User:Amandelpiero

A computer is a machine that is able to take information (input), do some work on or make changes to the information, to make new information (output). Computers have existed for much of human history. Examples of early computers are the astrolabe and the abacus. Modern computers are very different from early computers. They are now very powerful machines that are able to do billions of calculations every second. Most people have used a personal computer in their home or at work. Computers are useful for many different jobs where automatic functions are useful. Some examples are controlling traffic lights, vehicle computers, security systems, Washing machines and Digital Televisions. A person (called a user) can control a computer by telling it to do things. Some ways of controlling a computer are with a keyboard, mouse, buttons, touch screen. Some very new computers can also be controlled with voice commands or hand gestures. Computers can be designed to do anything with information. 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. Modern computers are electronic machines. A computer is only useful if it has both hardware and software. Hardware is the physical parts the computer is made of - for example keyboard, mouse, screen, tower. Software is the computer programs (mathematical instructions). Software uses the hardware by taking input and changing it in to useful output. Computers are able to do billions of calculations each second. They can do mathematical arithmetic very quickly but computers do not really "think". They only follow the instructions in their software programs. Computer programs are designed or written by computer programmers. Computer programs can be written in the computer's own language called machine code. Machine Code has only a few instructions and is based on logic and Mathematical arithmetic. Using machine code is difficult for most human programmers. Today, programmers usually write programs using a programming language like C++, Java or BASIC. These programming languages can be translated in to machine code later using a program called a compiler. 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. Most historians agree that the "castle clock", an astronomical clock invented by Al-Jazari in 1206, is the first known programmable analog computer. 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, 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. Some people[who?] consider Ada Lovelace to be the first programmer.