherwise) for connecting peripherals. The name refers to the way the data is sent; parallel ports send multiple bits of data at once ( paralle ...

. The keyboard was also easily replaceable, allowing country specific layouts but also custom layouts, like the 'item keyboard' turning the PX-4 into a cash register. This trend was taken further by the

Epson PX-16 Seiko Epson Corporation, or simply known as Epson, is a Japanese multinational electronics company and one of the world's largest manufacturers of computer printers and information- and imaging-related equipment. Headquartered in Suwa, Nagano, ...

for which even 'item keyboards' with touch screens were available. Internal RAM was 64K, of which a part could be reserved as RAM disk. An External RAM disk could be attached, creating a 120K RAM disk, leaving internal RAM as user BIOS and workspace. The PX-4+ was an improved version which had the External RAM disk integrated (HX-45 in the USA, HC-45 in Japan).

References

;Literature * ''PX-4 / HX-40 Operating System Reference Manual'', EPSON, 1985. Y20699101600 * ''PX-4 DISK UTILITIES OPERATING MANUAL'', EPSON, 1984. H8592003-0 / Y322990003 * ''PX-4 BASIC REFERENCE MANUAL'',EPSON, 1985. Y200599100601 * ''PX-4 OPERATING MANUAL'' EPSON 1985. H8592005-1 / Y205991005

External links

PX-4 info, documentation and software
{{microcompu-stub PX-4