Electronic Brains

Electronic Brains

WHEN COMPUTERS WERE STILL A NEW IDEA, they were such a marvel that people called them “electronic brains.” It was the ability of a thermionic valve to switch an electric current on or off that became key to the development of the first generation of true computers, in the 1940s. These valves stored data in computers and performed calculations. Transistors were invented in 1947 and did the same job, but were smaller and more reliable. They heralded the second generation of computers.

THE BINARY SYSTEM

THE BINARY SYSTEM
Computers store and process data by setting electronic switches in different patterns, using a coding system called binary. An electronic switch can only be in two states—“on” and “off.” In binary, the on state is number one and the off state is zero, as seen in this diagram of a binary switch. Groups of switches represent patterns of Is and Os, and these sequences in turn stand for numbers and letters. For example, 101 is the number five.

CALCULATING WITH BINARY

CALCULATING WITH BINARY
The valves in early computers were connected together to form electronic circuits called logic gates that made calculations using binary numbers. The sums were used to process all kinds of data. Sums look very different in binary. 1+2=3 is written as 1+10=11. All computers still use logic gates and binary numbers.

Pilot ACE Pilot ACE

SYSTEMS WITH VALVES
In 1950, computer pioneer Alan Turing built a valve-based computer called the Pilot ACE. It used 800 valves and helped scientists solve physics problems for many years. Bigger machines used far more valves. The AN/FSQ-7 was one of the largest computers ever built. Used by the US Air Force, it contained around 55,000 valves and weighed more than 245 tons (223 metric tons). The valves in such computers produced so much heat that they burned out and stopped the computers from working every few hours.

A PIONEERING INVENTION

A PIONEERING INVENTION
This is a false-color X-ray of a vacuum tube used in early radios. Early vacuum tubes, or thermionic valves, gave rise to the more complex ones used in computers. Thermionic valves can be used to stop or allow a flow of electricity, letting them act as switches. In first-generation computers, each valve switched one bit of data (see page 16 ). A series of valves stored data in the form of a sequence of Is and 0s. As a program ran, the valves would switch on or off as the numbers they held changed. The valves could control each other and be built into useful computer circuits.

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THE NEXT GENERATION

THE NEXT GENERATION
Like valves, transistors can also be used as switches. They work by using semiconductors—materials that carry an electric current sometimes, and block it at other times. Electricity flows into the transistor through one terminal and out through the second, but only if the transistor is switched on first by sending electricity through the third terminal. Transistors did what valves could, but were smaller, faster, cheaper, more reliable, and wasted less energy than valves. Transistors led to a whole new generation of faster computers, and tiny ones are present in most modern computer circuits.

THE FIRST BUG

THE FIRST BUG
On September 9,1947, the Harvard Mark II computer encountered a problem and stopped working. When its operators investigated, they discovered a bug—a moth—that had gotten stuck between the computer’s relays. Ever since then, the word “bug” has been used to refer to problems in a computer, mainly to those caused by errors in computer programming. The process of checking and removing errors from computer programs is known as “debugging.”

TRANSISTORS IN ACTION

TRANSISTORS IN ACTION
It was only when people put transistors into computers in the 1950s that the machines became reliable enough to be really useful. Soon, several large companies began using them. International Business Machines (IBM), a computer-making company, tripled in size in the 1950s. American Airlines used an IBM 7090 computer (left) to reserve plane seats, carrying out the world’s first online bookings in 1964.

RUNNING FAST

RUNNING FAST
Built by Control Data Corporation (CDC), the CDC 6600 was the first successful supercomputer (see pages 30 -31 ), capable of performing more than 1 million instructions in a second—today’s supercomputers can perform more than 1 quadrillion calculations in a second. This machine contained about 400,000 transistors based on the element silicon, instead of the germanium transistors that earlier computers used. More than 100 machines were sold, mostly to academic and military research laboratories. The CDC 6600 was the fastest computer in the world between 1964 and 1969.

