Английский для пользователей компьютеров. Ч.2. Белобородова М.Л - 31 стр.

 9. What is the role of software in a DBMS?
10. What are the advantages of organizing a database according to a relational
   model as opposed to a network model?
6. Discussion:
1. Using current publications, research the use of SQL. What do you think the
  future holds for it? What is it being used for? On what types of computers is
  it being used? How does SQL affect the way data can be used in business?
7. Essays:
Write a short report to explain the popularity of IBM's relational database
management system called DB2. Why has it been receiving so much attention?
What types of computers is it being used on? What types of companies are
investing in DB2 database management systems? What do you think the future
holds for DB2?

                                    UNIT 10
                            DATA COMMUNICATIONS
With the development of modern telecommunications and electronic
communications, business users and decision makers have been able to retrieve
and send data quickly to and from widely scattered sources through the use of
computers and communications hardware, software, and media.
    To understand the basics of electronic data communications, one must know
something about the characteristics of data transmission. When people speak,
the sound travels as analog signals — continuous signals that repeat a certain
number of times over a certain period (frequency) at certain amplitudes
(degrees of loudness). Telephone lines carry analog signals. Computers, in
contrast, use digital signals—discrete pulses of electricity (on) separated by
pauses (off).
    When they communicate, the sending and receiving computers must use
modems (modulate/demodulate) to convert the digital signals into analog
signals for transmission and then back again into digital signals for reception.
Modems can be acoustic couplers (into which the telephone headset is placed),
internal direct-connect (built into the computer or inserted on an add-on card
or board), or external direct-connect (connected to the computer and the
telephone by cable). Acoustic couplers are no longer commonly used.
    When signals are transmitted from computer to computer, patterns of bits
coded to represent data are sent one bit at a time. For the receiving computer
to be able to determine where one character of data ends and another starts,
data is sent either asynchronously or synchronously. In asynchronous
transmission, each string of bits that make up a character is bracketed by
control bits — a start bit, one or two stop bits, and an error check bit, or parity
bit. Most microcomputers use asynchronous transmission.
    In synchronous transmission, characters are sent as blocks with flags
inserted as identifiers at the beginning and end of the blocks. This type of