Language of Computers
This unit examines the way in which information is stored in a computer. The data and information that is part of our day-to-day lives exist in a variety of forms. For example, we interact with printed information, sound, and images. If we are to use this information with a computer, it must be transformed into a form that the computer can use.

Computers use integrated circuits (chips) that include many transistors that act as switches. These transistors are either on or off. Electricity is either flowing through the transistor or it isn't. Thus, a circuit is either open or closed. Something that can have only two states is called binary. The binary number system represents the two states using the symbols 0 and 1. Actually, there are no 0s and 1s inside the computer. Instead, the 0s and 1s represent the state of a transistor switch or a circuit.

Binary Code
The two states available in the electrical switches and circuits, on and off, provide a way to use the binary number system to represent information in a computer. Computer hardware is designed to work with the information after it has been binary-coded. Each of the 0s or 1s from the binary number system is called a bit (binary digit). Whether a computer is working with words, numbers, colors, graphics, or sound, the internal representation of the information is the same—a series of bits made up of 0s and 1s.



You and your students are used to working with a much larger set of symbols than the two symbols a computer uses. The symbol set that you are accustomed to using contains 26 lowercase letters, 26 uppercase letters, 10 digits, a number of punctuation marks, and other symbols such as #, *, &, and =.

At first, you might think that a two-character symbol set is limiting. However, it is not. You can count with binary numbers. The (base 10) numbers 1, 2, 3, and 4 are represented in binary as 1₂, 10₂, 11₂, and 100₂. In addition, just as you do with the base 10 numbers, you can perform mathematical computations on binary numbers using binary arithmetic.

The computer uses a special binary code to represent letters. The computer industry has agreed on an 8-bit code for representing letters and other symbols. The letter “A” is represented by 0100 0001₂ and the letter B by 0100 0010₂. The lowercase of each letter is represented by a different 8-bit code. Similarly, all the other letters can be represented using this 8-bit binary code.

A group of 8 bits is called a byte. There are exactly 256 different 8-bit binary numbers: 0000 0000₂, 0000 0001₂, 0000 0010₂ ... 1111 1110₂, 1111 1111₂. These binary numbers represent the base 10 numbers 0, 1, 2... 254, 255.

In order to provide a way for the keyboard to function as a digital input device, the computer contains special tables that contain information about the letters and other symbols. Each key on the keyboard sits above a grid of wires. When a key is pressed, there is an immediate change in the current moving along the row and column associated with the key. A special keyboard chip scans the row circuits hundreds of times per second and recognizes that a row is now active. After recording which row is active, the chip quickly scans to identify which column is also active. The information of row and column is recorded and transmitted as a key code or scan code.

The microprocessor sends the key code to a look-up table or scan-code table installed in the computer. This table matches the key-location code with a corresponding letter. Each letter is given a numerical value that is converted into binary form. In an English look-up table, the R key is represented in binary code as 0101 0010₂.


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