Introduction to Computing, Part 19
Question 1: Explain how words and letters are represented digitally.
Answer 1: On a computer, all information is represented digitally as a series of ones and zeros. This includes all of the information used in arithmetic operations, as well as letters, symbols, and numerals. These latter three types of information are known collectively as character data. Though appearing complicated to the human eye, binary code is the easiest way for a computer to store and communicate data. Computers use several different styles of code for character data, including ASCII (American Standard Code for Information Interchange), which represents each character as a seven-bit sequence; Extended ASCII, which represents every character as an eight-bit sequence; EBCDIC (Extended Binary-Coded Decimal Interchange), used formerly by IBM mainframes; and Unicode, which represents every character as a sixteen-bit sequence.
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Question 2: Explain why ASCII and Extended ASCII not only represent letters and symbols, but also have codes for the numbers zero through nine.
Answer 2: ASCII and Extended ASCII are used to represent the numerals zero through nine because these numerals are often required for reasons other than arithmetic. For instance, a computer might need to display a telephone number as a seven-digit sequence. In ASCII, each digit in the phone number would be represented in a seven-bit sequence, while in Extended ASCII each digit would be represented by an eight-bit sequence. The digits in a phone number are never added or subtracted, though they are identical to the numbers used for these functions. For this reason, binary codes need to be able to represent numerals for non-arithmetic purposes.
Question 3: Explain how bits are able to store sound and images.
Answer 3: In order to be stored, images and sounds have to be digitized. Images are subdivided into pixels, each of which is assigned a binary number depending on its color. Sounds, on the other hand, are broken down into wave components. The samples taken from various points along the wave are converted into digital values. In order to represent a specific sound in sufficient detail, a computer must digitize thousands of wave samples every second.
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