The Ferranti Mark I was a commercial version of the Manchester Baby, the University of Manchester research machine built in 1948.

The Baby processed instructions significantly faster than the computers that preceded it. Before the Baby computers were fed instructions by slow mechanical or manual sources, such as paper-tape. In contrast the Baby could rapidly read programs and data from its electronic memory.

The Ferranti's memory was built from cathode ray tubes (CRT) - that at the time were more commonly used by TV and radar displays. The CRT memory - known as a Kilburn-Williams tube and seen here - writes information in a similar fashion to the way an old CRT TV displays a picture. It fired an electron beam at a phosphor screen to write a binary 0 or 1 - a bit - to memory. The beam alters the distribution of electrical charge on the screen and this change is detected by a metal screen or mesh that sitting alongside the tube.

Because the charge dissipates rapidly the beam had to be constantly fired to keep the bit in memory.

Of course, the memory capacity of the Ferranti was, tiny by modern standards, holding a fraction of the data of a single MP3 album track today. The machine used eight CRTs for its primary memory - each capable of storing 32 40-bit words.

Photo: David Link