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
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
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
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
shows tape contents of drive assembly 1.
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 .
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
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.
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.