The +D (or Plus D) was a

floppy disk A floppy disk or floppy diskette (casually referred to as a floppy, or a diskette) is an obsolescent type of disk storage composed of a thin and flexible disk of a magnetic storage medium in a square or nearly square plastic enclosure lined w ...

and

printer Printer may refer to: Technology * Printer (publishing), a person or a company * Printer (computing), a hardware device * Optical printer for motion picture films People * Nariman Printer (fl. c. 1940), Indian journalist and activist * James ...

interface Interface or interfacing may refer to: Academic journals * ''Interface'' (journal), by the Electrochemical Society * ''Interface, Journal of Applied Linguistics'', now merged with ''ITL International Journal of Applied Linguistics'' * '' Inte ...

for the

ZX Spectrum The ZX Spectrum () is an 8-bit computing, 8-bit home computer that was developed by Sinclair Research. It was released in the United Kingdom on 23 April 1982, and became Britain's best-selling microcomputer. Referred to during development as t ...

home computer, developed as a successor to

Miles Gordon Technology {{unreferenced, date=August 2012 Miles Gordon Technology, known as MGT, was a small British company, initially specialising in high-quality add-ons for the ZX Spectrum home computer. It was founded in June 1986 in Cambridge, England by Alan Miles ...

's earlier product, the

DISCiPLE A disciple is a follower and student of a mentor, teacher, or other figure. It can refer to: Religion * Disciple (Christianity), a student of Jesus Christ * Twelve Apostles of Jesus, sometimes called the Twelve Disciples * Seventy disciples in t ...

. It was designed to be smaller, cheaper, simpler and thus more reliable. It discarded a number of the less important features of the earlier product — the

network Network, networking and networked may refer to: Science and technology * Network theory, the study of graphs as a representation of relations between discrete objects * Network science, an academic field that studies complex networks Mathematics ...

and

joystick A joystick, sometimes called a flight stick, is an input device consisting of a stick that pivots on a base and reports its angle or direction to the device it is controlling. A joystick, also known as the control column, is the principal cont ...

ports, the inhibit button and the pass-through connector — and replaced its ancestor's plastic wedge-shaped design which fit under the Spectrum with a simple flat metal slab which protruded from the rear of the computer. It provided only floppy disk and

Centronics Centronics Data Computer Corporation was an American manufacturer of computer printers, now remembered primarily for the parallel interface that bears its name, the Centronics connector. History Foundations Centronics began as a division o ...

parallel interfaces, plus a

non-maskable interrupt In computing, a non-maskable interrupt (NMI) is a hardware interrupt that standard interrupt-masking techniques in the system cannot ignore. It typically occurs to signal attention for non-recoverable hardware errors. Some NMIs may be masked, but ...

button. The +D's casing was simple folded steel, which was not only stronger than before but acted as a heatsink, improving reliability. Apart from the missing ports, though, it was software-compatible with the larger device. The +D's

DOS DOS is shorthand for the MS-DOS and IBM PC DOS family of operating systems. DOS may also refer to: Computing * Data over signalling (DoS), multiplexing data onto a signalling channel * Denial-of-service attack (DoS), an attack on a communicatio ...

was named G+DOS, and was compatible with the DISCiPLE's DOS, ''GDOS''. ''SAM DOS'' for MGT's

SAM Coupé Sam, SAM or variants may refer to: Places * Sam, Benin * Sam, Boulkiemdé, Burkina Faso * Sam, Bourzanga, Burkina Faso * Sam, Kongoussi, Burkina Faso * Sam, Iran * Sam, Teton County, Idaho, United States, a populated place People and fictional ...

was backwards-compatible with GDOS and G+DOS. "The Complete +D Disassembly" by Rudy Biesma documents the "G+DOS system 2a" version. An enhanced version called Beta DOS fixed bugs and added features. In later years a complete new system called UNI-DOS was developed by SD Software for the DISCiPLE and +D interfaces. The popularity of the DISCiPLE led to the formation of a user group and magazine, INDUG, which later became Format Publications. Usergroups like INDUG/Format in the UK or DISCiPLE-Nieuwsbrief in the

Netherlands ) , anthem = ( en, "William of Nassau") , image_map = , map_caption = , subdivision_type = Sovereign state , subdivision_name = Kingdom of the Netherlands , established_title = Before independence , established_date = Spanish Netherl ...

produced enhancements such as extended printer support. The +D design was later licensed by

Datel Datel (previously Datel Electronics) is a United Kingdom, UK-based electronics and video game console, game console peripherals manufacturer. The company is best known for producing a wide range of hardware and peripherals for home computers in t ...

and it continued on sale for some years after MGT's demise. Its design and chips have been released into the public domain and it still remains available commercially or even as a DIY project.

References

External links

How to build a +D for yourself

still offer the +D Disk Interface for sale {{DEFAULTSORT:Plus D ZX Spectrum