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Inventors of the Modern Computer
The Manchester Baby
The Williams-Kilburn Tube
Frederick Williams & Tom Kilburn
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By 1946, a winner in the data-storage game emerged that would dominate
the computer field for the next several years. Sir Frederick Williams and
Tom Kilburn co-invented the Williams-Kilburn Tube (or Williams Tube), a
type of altered cathode-ray tube. Scientists conducted research on cathode-ray
tubes serving as computer data storage during the early 1940s.
 The
illustration to the right is an example of the video display terminal used
with the Manchester computer. The terminal mirrored what was happening
within the Williams Tube. A metal detector plate placed close to the surface
of the tube, detected changes in electrical discharges. Since the metal
plate would obscure a clear view of the tube, the technicians could monitor
the tubes used a video screen. Each dot on the screen represented a dot
on the tube's surface; the dots on the tube's surface worked as capacitors
that were either charged and bright or uncharged and dark. The information
translated into binary code (0,1 or dark, bright) became a way to program
the computer.
The
Williams Tube provided the first large amount of random access memory (RAM),
and it was a convenient method of data-storage. It did not require rewiring
each time the data was changed, and programming the computer went much
faster. It became the dominant form of computer memory until outdated by
core memory in 1955.
History of the Manchester Baby
In December 1946, Williams began to chair the Department of Electrical
Engineering at the University in Manchester, England, with Tom Kilburn
moving to Manchester as well. The men had both worked for the Telecommunications
Research Establishment (TRE) in Malvern, England, trying to improve the
digital storage ability of a cathode-ray tube.
Williams
had already succeeded in storing one bit of information on a cathode-ray
tube and had filed a provisional patent in December of 1946. Tom Kilburn
soon devised an improved method of storing bits, increasing the storage
capacity to 2048 bits. Williams added Kilburn's name to the patent. The
team was ready to build a computer based on the Williams Tube.
In
1948, Tom Kilburn, assisted by another TRE researcher, Geoff Tootill, worked
on designing and building a prototype machine. Nicknamed "The Baby," the
new computer demonstrated the ability of the Williams Tube. For the first
time in history, a computer used a stored program. Kilburn wrote the computer
program, first executed on June 21, 1948.
Baby's Specifications
32-bit word length. |
Serial binary arithmetic using 2 complement integers. |
Single address format order code. |
Random access main store of 32 words, extendable up to 8192 words. |
Computing speed of around 1.2 milliseconds per instruction. |
The
team designed a second computer (Manchester Mark 1) and commissioned an
outside company called Ferranti Ltd. to build the computer in 1949. Ferranti
Ltd. and the Manchester University team collaborated in 1951 and built
the world's first commercially available general-purpose computer called
the Ferranti Mark 1. The first machine off the production line was delivered
to the University of Manchester.
Manchester Mark 1 Specs - Ferranti Mark 1 Specs
Store organized in 40-bit addressable "lines," holding one 40-bit number
or two 20-bit instructions. |
Store organized in 20-bit addressable "lines," an instruction taking
one line and a number two consecutive lines. |
Serial 40-bit arithmetic with hardware add, subtract, and multiply
and logical instructions. |
Serial 40-bit arithmetic, with hardware add, subtract, and multiply
and logical instructions and simple B-line arithmetic. |
2 modifier registers (B-lines, for modifying addresses in instructions.) |
8 modifier registers (B-lines, for modifying addresses in instructions.) |
Single address format order code - about 30 function codes. |
Single address format order code - about 50-function codes. |
4 pages of random access main store. |
8 pages of random access main store. |
128-page capacity drum backing store, 2 pages per track, about 30 milliseconds
revolution time. |
512-page capacity drum backing store, 2 pages per track, about 30 milliseconds
revolution time. |
Standard instruction time - 1.8 milliseconds, multiplication much slower. |
Standard instruction time - 1.2 milliseconds, multiplication 2.16 milliseconds. |
Peripheral Instructions: read and punch a line of 5 hole paper tape;
transfer a given page or track on drum to/from a given Williams Tube "page"
or page pair in store. |
Peripheral Instructions: read and punch a line of 5 hole paper tape;
transfer a given page or track on drum to/from a given Williams Tube "page"
or page pair in store. |
Further
Reading:
Research the biographies of Frederic Calland Williams and Tom Kilburn.
Learn how the Williams-Kilburn Tube operated. Read Tom Kilburn's original
notes for the world's first stored computer program. View pictures of the
Manchester Mark 1 and the Ferranti Mark 1. The complete history of computer
memory.
Inventors of the Modern Computer
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