Computers

Computers started as calculators, and were almost as big as a house. The first one was created by Charles Babbage. The first home computers were issued by Apple, and the internet wasn't used until the late 1980s. Before then, they were used for calculating numbers and typing words.

Before a computer can be used to solve a problem, it must first be programmed, or prepared for solving the problem by being given a set of instructions. The programs which a computer uses are called software. Hardware is the physical equipment that uses the software. If you do not have good software, then your computer will not be able to do very many things.

Programs and data can also be stored on disks. There are two different types of disks, the compact disk (CD) and the digital versatile disc (DVD). The DVD can store a lot more information than the CD can. CD-Read-Only Memory (CD-ROM) and DVD-Read-Only Memory (DVD-ROM) disks can only be read, which means that the information that is put on the disk cannot be erased and rewritten. In the late 1990's, the CD-Recordable (CD-R) and DVD-Recordable (DVD-R) were created. These disks can be written only once; and the CD-Re-Writable (CD-RW), DVD-Re-Writable (DVD-RW), and DVD-Random Access Memory (DVD-RAM) disks can be written on many times. Compact disks can hold many hundreds of megabytes, and are used, for example, to store the information contained in an entire multivolume encyclopedia or set of reference works, and DVD disks can hold ten times as much as that.

Computers & Binary

Computers read information by using the binary system. When you type on a computer, you are actually typing ASCII code and binary. Binary digits, or bits, are 0 and 1, so that 0, 1, 10, 11, 100, 101, etc. are the same as 0, 1, 2, 3, 4, 5, etc. For example, if you type the number 45, you are actually writing the number 00101101. If you type the word "dog" you are writing the ASCII word 010001000100111101001111! Binary digits are easily expressed in the computer circuitry by the presence (1) or absence (0) of a current or voltage. A set of eight bits one after the other is called a byte; the eight-bit byte makes it so that you have 256 different "on-off" combinations. Each byte can represent one of up to 256 alphanumeric characters. The use of two bytes, or 16 bits, allows a computer to have up to 65,536 characters.