ZX Printer

The ZX Printer, launched in November 1981 at a price of £49.95, was Sinclair's typically non-standard answer to the prayers of ZX81 (and, later, Spectrum) owners who wanted a printer for their computer. In those days, a good-quality printer could cost upwards of £250 or more - in the ZX81's case, this would have been several times the cost of the computer itself. Although it was possible to connect a parallel-port printer to the ZX81 or Spectrum via third-party interfaces (or Sinclair's own Interface 1, in the case of the Spectrum), there was clearly a market for a budget alternative. As such, the ZX Printer was a popular product and sold tens of thousands of units.

The design of the ZX Printer was heavily influenced by similar devices available at the time in the United States. It was never intended for word processing purposes, instead being aimed at users who wanted to obtain program listings for reference purposes. The printer used black paper coated with aluminium and printed 32 characters to a line. Two styli were mounted on a belt which moved across the paper. An electric charge was passed through the styli, burning away the aluminium coating to reveal the black paper underneath in the shape of the appropriate character. This ingenious approach gave clear if slightly ragged results, but unfortunately the machine itself was not very robust - the print quality rapidly deteriorated with use. For that reason it is uncommon today to find a well-functioning ZX Printer.


The Microdrive for the ZX Spectrum is, as unusual with Sinclair used, relatively. Differently than other manufacturers Sinclair set on continuous cartridges instead of on disks, which quite low-priced, but an isolated solution was. The procurement of suitable continuous cartridges was already at that time rather with difficulty, today gets one it as well as no more (on the other hand are directly easy 3"-Disketten to keep...).

However, the Microdrive fits very well the Spectrum. It is very small (50 x 90 x 86 mm) and co-ordinated from the Design perfectly with the computer. The drive assembly cannot be attached however directly at the Speccy, but one needs still the interface 1 (additionally for the Microdrive connection also still another RS232-Schnittstelle and a network connection contains).

Microdrive Cartridge

The cartridges for the Microdrive are like the equipment genuine Winzlinge: they are only 44 x 35 x 8 mm "largely", which corresponds to a matchbox in approximately the size. In it are contained approx. 5 meters volume, which can be rewound in 7 seconds once - from it a volume speed of approx. 71 cm/seconds results!

Before first using a Microdrive cartridge must be formatted only once, as it is usual with disks also. This is done via the instruction FORMAT "m";1;"Kassettenname" , whereby for the cartridge name a stringer may be used by up to 10 indications. Thereupon the Spectrum begins with formatting, which is also indicated by flashing the edge of screen. After approximately formatting is terminated 30 seconds, the computer announces themselves then again and indicates the names of the cartridge as well as the storage location available on it.

The storage location the available can vary by the way strongly, since when formatting illegible or recordable places are not marked as unbenutzbar. Maximally 96 KByte per volume are attainable, correspond twice to complete memory contents of the Spectrum 48K.

Here still a few other important MD OS instructions:

SAVE * "m";1;"Dateiname"
the program under the indicated file name on drive assembly stores 1.

LOAD * "m";1;"Dateiname"
VERIFY * "m";1;"Dateiname"
MERGE * "m";1;"Dateiname"
the indicated program loads 1 from drive assembly (and/or it compares with the program in the memory and/or adds the program of the drive assembly).

shows tape contents of drive assembly 1.

ERASE "m";1;"Dateiname"
the indicated program of the volume deletes.

OPEN # n;"m";1;"Dateiname "
the indicated file under the file number opens n on volume. If the file does not exist yet, it can with PRINT # n or CUNNING # n to be described, anderfalls with INPUT # n or INKEY$ # n be selected. The file is closed then finally with CLOSE # n;"m";1 .

Interface 1

This was the General purpose interface for the Spectrum, it had communications ports, and a port for the ZX MicroDrives.
The interface itself contained an 8K ROM which had all the new software to control the extra hardware, a Ferranti ULA, and a few discrete components

The new ROM also allowed the user to add their own BASIC commands the standard set by means of an error vector, which meant that a programmer could set an address of a routine which would be called if the BASIC interpreter encountered a command it didn't understand, the routine could then check to see if it knew about the mysterious command and perform an action on it.

Interface 2

This new and improved interface was Sinclair's admittance that his machine was being used for games. It effectively turned the Spectrum into a games console, with the inclusion of a ROM cartridge slot and two joystick ports.
The games cartridges were basically 16k replacement ROMS for the machine's internal one, this was done by simply grounding the !ROMCS line and mapping the new ROM into 0x0000 - 0x3fff.

This is all well and good but of course the game can't access the internal ROM routines, and so has to have it's own Interupt routines, etc.

The Interface II also had a through connector that was only big enough for the ZX Printer and was even labelled so.

©2002 ZeDeX82