Data representation
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This document provides an overview of how data is represented in computers using binary and bytes. It explains that all data, including integers, characters, pictures, sounds and computer programs, is broken down and stored as sequences of binary digits (bits) that represent the on/off states of switches. Bytes, which are 8 bits each, are used to store a single character, pixel, or other basic unit of different data types. The document includes examples of how integers, characters, images and sound waves are converted into and represented by bytes to be processed by the computer.
Data representation
- 1. Data in the Computer Presented by Mr.T.JohnsonPrince, M.Sc.(CS),B.Ed.(CS)
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- 4. Students should be able to learn: • Introduction • Representation of data in computer • Binary and switches • How data are stored in computer? • Integer, Character, Pictures, Sounds and Programs • Conclusion
- 5. Representing Data We have all seen computers do seemingly miraculous things with all kinds of sounds, pictures, graphics, numbers, and text. It seems that we can build a replica of parts of our world inside the computer. You might think that this amazing machine is also amazingly complicated - it really is not. In fact, all of the wonderful multi-media that we see on modern computers is all constructed from simple ON/OFF switches - millions of them - but really nothing much more complicated than a switch. The trick is to take all of the real-world sound, picture, number etc data that we want in the computer and convert it into the kind of data that can be represented in switches, as shown in Figure 1.
- 6. Figure 1: Representing Real-World Data In The Computer
- 7. Binary and Switches The computer has switches to represent data and switches have only two states: ON and OFF. Binary has two digits to do the counting: 0 and 1 - a natural fit to the two states of a switch (0 = OFF, 1 = ON).
- 8. Binary and Switches. • Bits and Bytes One binary digit (0 or 1) is referred to as a bit, which is short for binary digit. Thus, one bit can be implemented by one switch, as shown in Figure 2. 0 1 bit 1 1 bit 0110 4 bits 01101011 8 bits
- 9. Figure 3: Implementing a Byte Computer manufacturers express the capacity of memory and storage in terms of the number of bytes it can hold. The number of bytes can be expressed as kilobytes. Kilo represents 2 to the tenth power, or 1024. Kilobyte is abbreviated KB, or simply K. A kilobyte is 1024 bytes.
- 10. Representing Data in Bytes Here is an important thing to keep in mind: A single byte can represent many different kinds of data. What data it actually represents depends on how the computer uses the byte. Decibel a unit used to measure the intensity of a sound or the power level of an electrical signal by comparing it with a given level on a logarithmic scale.
- 11. Integers • Integers. Integer numbers are represented by counting in binary. • Integers are commonly stored using a word of memory, which is 4 bytes or 32 bits, so integers from 0 up to 4,294,967,295 (232 - 1) can be stored.
- 12. Characters • Characters. The computer also uses a single byte to represent a single character. But just what particular set of bits is equivalent to which character? In theory we could each make up our own definitions, declaring certain bit patterns to represent certain characters. • That is, there must be agreement on which groups of bits represent which characters.The code called ASCII (pronounced "AS-key"), which stands for American Standard Code for Information Interchange, uses 7 bits for each character.
- 13. Characters Figure 4: Character As a Byte Figure 5: Character Byte Stored In Memory
- 14. Picture and Graphic Data. • You have probably seen photographs that have been enlarged a lot, or shown close up - you can see that photographs are a big grid of colored dots. Computer graphic data like pictures, frames of a movie, drawings, or frames of an animation are represented by a grid of pixels. "Pixel" is short for picture element. In simple graphics (those without many colors), a byte can represent a single pixel. In a graphic representation called greyscale each pixel is a shade of grey from black at one extreme to white at the other.
- 15. Figure 6: Graphics as a Collection of Pixel Bytes
- 16. Sound Data As Bytes Sound occurs naturally as an analog wave, as shown in Figure 7. Most current electronic speakers, the means that we use to electronically reproduce sound, also produce analog waves. However, as we have seen, all data in the computer is digital and must be processed in bytes. The process of taking analog data, such as sound, and making it digital is called analog to digital conversion.
- 17. Figure 7. Sound Data As Bytes
- 18. Program Data as Bytes • Program Data as Bytes. When you buy a piece of software on a CD or diskette, you are getting a collection of instructions that someone wrote to tell the computer to perform the task that the software is meant to do. Each instruction is a byte, or a small collection of bytes.
- 19. Conclusion Data is represented in a computer by means of simple on/off switches, and digitally these become 1 and 0. Millions of switches in combination create all the data in a computer system.
- 20. Thank you