A computer is a machine (mostly electronic) that is able to take information (input), and process it to make new information (output). Calculating machines have existed for much of human history. A computer is a programmable machine. The two principal characteristics of a computer are: It responds to a specific set of instructions in a well-defined manner and it can execute a prerecorded list of instructions (a program). Early examples are the astrolabe and the abacus. There are four main processing steps in a computer, and they are: inputting, storage, outputting and processing. Modern computers are very different from early computers. They can do billions of calculations per second. Most people have used a personal computer in their home or at work. Computers do many different jobs where automation is useful. Some examples are controlling traffic lights, vehicle computers, security systems, washing machines and digital televisions. A computer user can control it by a user interface. Input devices include keyboard, mouse, buttons, and touch screens. Some very sophisticated computers can also be controlled with voice commands or hand gestures or even brain signals through electrodes implanted in the brain or along nerves. Computers can be designed to do almost anything with information. Computers are used to control large and small machines 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 computer hardware. They do mathematical arithmetic very quickly but computers do not really "think". They only follow the instructions in their software programs. The software uses the hardware when the user gives it instructions, and gives useful output. Computer programs are designed or written by computer programmers. A few programmers write programs in the computer's own language called machine code. Most programs are written using a programming language like C++, Java, and Fortran. These programming languages are more like the language with which one talks and writes every day. The compiler translates the user's instructions into binary code (machine code) that the computer will understand and do what is needed.