Bits and bytes

Computers can only manipulate 1 s and 0s in order to process information. A 1 is represented by current flowing through a wire and a 0 by no current flowing through the wire. Sometimes it is referred to as a high voltage and 0 is referred to as a low voltage. Everything about computers is based upon this binary process.

Each digit – 1 or 0 – is called a bit. Eight bits together are called a byte. The ASCII code is just a standard system to represent characters as bytes of binary signals.

ASCII, which stands for American Standard Code for Information Interchange, enables computers from different manufacturers to exchange data. ASCII uses 7-digit binary numbers to represent the letters of the alphabet, the numbers 0 to 9, various punctuation marks and symbols, and some special functions, such as the carriage return. Seven digits in binary implies that ASCII has room for 128 characters or symbols (with seven places to arrange 1s and 0s, we can make 128 possible code combinations). The eighth, or left-most bit of each byte, is often used to make sure the other seven bits are sent and received correctly (see the illustration). Some programmes use this bit for specific purposes.

When you press a key on the computer keyboard, your programme translates that key press into an ASCII code. This code can represent a character or a function to be performed.

ASCII codes are conventionally expressed in decimal notation because decimal numbers are more convenient for people to recognize and interpret than binary numbers.

In programming, it is also common to present binary codes by means of hexadecimal or octal notations. In hexadecimal notation, 16 is the base, or radix. The ten digits 0 to 9 are used, and in addition some more digits, usually A, B, C, D, E and F, to represent 10,11,12,13, 14 and 15 as single characters. Octal notation uses eight digits: 0, 1, 2, 3, 4, 5, 6, 7.

These notations are used to write software, as a shorthand way of representing long strings of bits. Thus the string 01000001 can be represented as octal 101, decimal 65 and hexadecimal 41.

Bits are also used to code pictures. The pixels displayed on the screen correspond to bits in the computer's video memory, held in the graphics adapter or video card. The local number of colours which can be shown on the screen depends on this graphics adapter, which converts the bits into visual signals.

Each pixel is a certain combination of the three primary colours: red, green and blue. A graphics adapter with 1 bitper primary colour can generate up to 8, or 2³ colours as you can see from the table below.

A graphics adapter with 8 bits per primary colour can generate 16.7 million or (2³) ⁸ colours.

Sources of information:

1. S. R. Esteras. Infotech English for Computer Users, 4^th edition (Student’s book, Teacher’s book, Workbook + audio) – Cambridge University Press, 2009. – 168pp.

2. S. R. Esteras, E. M. Fabre. Professional English in use: ICT – Cambridge

University Press, 2007. – 117 pp.

Vocabulary:

1) current – ток; electric current – электрический ток

2) high/low voltage – высокое/низкое электрическое напряжение

3) binary – двоичный

4) a bit – бит (наименьший элемент компьютерной памяти, имеющий два возможных состояния для хранения цифрового значения 0 или 1, что позволяет работать в двоичной системе счисления)

5) a byte – байт (единица измерения количества информации, равная 8 бит)

6) ASCII – American Standard Code for Information Interchange (американский стандартный код для обмена информацией – семиразрядный код для представления текстовой информации в компьютере, используется с отдельными модификациями в большинстве вычислительных систем)

7) to exchange data – обмениваться данными

8) a carriage – каретка (устройство, перемещающее печатающую головку принтера)

9) a carriage return – возврат каретки

10) a character – символ

11) to arrange – располагать в определённом порядке, последовательности, организовывать, классифицировать, систематизировать

12) to imply – предполагать, подразумевать, значить

13) room – место, пространство

14) the left-most bit – крайний левый бит

15) to make sure – убедиться

16) conventional – традиционный, общепринятый

17) in decimal notation – в десятичной системе счисления, в десятичной нотации (нотация – система обозначений, набор символов и правил для записи синтаксиса языка программирования)

18) to present binary codes by means of hexadecimal or octal notations – представлять двоичные коды с помощью шестнадцатеричной или восьмеричной систем счисления

19) a radix – основание системы счисления

20) a string – строка

21) to correspond to… – соответствовать чему-либо

22) a graphics adapter – графический адаптер, адаптер графических устройств

23) to convert bits into visual signals – конвертировать (преобразовывать) биты в визуальные (зрительные) сигналы

24) primary colours – основные цвета (группа цветов, из которых все остальные цвета могут быть получены путем смешивания)

25) a colour depth – глубина цвета

Exercises:

1. Complete the collocations:

1. high a) code

2. a graphics b) notation

3. decimal c) signal

4. an ASCII d) colour

5. a visual e) adapter

6. a primary f) voltage

II. Complete the sentences matching parts 1-10 to choices a-j:

1. A 1 is represented _____

2. Each digit – 1 or 0 – is called _____

3. Eight bits together are called _____

4. The ASCII code is ______

5. A 0 is represented _____

6. ASCII _______

7. ASCII uses 7-digit ______

8. Seven digits ______

9. The eighth, or left-most bit of each byte, is often used to make sure ____

10. ASCII codes are conventionally expressed _______

a) by current flowing through a wire.

b) in binary implies that ASCII has room for 128 characters or symbols.

c) the other seven bits are sent and received correctly.

d) by no current flowing through the wire.

e) a bit.

f) in decimal notation.

g) a standard system to represent characters as bytes of binary signals.

h) a byte.

i) enables computers from different manufacturers to exchange data.

j) binary numbers to represent the letters of the alphabet, the numbers 0 to 9, various punctuation marks and symbols, and some special functions.

III. Word building. Complete the table:

Noun	Verb	Adjective or participles	Adverb
			interchangeably
combination			-
	-	conventional
	add
	represent		-

IV. Complete the sentences using the correct derivative of the words from the table above:

1. ASCII, which stands for American Standard Code for Information _____________.

2. ASCII is a standard system of character ________________.

3. ASCII codes are ________________ expressed in decimal notation because it is more convenient for people to interpret them.

4. In hexadecimal notation six letters (A-F) are used in _____________ to ten digits (0-9) to represent 10, 11, 12, 13, 14 and 15 as single characters.

5. Primary colours can be ______________ to create up to 16.7 million colours.

V. Study the rules of reading numbers and formulae in English (see Appendix 1) and write down the numerals and mathematical expressions in words:

1. 16.7 million __________________________________________

2. 16,7 million __________________________________________

3. 0, 001_______________________________________________

4. 0.001 _______________________________________________

5._____________________________________________________

6. (2³) ⁸ ________________________________________________

7. _____________________________________________________

8. _____________________________________________________

9. _____________________________________________________

10. 45 % _______________________________________________

11. _____________________________________________________

12. 3_____________________________________________________

13. ____________________________________________________

14. ___________________________________________________

Дата добавления: 2014-10-31