- First Generation (1939-1954) - vacuum tube
- Second Generation Computers (1954-1959) - transistor
- Third Generation Computers (1959-1971) - IC
- Fourth Generation (1971-1991) - microprocessor
- Fifth Generation (1991 and Beyond)
In the late 1970s computer systems could be classified into microcomputers, minicomputers and mainframe computers:
A microcomputer: a single user computer system (cost L2000 to L5000) based on an 8-bit microprocessor (Intel 8080, Zilog Z80, Motorola 6800). These were used for small industrial (e.g. small control systems), office (e.g. word-processing, spreadsheets) and program development (e.g. schools, colleges) applications.
A minicomputer: a medium sized multi-user system (cost L20000 to L200000) used within a department or a laboratory. Typically it would support 4 to 16 concurrent users depending upon its size and area of application, e.g. CAD in a design office.
A mainframe computer: a large multi-user computer system (cost L500000 upwards) used as the central computer service of a large organisation, e.g. Gas Board customer accounts. Large organisations could have several mainframe and minicomputer systems, possibly on different sites, linked by a communications network.
Introduction to Digital Computer System
by Dr Sheikh Sharif Iqbal
http://faculty.kfupm.edu.sa/EE/sheikhsi/EE_390_Digital_System_Engineering/Extra_lecture_1.pdf
Early computing devices were mechanical machines with gears and levers (such as Abacus and slide-rule, that is also available today as toys)
“Colossus Mark-I” was the 1st electronic computer, used during World War 2 (1943) to decipher military codes. It had 1500 Vacuum tubes and could process 5000 characters/second.
“ENIAC” was a reprogrammable digital computer, built in 1946 to calculate the artillery firing tables of US army. This huge device had 17468 vacuum tubes, 1500 relays, 70000 resistors, 10000 capacitors and consumed almost 150 kilowatt power. (ENIAC was able to store a maximum of twenty 10-digit decimal numbers and could discriminate the sign of a number, compare quantities for equality, add, subtract, multiply, divide, and extract square roots)
*(ENIAC = Electronic Numerical Integrator and Computer)
Hyperlinked data: Vacuum tube looks like light bulbs and generally used to amplify, or otherwise modify, a signal by controlling the movement of electrons in an evacuated space. Currently the vacuum tube has been replaced by the much smaller and less expensive transistor, either as a discrete device or in an integrated circuit.
Hyperlinked data: Electronic Numerical Integrator and Computer
“UNIVAC” was the 1st commercial mainframe computer used by US government in 1951. It used 5200 vacuum tubes that required 125 kW of power to perform 1900 operations per second. (It was able to store 1000 words of 12 characters and running on a clock of 2.25 MHz. This 13 ton device was priced in the range of 100’s of thousands of dollar)
*(UNIVAC = UNIVersal Automatic Computer)
“IBM 650” was the 1st mass produced computer as 2000 of this computers were manufactured and supplied from 1953 to 1962. (It consisted of a console unit, power unit, rotating drum memory and a card reader unit and processed 17,000 instructions per second.)
Complete History: http://library.thinkquest.org/18268/History/hist_c_50s.htm (In that same period, several other companies in different countries were also involved in the development process of digital computers and a complete description can be found in the given URL:
In 1954, the advent of commercial silicon based junction transistors introduced the 2nd generation of computers, where vacuum tubes were replaced with junction transistors.
In 1955, the 1st fully transistorized digital computer, “TRADIC”, was manufactured using almost 700-800 transistors and 10000 diodes. (This 3 cubic feet device was about twenty times faster than the vacuum tube computers and required less than 100 watts of power)
*(TRADIC = TRAnsistor DIgital Computer or TRansistorized Airborne DIgital Computer)
IBM 7000 series was the 1st transistorized computer made by IBM with one million instructions per second capabilities.
In 1958, the invention of integrated cirucits (IC’s) by Jack Kilby and semiconductor IC’s by Robert Noyce (1959) led to a new generation of commercial computers called Mini-computers. (Through 1960’s this scaled-down versions main-frame computers, equipped with keyboard and monitors, were popular due to its reasonable price (USD 10,000 and upwards), acceptable size and performance)
In 1971, the release of 1st commercial microprocessor (Intel 4004) revolutionized the computer industry and resulted in a new generation of micro-computers, also known as personal computers (PC’s). (Later In 1973, a French company developed “Micral”, a low precession personal computer. Due to its high cost of $1,750, this computer was never marketed)
Microprocessor: Also known as central processing unit (CPU) or the brain of the personal computer. It is an integrated circuit built on a tiny piece of silicon and contains thousands, or even millions, of transistors, which are interconnected via superfine traces of aluminum. These transistors work together to store and manipulate data so that the microprocessor can perform a wide variety of useful functions as dictated by software.
In 1977, 1st desktop computer, “TRS-80”, was released with most of the required accessories and an inbuilt programming language “BASIC”. (At a price 600 USD, nearly 10,000 of these machines were sold around the world)
In 1981, IBM’s 1st PC was marketed. It ran on Intel’s 4.77 MHz 8088 microprocessor and came with MS-DOS operating system. The main components of PC’s are briefly introduced in the next slide.
Technical specifications of Intel 4004: (1) Maximum clock speed is 740 kHz and executed ≈60000 instructions/sec. (2) Register set contains 16 registers of 4 bits each (3) Separate program and data storage with single multiplexed 4-bit bus for transferring: 12- bit addresses, 8-bit instructions and 4-bit data words. (4) Instruction set contains 46 instructions. (5) A Japanese company used them to build calculators.
In recent days, microprocessors (μP) are implemented using very large-scale integrated (VLSI) circuit technology, where millions of transistors are interconnected via superfine traces of aluminum and works together to store and manipulate information as dictated by the controlling software.
The evolution of microprocessors has been known to follow Moore's Law and from the humble beginning as processors in calculators (Intel 4004), microprocessors today dominates most of the digital systems from mainframes to the smallest handheld computers.
Moore’s Law: Gordon E. Moore was the co-founder of “Intel”. His empirical observation that appeared in the “Electronics Magazine of 19 April 1965” stated that the complexity of integrated circuits, with respect to minimum component cost, doubles every 24 months and in fiture all the components of a CPU can be built on a single wafer. This rule is generally followed, unconsciously, since early 1970.
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