A
computer is a
machine that changes
information according to well defined
rules. Computers have existed for much of human
history. Examples of early computers are the
astrolabe and the
abacus. Modern computers have changed very much. They are able to control
traffic lights,
cars or
locks. Most modern computers can be used to play
music or
video. The basic principle is still the same though: the computer has a set of rules, usually called an
algorithm. The computer changes information based on these rules.
A person uses a computer by telling it to do things, like playing movies or going to Wikipedia. Computers do not know English, so people must tell their computers to do things by speaking the computer's language. The computer's language is called a
programming language.
Programmers know this computer's language, and use it to write programs that tell the computer what to do. Normal people use the programs that a programmer wrote to tell the computer what to do.
Computers can do anything that someone can tell them to do. Computers are able to solve
mathematical problems because a programmer has told them how to solve math problems. Because computers are very fast, modern computers can solve billions of math problems per second. Computers are used to control factories, which in the past were controlled by humans. They are also in homes, where they are used for things such as listening to music, reading the news, and writing.
[change] History of computing
Nobody knows who built the first computer. This is because the word "computer" used to mean a person who did math as their job (a human computer). Because of this, some people say that humans were the first computers. Human computers got bored doing the same math over and over again, and made tools (mostly mechanical calculating devices like
abacuses) to help them get the answers to their problems.
[change] Automation
Humans have a problem with math. To show this, try doing 584 x 3,220 in your head. It is hard to remember all the steps! People made tools to help them remember where they were in a math problem. The other problem people have is that they have to do the same problem over and over and over again. A cashier used to make change every day in her head or with a piece of paper. That took a lot of time and people made mistakes. So people made machines that did those same things over and over. This part of computer history is called the "history of automated calculation," which is a fancy phrase for "the history of machines that make it easy for me to do this same math problem over and over without making mistakes."
The
abacus, the
slide rule, the
astrolabe and the
Antikythera mechanism (which dates from about 150-100 BC) are examples of automated calculation machines.
[change] Programming
Some people did not want a machine that would do the same thing over and over again. For example, a music box is a machine that plays the same music over and over again. Some people wanted to be able to tell their machine to do different things. For example, they wanted to tell the music box to play different music every time. They wanted to be able to program the music box- to order the music box to play different music. This part of computer history is called the "history of programmable machines" which is a fancy phrase for "The history of machines that I can order to do different things if I know how to speak their language."
One of the first examples of this was built by
Hero of Alexandria (c. 10–70 AD). He built a mechanical theater which performed a play lasting 10 minutes and was operated by a complex system of ropes and drums. These ropes and drums were the language of the machine- they told what the machine did and when. Some people argue that this is the first programmable machine.
[1]
Most historians agree that the "castle clock", an
astronomical clock invented by
Al-Jazari in 1206, is the first known
programmable analog computer.
[2] It showed the
zodiac, the
solar and
lunar orbits, a
crescent moon-shaped
pointer travelling across a gateway that made some
doors to open every
hour,
[3][4] and five
robotic musicians who play music when
levers hit them. The length of
day and
night could be changed (AKA re-programmed) every day in order to account for the changing lengths of day and night throughout the year.
[2] Some people
[who?] consider
Ada Lovelace to be the first
programmer.
[source?]
[change] The Computing Era
At the end of the
Middle Ages, people in Europe thought math and
engineering were more important. In 1623,
Wilhelm Schickard made a mechanical calculator. Other Europeans made more calculators after him. They were not modern computers because they could only add, subtract, and multiply- you could not change what they did to make them do something like play tetris. Because of this, we say they were not programmable.
In 1801,
Joseph Marie Jacquard used
punched paper cards to tell his
textile loom what kind of pattern to weave. He could use punch cards to tell the loom what to do, and he could change the punch cards, which means he could program the loom to weave the pattern he wanted. This means the loom was programmable.
Modern computers were made when someone (
Charles Babbage) had a bright idea. He wanted to make a machine that could do all the boring parts of math, (like the automated calculators) and could be told to do them different ways (like the programmable machines.)
Charles Babbage was the first to make a design of a fully programmable mechanical computer. He called it the "The
Analytical Engine".
[5] Because Babbage did not have enough money and always changed his design when he had a better idea, he never built his Analytical Engine.
As time went on, computers got more and more popular. And that stands out at the beginning. This is because people get bored easily doing the same thing over and over. Imagine spending your life writing things down on index cards, storing them, and then having to go find them again. The U.S. Census Bureau in 1890 had hundreds of people doing just that. People got very bored and very frustrated, and would say, "There HAS to be an easier way to do this." Then some bright person figured out how to make machines do a lot of the work.
