Developer: Science of Cambridge (renamed to Sinclair Computers Ltd in November 1979)
Type: Home Computer
Operating system: Sinclair BASIC
CPU: Z80 @ 3.25 MHz (most machines used the NEC μPD780C-1 equivalent)
Memory: 4K ROM, 1K RAM (externally expandable to 16K)
Display: 24 lines x 32 character text display Monochrome only
Sound: None, I/O Z80 bus, 250 baud cassette interface, RF television out
Storage: External cassette recorder
Very slow program execution - no video chips, the CPU performs all of the computer functions
The keyboard is a membrane-type, a flat plastic surface which is difficult to use and wears-out rather quickly.
There was an upgrade kit to the ZX81 as can be seen in the last photo.