Congratulations! You have just finished the last chapter in Introduction to Digital Computers. In this chapter you learned about many things that were mentioned in other chapters, without a detailed explanation. This was done intentionally, as some of the subjects would have been too difficult and hard to understand without background knowledge. Through your study of chapters 1, 2, and 3, you gained enough knowledge to understand chapter 4. This chapter should have answered a lot of questions for you and made certain subjects more clear.
DATA is a general term used to describe raw facts like your service number, name, and paygrade.
SOURCE DATA is raw data typically written on some type of paper document.
DATA REPRESENTATION is accomplished by the use of symbols. The symbol itself is not the information, but merely a representation of it. Symbols convey meaning only when understood. In computers, symbols are represented by CODES.
COMPUTER CODING SYSTEMS are used to represent numeric, alphabetic, and special characters in computer storage and on magnetic media.
EXTENDED BINARY CODED DECIMAL INTERCHANGE CODE (EBCDIC) is an 8-bit code used in computers to represent numbers, letters, and special characters.
AMERICAN STANDARD CODE FOR INFORMATION INTERCHANGE (ASCII) is another 8-bit code developed to standardize a binary code to give the computer user the capability of using several machines to process data regardless of the manufacturer.
A PARITY (CHECK) BIT is used to detect errors in computer circuitry.
MAGNETIC CORE STORAGE is used as primary storage in some computers.
PRIMARY STORAGE CAPACITY AND ADDRESSES are designed and built into the computer by the manufacturer.
Computers may be WORD-ADDRESSABLE, CHARACTER-ADDRESSABLE, or FLEXIBLE.
Data in SECONDARY STORAGE like disk or tape is normally organized by bits, characters (bytes), fields, records, and files.
STORAGE ACCESS METHODS vary with the types of media and devices you are using.
SEQUENTIAL-ACCESS STORAGE is associated with punched cards, paper tape, and magnetic tape.
DIRECT-ACCESS STORAGE is obtained by using magnetic disks and drums.
RANDOM-ACCESS STORAGE refers to magnetic core, semiconductor, thin film, and bubble storage.
A NETWORK is any system composed of one or more computers and terminals; however, most are composed of multiple terminals and computers.
LOCAL AREA NETWORKS (LANs) allow dissimilar machines to exchange information within one universal system within a building or small geographic area.
WIDE AREA NETWORKS provide for global connections and are sometimes referred to as global networks.
A MODEM converts the digital signal produced by your terminal or the computer to an audio signal suitable for transmission over a communications line. It also converts the audio signal back to a digital signal before it is supplied to your terminal or computer.