Herman Hollerith figured out how to make a machine that would automatically add up information that the Census bureau collected. The
Computing Tabulating Recording Corporation(which later became
IBM) made his machines, and everyone was happy. At least, they were happy until their machines broke down, got jammed, and had to be repaired. This is when the
Computing Tabulating Recording Corporation invented tech support.
Because of machines like this, new ways of talking to these machines were invented, and new types of machines were invented, and eventually the computer that we all know and love today was born.
[change] Analog and Digital Computers
In the first half of the 20th century, scientists started using computers, mostly because scientists had a lot of math to figure out and wanted to spend more of their time thinking about the secrets of the universe instead of spending hours adding numbers together. If you remember getting bored doing your times tables, you will know exactly how they felt.
So they put together computers. These computers used
analog circuits, which made them very hard to program. Then, in the 1930s, they invented
digital computers, which made them easier to program.
[change] High-scale computers
Scientists figured out how to make and use digital computers in the 1930s and 1940s. Scientists made a lot of digital computers, and as they did, they figured out how to ask them the right sorts of questions to get the most out of them. Here are a few of the computers they built:
EDSAC was one of the first computers that remembered what you told it even after you turned the power off. This is called (
von Neumann) architecture.
- Konrad Zuse's electromechanical "Z machines". The Z3 (1941) was the first working machine that used binary arithmetic. Binary arithmetic means using "Yes" and "No." to add numbers together. You could also program it. In 1998 the Z3 was proved to be Turing complete. Turing complete means that it is possible to tell this particular computer anything that it is mathematically possible to tell a computer. It is the world's first modern computer.
- The non-programmable Atanasoff–Berry Computer (1941) which used vacuum tubes to store "yes" and "no" answers, and regenerative capacitor memory.
- The secret British Colossus computers (1943)[6], which you could kind of sort of program. It showed that even though it had thousands of tubes, it still worked most of the time. It was used for breaking German wartime codes.
- The Harvard Mark I (1944), A big computer that you could kind of program.
- The U.S. Army's Ballistics Research Laboratory ENIAC (1946), which could add numbers the way people do (using the numbers 0 through 9) and is sometimes called the first general purpose electronic computer (since Konrad Zuse's Z3 of 1941 used electromagnets instead of electronics). At first, however, the only way you could reprogram ENIAC was by rewiring it.
Several developers of ENIAC saw its problems. They invented a way to for a computer to remember what they had told it, and a way to change what it remembered. This is known as "stored program architecture" or
von Neumann architecture.
John von Neumann talked about this design in the paper
First Draft of a Report on the EDVAC, distributed in 1945. A number of projects to develop computers based on the stored-program architecture started around this time. The first of these was completed in
Great Britain. The first to be demonstrated working was the
Manchester Small-Scale Experimental Machine (SSEM or "Baby"), while the
EDSAC, completed a year after SSEM, was the first really useful computer that used the stored program design. Shortly afterwards, the machine originally described by von Neumann's paper—
EDVAC—was completed but was not ready for two years.
Nearly all modern computers use the stored-program architecture in some form. It has become the main
concept which defines a modern computer. Most of the technologies used to build computers have changed since the 1940s, but many current computers still use the von-Neumann architecture.
In the 1950's computers were built out of mostly
vacuum tubes.
Transistors replaced vacuum tubes in the 1960's because they were smaller and cheaper. They also need less power and do not break down as much as vacuum tubes. In the 1970s, technologies were based on
integrated circuits.
Microprocessors, such as the
Intel 4004 made computers smaller and cheaper. They also made computers faster and more reliable. By the 1980s, computers became small and cheap enough to replace mechanical controls in things like
washing machines. The 1980s also saw
home computers and
personal computer. With the evolution of the
Internet, personal computers are becoming as common as the
television and the
telephone in the household.
In 2005 Nokia started to call some of its mobile phones (the N-series) "multimedia computers" and after the launch of the Apple
iPhone in 2007, many are now starting to add the
smartphone category among "real" computers. In 2008, if the category of smartphones are included in the numbers of computers in the world, the biggest computer maker by units sold, is no longer Hewlett-Packard, but rather Nokia.
[source?]
[change] Kinds of computers
There are three types of computers: desktop computers, mainframes, and embedded computers.
