Generation 1: Vacuum Tubes (1945-1954)

vacuum tubes
COLOSSUS
ENIAC
John von Neumann
RCA transistor ad from Fortune 1953/3
Rear Admiral
Grace Murray-
Hopper
integrated circuits
Intel 4004
In the mid s, electromagnetic relays began to be replaced by vacuum tubes, resulting in machines whose only moving parts were electrons. Invented by Lee de Forest (1873-1961) in 1906, a vacuum tube is a small glass tube from which all or most of the gas has been removed, permitting electrons to move with minimal interference from gas molecules. Since vacuum tubes have no moving parts (only the electrons move, they permitted the switching of electrical signals at speeds far exceeding those of any mechanical device. In fact, vacuum tubes were up to 1,000 times faster than electromagnetic relays. They could also be used to construct fast storage devices.
The stimulus for the electronic (vacuum tube) computer was World War II. The first electronic computer was COLOSSUS, built by British government to decode encrypted Nazi communications. COLOSSUS was designed in part by the British mathematician Alan Turing (1912-1954), who is considered one of the founding fathers of computer science due to his seminal work in the theory of computability and artificial intelligence. While operational in 1943, COLOSSUS's influence over other researchers at the time was limited as its existence remained classified for over 30 years. It contained more than 2,300 vacuum tubes, and had a unique design due to its intended purpose as a code-breaker. It contained 5 different processing units, each of which could read in and process 5,000 characters of code per second. Using COLOSSUS, British Intelligence was able to decode Nazi military communications for extended periods, providing invaluable support to Allied operations during the war.
At roughly the same time in the United States, physics professor John Mauchly (1907-1980) and his graduate student J. Presper Eckert (1919-
1995) designed ENIAC, which was an acronym for Electronic Numerical Integrator And Computer. The ENIAC was designed to compute ballistics tables for the US. Army, but it was not completed until 1946. It consisted of 18,000 vacuum tubes and 1500 relays, weighed 30 tons, and consumed 140 kilowatts of power. In contrast to the Mark I, the
ENIAC could only store 20 numbers in memory, although more than 100 constants could be entered using switches. Still, the ENIAC could perform more complex calculations than the Mark I and operated up to 500 times faster (5,000 additions per second. The ENIAC was programmable in that it could be reconfigured to perform different computations. However, reprogramming the machine required manually setting up to 6,000 multiposition switches and reconnecting cables. Ina sense, it was not so much reprogrammed as it was rewired each time the application changed.
One of the scientists involved in the ENIAC project was John von Neumann (1903-1957), who along with Turing is considered a founding father of the field of computer science. Von Neumann recognized that programming via switches and cables was tedious and error prone. As an alternative, he designed a computer architecture in which the program could be stored in memory along with the data. Although this idea was initially proposed by Babbage with his Analytical Engine, von
Neumann is credited with its formalization using modern designs. Von Neumann also recognized the advantages of using binary (base 2) representation in memory as opposed to decimal
(base 10), which had been used previously. His basic design was used in EDVAC (Eckert and Mauchly at UPenn, 1952), IAS (von Neumann at Princeton, 1952), and subsequent machines.
The von Neumann architecture is still the basis for nearly all modern computers.
As a result of von Neumann's "stored program" architecture, the process of programming a computer became equally if not more important than designing a computer. Before von
Neumann, computers were not so much programmed as they were hardwired to a particular task. With the von Neumann architecture, a program could be read in (via cards or tapes) and stored in the memory of the computer. Reprogramming the computer did not require any reconfiguring, it simply involved reading in and storing anew program for execution. At first, programs were written in machine language,
sequences of sands that corresponded to instructions directly executable by the hardware. While this was an improvement over rewiring, it still required the programmer to write and manipulate pages of binary numbers -- a formidable and error-prone task. In the early s, assembly languages were invented which simplified the programmer's task somewhat by substituting simple mnemonic names for binary numbers.
The early s also marked the birth of the commercial computer industry. Eckert and Mauchly left the University of Pennsylvania to form their own company. In 1951, The Eckert-Mauchly Computer
Corporation (later apart of Remington-Rand, then Sperry-Rand) began selling the UNIVAC I computer. The first UNIVAC I was purchased by the US. Census Bureau, and a subsequent UNIVAC I captured the public imagination when it was used by CBS to predict the 1952 presidential election. Several other companies would soon follow Eckert-Mauchly with commercial computers. It is interesting to note that at this time, International Business Machines (IBM) was a small company producing card punches and mechanical card sorting machines. It entered the computer industry late in 1953, and did not really begin its rise to prominence until the early 1960's.

Download 451.15 Kb.

Share with your friends: