The first digital electronic computer was
built by John Vincent Atanasoff
and his assistant Clifford Berry at Iowa State University between 1937-1942.
The Atanasoff Berry Computer (ABC) used punched
cards for input and output, vacuum tube electronics
to process data in binary format, and rotating drums of capacitors to
store data.
A picture of the Atanasoff Berry Computer, the first
digital electronic computer (built between 1937 and 1942). The card readers/punchers
are on the left, a memory drum is in the back, and the vacuum tube processing
electronics in seen in the lower right.
The ABC, however, only performed one task: it was built
to solve large systems of simultaneous equations (up to 29 equations
with 29 unknowns), an onerous computing task commonly found in science
and engineering. So, the ABC was not a general-purpose computer.
Similarly, another special-purpose electronic computer
named Colossus was built in England starting in 1943 for the purpose
of breaking German codes. The project was worked on by Alan Turing and
Max Newman. The existence of this computer was kept secret until the
1970’s.
ENIAC: The first General-Purpose Electronic Computer
The first general-purpose digital
electronic computer, one that could be programmed to perform a variety
of calculational tasks, was the ENIAC (Electronic
Numerical Integrator And Calculator). It was designed and built in the
Fall of 1945 by John Mauchly and J. Presber Eckert. ENIAC was originally
built to calculate ballistic tables for the US military to aim their big
guns.
ENIAC was a monster of a machine, filling a large room
and weighing 30 tons. It included 18,000 vacuum tubes and used 200 kilowatts
of electrical power (the lights dimmed in its Philadelphia neighborhood
when it was first turned on). ENIAC was the first general-purpose computer
because it could be programmed (given
different sets of instructions to follow) by the cumbersome procedure
of reconnecting cables and flipping switches.
Later computers were much more flexible because they incorporated the
idea of stored programs, conceived in 1945
by mathematician John Von Neumann (who worked on the Manhattan Project
in Los Alamos). In this scheme, both the data being manipulated and the
program of instructions for the computer are stored in memory. Modern
computers use this same method.
Mauchly and Eckert later went on to work for the Univac division of
Remmington Rand corporation. The Univac I (Universal
Automatic Computer) was the first commercial computer, coming out in
1951.
Most of these early mainframes were purchased (or rented) by government
bureaus, the military, research labs (such as Los Alamos National Lab),
large corporations, and universities.
IBM (International Business Machines) entered
the computer market in 1953 with its 701 computer. By 1960, IBM was the
dominant force in the market of large mainframe computers. Smaller players
in the mainframe market included Burroughs, Control Data, General Electric,
Honeywell, NCR, RCA, and Univac.
Transistors and Integrated Circuits
Vacuum tubes consume lots of electrical
power and are prone to burning out, which caused problems for early computers
that used thousands of them. By 1960, the transistor replaced
the vacuum tube as the electrical switching device in computers. The
transistor (developed at Bell Labs by William Shockley and others in
the 1950’s)
is a solid-state semiconductor device typically made of silicon or germanium.
It is much smaller, much more reliable, and consumes much less energy
than a vacuum tube. A vacuum tube computer that
previously filled a sizable portion of a room could be replaced by a transistorized
computer system that filled a few cabinets. A good example of an early
computer using transistors is the IBM 360, which dominated the mainframe
computer market in the mid to late 1960’s.
The early 1960’s also
saw the development of the microchip,
or integrated circuit (IC),
invented by Jack Kirby and Robert Noyce. An integrated circuit incorporates
many transistors and other electrical components, all formed into a miniature
circuit onto a single chip of silicon.
Below is a picture of an Integrated Circuit (IC), also
called a microchip. This particular IC is an old erasable programmable
read-only memory chip. The IC package has a window that allows the memory
to be erased by exposing the chip to ultraviolet light. This window also
allows us to see the tiny silicon chip itself (inset image in upper right).
Notice the tiny wires that connect the chip circuitry to the electrical
contacts (the ‘legs’) of the IC package.
The invention of the integrated circuit allowed computers
to become even smaller, with the whole central processing
unit (CPU) of the computer fitting onto one circuit board. These minicomputers were
cheaper and smaller than a mainframe (the computer was roughly the size
of a drawer in a large filing cabinet). A minicomputer might cost $100,000
instead of the $1,000,000 a mainframe cost, allowing many more businesses
and universities to afford their own computer systems.
The most successful minicomputers were the PDP and Vax
series made by Digital Equipment Corporation (DEC). Minicomputers were
multi-user systems, in much the same way as mainframe
computers, but on a smaller scale.
Minicomputers are now a mainly obsolete class of computer,
having been largely replaced by high-end microprocessor workstations.
Microprocessors
As IC technology progressed, chip manufacturers
could fit more and more circuitry onto the tiny silicon chips. By 1971,
a company named Intel developed the first microprocessor (also
called an MPU) that fit a whole CPU onto
one microchip. The Intel 4004 processor contained 2300 transistors on
a chip of silicon 1/8" x 1/16" in
size.
By 1974, Intel introduced their 8080 chip, a general
purpose microprocessor offering ten times the performance of the earlier
MPU. It was not too long before electronics hobbyists began building
small computer systems based on the rapidly improving microprocessor
chips.
The First Microcomputers
The first commercially available microcomputer
of note was the Altair 8800 computer sold by MITS (Micro Instrumentation
& Telemetry Systems), a company founded by Dr. Ed Roberts that was based
in Albuquerque, New Mexico. The computer was featured on the
cover of the January 1975 issue of Popular Electronics, and was sold
as a kit for $397 or assembled for $439. It used a 2 MHz Intel 8080 processor
and had 256 bytes of RAM.
Remember that a computer can’t do anything without
software, and some companies sprang into existence to fill this need.
One small company of note was formed in Albuquerque by a Harvard dropout
to provide software (a BASIC language) for the Altair computer. The founder’s
name was Bill Gates, and the company he form (along with his partner
Paul Allen) was Microsoft.
Dozens of companies (most of which have long since vanished)
began offering microcomputers for sale, most of them based on the Intel
8080 processor and running the CP/M operating system. Other companies
had proprietary operating systems, such as Radio Shack, Atari, and Commodore.
Of particular note is a company named Apple founded
by Steve Jobs and Steve Wozniak on April 1, 1976. Their Apple II computer
was a hit, especially in the home and education markets.
Two things caused the microcomputer market
to really take off in the late 1970’s and early 1980’s: spreadsheet
software, and the IBM PC. Spreadsheet
software (the first was Visicalc for the Apple II, written by Dan Bricklin) finally
convinced business people that there was a serious use for microcomputers.
The IBM PC, released by in 1981, gave a legitimacy to the microcomputer
by virtue of the IBM name (remember, IBM was the maker
of big mainframe computers; and it was said “Nobody ever gets fired
for buying IBM”). It used a 4.77 MHz Intel 8088 processor.
Microsoft went to IBM about an operating
system (OS) for
their new PC. Bill Gates told them, “Wwe have an OS that will
run on this new machine you are planning,” and made a deal. Microsoft
did not, in fact, have such an OS, but they quickly bought one from a
third party and converted it into PC-DOS. But what Gates did that was
really clever was to make a deal with IBM that allowed Microsoft to also
sell the OS to other companies as
MS-DOS...and Microsoft’s future was set.
IBM PC sales skyrocketed and IBM dominated the market within
two years, releasing the PC XT (1983) and PC AT
(1984) using the Intel 80286 processor.
But, almost as quickly, IBM lost it dominance in the PC
marketplace when other companies (such as Compaq) began to release “PC
compatible” computers (also called “PC clones”).
By 1986 the clones owned most of the market, and IBM never regained its
dominance. Microsoft, on the other hand, supplied their operating systems
to all PCs, becoming a huge corporation.
Graphical User Interface
Computers were traditionally very difficult
to use, requiring the user to memorize and type in the necessary commands
(this is called a Command Line Interface). To make computers more accessible,
the Graphical User Interface (GUI) was developed. In a GUI, the user
interacts with a graphical display on the screen containing icons and
windows and controls. Commands are chosen from menus rather than typed
in.
The GUI was developed at the Xerox Palo Alto Research Center,
but the management at Xerox failed to see the usefulness of it. When
Steve Jobs of Apple saw the GUI, however, he recognized its value.
Apple licensed the concepts from Xerox, developed them further, and
released the first successful GUI computer, the Macintosh,
in 1984. Macintosh computers used the Motorola 68000 series of microprocessors
(and later the PowerPC series of microprocessors).
Microsoft was also quick to realize the worth of a GUI, but
its graphical user interface, Windows, was slow
in displacing DOS on PCs (the first versions of Windows left much to
be desired).
More details about computer hardware and software can be
f0und in other parts of this tutorial.
| 
No comments:
Post a Comment