A "desktop computer" is a small machine that has a screen (which is not part of the computer). Most people keep them on top of a desk, which is why they are called "desktop computers." "Laptop computers" are computers small enough to fit on your lap. This makes them easy to carry around. Both laptops and desktops are called personal computers, because one person at a time uses them for things like playing music, surfing the web, or playing video games.
There are bigger computers that many people at a time can use. These are called "Mainframes," and these computers do all the things that make things like the internet work. You can think of a personal computer like this: the personal computer is like your skin: you can see it, other people can see it, and through your skin you feel wind, water, air, and the rest of the world. A mainframe is more like your internal organs: you (hopefully) never see them, and you barely even think about them, but if they suddenly went missing, you would have some very big problems.
There is another type of computer, called an embedded computer. An embedded computer is a computer that does one thing and one thing only, and usually does it very well. For example, an alarm clock is a embedded computer: it tells the time. Unlike your personal computer, you cannot use your clock to play Tetris. Because of this, we say that embedded computers cannot be programmed, because you cannot install programs like Tetris on your clock. Some
mobile phones,
automatic teller machines,
microwave ovens,
CD players and
cars are examples of embedded computers.
[change] Common uses of home computers
[change] Working methods
Computers store data and the instructions telling them what to do with the data as numbers, because computers can do things with numbers very quickly. These data are stored as
binary symbols (1s and 0s). A 1 or a 0 symbol stored by a computer is called a
bit, which comes from the words binary
digit. Computers can use many bits together to represent instructions and the data that these instructions use. A list of these instructions is called a
program and stored on the computer's
hard disk. Computers use
memory called "
RAM" as a space to carry out the instructions and store data while it is doing these instructions. When the computer wants to store the results of the instructions for later, it uses the
hard disk.
An
operating system tells the computer how to understand what jobs it has to do, how to do these jobs, and how to tell people the results. It tells the electronics inside the computer, or "
hardware", how to work to get the results it needs. This lets most computers have the same
operating system, or list of orders to tell it how to talk to the user, while each computer can have its own computer programs or list of jobs to do what its user needs. Having different programs and
operating systems makes it easy to learn how to use computers for new things. When a user needs to use a computer for something different, the user can learn how to use a new program.
[change] The Internet
One of the most important jobs that computers do for people is helping with
communication. Communication is how people share
information. Computers have helped people move forward in
science,
medicine,
business, and
learning, because they let experts from anywhere in the world work with each other and share information. They also let other
people communicate with each other, do their jobs almost anywhere, learn about almost anything, or share their opinions with each other. The
Internet is the thing that lets
people communicate between their computers.
[change] Computers and waste
A computer is now almost always an
electronic device. It usually contains materials that will become
toxic waste when disposed of. When a new computer is bought in some places, laws require that the cost of its
waste management must also be paid for. This is called
product stewardship.
Computers can become
obsolete quickly, depending on what programs the user runs. Very often, they are thrown away within two or three years, because newer programs require a more powerful computer. This makes the problem worse, so
computer recycling happens a lot. Many projects try to send working computers to
developing nations so they can be re-used and will not become waste as quickly, as most people do not need to run new programs.
[change] Main hardware
Computers come in different forms, but most of them have a common design.
- All computers have a CPU
- All computers have some kind of data bus which lets them get inputs or output things to the environment.
- All computers have some form of memory. These are usually chips (integrated circuits) which can hold information.
- Many computers have some kind of sensors, which lets them get input from their environment.
- Many computers have some kind of display device, which lets them show output. They may also have other peripheral devices connected.
A computer has several main parts. When comparing a computer to a human body, the
CPU is like a brain. It does most of the 'thinking' and tells the rest of the computer how to work. The CPU is on the Motherboard, which is like the skeleton. It provides the basis for where the other parts go, and carries the
nerves that connect them to each other and the CPU. The motherboard is connected to a power supply, which provides
electricity to the entire computer. The various drives (
CD drive,
floppy drive, and on many newer computers,
USB drive) act like eyes, ears, and fingers, and allow the computer to read different types of storage, in the same way that a human can read different types of books. The
hard drive is like a human's memory, and keeps track of all the data stored on the computer. Most computers have a
sound card or another method of making sound, which is like vocal cords, or a voice box. Connected to the sound card are
speakers, which are like a mouth, and are where the sound comes out. Computers might also have a
graphics card, which helps the computer to create visual effects, such as 3D environments, or more realistic colors, and more powerful graphics cards can make more realistic or more advanced images, in the same way a well trained artist can.
