Information and Creative Technology

Transcription

1 Information and Creative Technology Unit 2 Technology Systems Analogue and Digital data

2 Introduction Analogue data occurs in the natural world and changes constantly with time. Examples include the human voice, temperature and musical instruments. Digital data is a representation of a sequence of discrete values or numbers, such as digital clocks and Morse code. It is digital data that computers process in the form of binary numbers.

3 Analogue Digital Conversation There is a need to convert analogue signals, such as the human voice, to digital signals so that computers can process and interact with the natural world. Can you think of any?

4 Analogue Digital Conversation Digital transmissions are able to check for errors, so that there is no change or distortion in the data being transmitted. Sometimes computers encrypt digital transmissions to make them more secure, so if anyone is able to intercept the transmission they will not be able to understand the data. To transfer data it needs to be conveyed by either analogue or digital signals through cables or wireless. Data has to be converted to digital in order to be used by any devices or transferred over a network or the internet. Analogue data is data that continuously varies. An example of this is human speech: sound waves travel through the air and can be heard from someone s ears. Analogue data includes non-digital music and any sounds produced in the environment.

5 Analogue Analogue data travels in a wave. It is drawn in a smooth wave. This represents how sound waves move through the atmosphere. They are smooth and continuous with no breaks in them.

6 Digital Digital wave is data transmitted or stored using bits and bytes. The smooth analogue waves are sampled at regular intervals and simulate sound waves. Digital data is drawn in staggered waves. The computer fills in the gaps between the samples. The more often the waves are sampled, the higher the quality of the sound, as it is closer to the original analogue wave.

7 Binary Digital data in any computer is represented using binary notation. Which uses on two digits: 0 and 1. The use of binary notation works very well in every part of a computer, which is why binary numbers represent all data within a computer. Here are some examples of how binary notation is represented in different hardware devices. In RAM, binary notation is represented in transistors (electrical components contained within microprocessors) as with electrical charge (1) or without electrical charge (0). In hard disk drive, binary notation is represented in the magnetic surface of the disk as North (1) or South (0). In a DVD, binary notation is represented in the reflective surface of the disk to a laser as reflective (1) or not reflective (0).

8 Bits A bit (binary digit) is a single character of data, either a 1 or 0. It is the smallest measurement of data. Digital data is carried in pulses of energy around the components inside a digital device. Binary is represented by 1s and 0s, but is actually pulses of electricity which transfer data in a device. Pulse of electricity =1 No electricity = 0

9 ASCII American Standard Code for Information Interchange ASCII is a system used to represent characters in a binary format. It uses byte values to represent the numbers 0-9, byte Values to represent the upper case letters A-Z, Values to represent the lowercase letters a-z and other byte values for punctuation and other uses. You can see the ASCII character set used on a PC in the Character Map program in accessories under System Tools.

10 ASCII Table

11 Word and Word Length A word is a term to describe a number of bits for example, 32 bits used by a particular processor. A word is basically a fixed sized group of bits (binary data) that is handled as a group by the instruction set and the CPU The size of the word length is important in the processor design, as it affects the processoring power of a computer. In general, the larger the word length the greater the processing power of the microprocessor and the more memory that can be addressed. For example, in a memory subsystem such as the data bus between CPU and RAM, the amount of data transferred in a clock cycle is typically a word. Therefore, the larger the word length the greater the amount of data that is transferred per clock cycle, so the greater the processing power of the computer.

12 Storage Units A byte is used to describe the size or capacity of memory and data storage. The table on the next slide gives the different multiples of bytes used to show the magnitude of the units. Because computers use binary, magnitudes are used as the approximate values, so a megabyte is 1,048,576 bytes but is thought of as a million.

13 Storage Units

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