Before Computers

Before Computers

FOR THOUSANDS OF YEARS, people have invented machines to simplify mathematical calculations. The abacus first appeared in Mesopotamia around 2700 BCE. The ancient Greeks built mechanical devices capable of solving particular mathematical problems and, by the 17th century, people were using craftsmanship, developed while building mechanical clocks, to make complicated calculating machines. For many centuries, these machines could do no more than give the answer to a particular equation. In the 19th century, Charles Babbage came up with the idea of a machine that could do many kinds of calculation by following a whole series of instructions—which could be changed as required. Babbage called such machines analytical engines—we call them computers.

KEEPING COUNT

KEEPING COUNT
For many thousands of years, people have counted all kinds of things, from days to loaves of bread, and they have drawn or scratched lines, called tallies, on pieces of wood or bone to record the answers. This bone is over 20,000 years old and was found at Ishango in Africa. Scientists believe that people used it to record the phases of the Moon.

Chinese abacus Chinese abacus

COUNTING BEADS
Invented more than 4,000 years ago, the abacus is one of the oldest calculating devices. In this 19th-century Chinese abacus, beads represent specific numbers. The column on the extreme right stands for the number of ones in a number, the column to its left is tens, the next, hundreds, and so on. The user enters numbers by sliding the beads toward the crossbar. The abacus is used to represent numbers, and also to perform calculations including addition, subtraction, division, and multiplication.

ANCIENT SKY TRACKER

ANCIENT SKY TRACKER
The Antikythera mechanism is an amazingly advanced device built some time between 150 and 100 BCE, perhaps on the island of Rhodes. Divers recovered it in 1900 from a sunken Roman ship, which was wrecked off the island of Antikythera around 70 BCE. This device used a complicated arrangement of moving parts called gears (toothed wheels that interlock with one another) to calculate and display the positions of the Sun and the Moon, along with those of the major stars and perhaps also of the planets. It was so corroded by the sea that scientists needed many years of study to understand its function and mechanism. In 2007, a reconstruction of the device was presented to the National Hellinic Research Foundation in Athens, Greece. Incredibly, it worked perfectly.

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STAR MACHINE

STAR MACHINE
The Moorish astronomer Abu Ishaq Ibrahim al-Zarqali built this device—called an astrolabe—in about 1015 CE. Astrolabes were movable models of the sky. Ancient Greeks invented the earliest astrolabes in around 150 BCE, and such devices were in use in many countries until the 16th century CE. Astrolabes had many uses. If they were set with the position of a particular star over a place, or that of the Sun, they would display the time at that place. They also showed the stars that were visible at specific times from particular places on Earth. This probably helped travelers find out where they were. Astrolabes were a little like simple calculators, in that they displayed an answer on being fed with data.

Napiers bones Napier’s bones

NAPIER’S BONES
In 1617, John Napier invented a set of square columns called Napier’s bones. Each bone was divided into nine squares, with the top square carrying a number between zero and nine. The squares below contained multiples of that number. Napier’s bones helped perform multiplication and division. To multiply 548 by 5, for instance, a person would place these three bones on a board. The board had a column of nine squares on the left, marked 1–9. The user would then look at the squares on the bones that were next to the fifth position on the board. He or she would read the digits from left to right, adding the digits within the slanting lines. In this case, the answer would read as 2,740.

CALCULATING TAX

CALCULATING TAX
The Pascaline was a mechanical calculator that could add or subtract numbers. Blaise Pascal, a philosopher and mathematician, developed the device in 1642 to help his father carry out calculations for taxation. The machine was quite difficult to use and so Pascal only managed to sell a few of them. However, the Pascaline spurred the development of more advanced devices, which finally led to the creation of the first computers.

DIFFERENCE ENGINE

DIFFERENCE ENGINE
I In 1822, mathematician Charles Babbage built a prototype calculating machine, seen here. He used it to test out the working of a larger machine—Babbage’s first Difference Engine—that he could not build due to a lack of funds. The engine used a system of gears to calculate tables of mathematical data. In 1991, the London Science Museum followed Babbage’s plans and built the second Difference Engine—which worked perfectly. Babbage also designed—but did not build—what is considered by many to be the first true computer. Babbage called this the Analytical Engine. As a result, he is often known as the father of computing.