Higher / Intermediate 2 Computer – Systems

1. Higher / Intermediate 2Computer – Systems Mr Climie Part 1

2. Data Representation • What you will learn here is how a computer that uses an odd number system called binary can still store all kinds of data such as numbers, text, sound or graphics.

3. Representing Numbers How We Change From Binary to Decimal

4. Why Computers Use Binary • Even if there is a slight drop in voltage it will still be detected as a 1 • There are only four rules for addition in binary compared to 100 in decimal [0+0=0 ; 0+1=1 ; 1+0=1; 1+1=10]

5. Binary to Decimal • We can change from our number system, decimal, to the computer number system, binary

6. Two’s Complement • Two's complement is the most popular method of working with negative binary numbers. • Do examples. H

7. Terms Used for Sizes 1Byte = 8 Bits 1KiloByte = 1024 bytes 1MegaByte = 1024 Kbytes 1GigaByte = 1024 Mbytes 1TeraBytes = 1024 GBytes

8. Representing Real Numbers • What you will learn here is how numbers with fractions, real numbers, are stored on computers. • You need to know the terms mantissa and exponent.

9. Mantissa and Exponent • A real number such as 612.987 can be rewritten as • 0.612987 x 103 • The 0.612987 is the mantissa • The power of 10, the 3, is the exponent

10. Real Numbers • Real numbers are stored by a group of connected bytes of memory. • It sets aside a few bytes for the mantissa and a few for the exponent.

11. Increase the Mantissa • If we increase the amount of storage for the mantissa we get a more accurate number stored, but we get a smaller range of numbers.

12. Increase the Exponent • If we increase the amount of storage for the exponent, we increase the range of numbers, but we decrease the accuracy.

13. Representing Text

14. Text Representation • In this section, you will find out how text is stored on computers and how we can guarantee that what you type is exactly what is printed out or sent to someone else.

15. Coding Text • When we type text into the computer, a numeric code is used to store it as a number.

16. ASCII • This was developed in the 1960’s • Due to peripherals being made by many different makers they needed a common code. • American Standard Code for Information Interchange became the common code.

17. ASCII Control Codes • Control codes can be used for device control such as cursor movement, page eject, or changing colours

18. Character Set • This is the set of characters that can be displayed. • If a different language is being used then a different character set may be used. • Examples could be • Latin set for English • Cyrillic for Russian • Chinese character set.

19. Problems With ASCII • It is American. • There is no code for the £. • There is not a code for European languages and the characters they use.

20. Unicode • This was designed to replace ASCII and have a unique numeric code for every written language. H

21. Advantage of Unicode • The advantage is guaranteed correct communication between • Countries • Peripherals H

22. ASCII or Unicode • ASCII files are smaller than Unicode files • Unicode has every possible character • ASCII is an 8-bit code • Unicode is a 16-bit code H

23. Representing Graphics

24. Representing Graphics • In this section you will find out how graphics are stored on computers. • There are a couple of methods in use and we discuss them.

25. Graphics Representation • The computer uses two methods to store a graphic on the computer. • Bit mapped • Records ever single dot or pixel used and stores the pixels directly in the computers memory. • Vector • Records how the diagram is made up by recording how we would draw the lines and shapes used in the diagram. H

26. Bit Mapped Graphics • The screen is drawn using dots called PIXELS. • Each pixel is connected directly to a set (map) of memory locations.

27. Bit Map Graphics and Colour • If we use colour, we need more than one bit of memory to record the pixel. • This is called bmp graphics. • A drawback is the very large size of file that can be produced by some pictures. • An advantage is we can edit individual pixels.

28. Bit Depth or Number of Colours • 2n is the amount of colours we can display when we use n bits to store the colours. • Sometime said as n-bit depth. • 8 – bit depth or 8 bit colour= 256 colours • 24 – bit colour (sometimes called true colour) H

29. Vector Graphics • This records ‘how’ to draw the shape by recording the ‘attributes’ of the shape. • A big advantage is it takes up very little space to record the picture. H

30. Example - Circle • A circle is drawn knowing the centre co-ordinates, the radius, and the colour of the circumference. • Circle1, 200,400, 15, red. H

31. Bit Mapped Picture Vector Graphic Picture

32. Graphic File Formats

33. Graphic File Formats • In this section you will find out the different ways graphic programs save their files. • No single program or format is the best, they all have different advantages, disadvantages and uses.

34. Graphic File Formats • Use the Internet to research the following graphic file formats • BMP • JPEG • Gif • Tiff • What it stands for • An advantage • A disadvantage • A likely use of each H

35. BMP • Bit Mapped Pictures • The standard format for Windows based computers. • It is a resolution-dependent file format. • A picture drawn on a screen of 800x600 pixel will look poor on a screen 1280x768 pixel • A drawback is the large file size • An advantage is being able to work at individual pixel level H

36. JPEG • JPEG is a format that uses compression. • This can lose data from an image. • If you save the compressed file again and again using the compression feature, you will lose detail over time. • JPEG files have the extension .Jpeg or .jpg • A major advantage is the file size, it is usually far smaller than BMP H

37. GIF • Graphic Interchange Format • Its resolution is low, it is designed for screen only use, making it unsuitable for printing purposes. • Animated GIF images are the most common method of creating a moving banner or animation for the web. H

38. TIFF • Tagged Image File Format • TIFF is a platform-independent format • The TIFF format was specifically designed for scanned images and use in DTP. • Uses bitmapped images • There are different versions in use, so it is not commonly used! H

39. Need for Compression • Graphic files can be very large. • Compression is used to make the file size smaller. • This may mean the picture loses some quality, but it is a more manageable size.

40. Memory Used By A Picture • In this section you will find out, by calculation, how much storage is required to store pictures.

41. Memory Used Calculation • We can calculate how much memory a picture will take up when stored. • There are two methods employed, it depends on whether it is displayed on a • Screen • Or • As a photograph

42. Photograph • When we scan a photo we need to know the scan resolution in dots per inch (dpi) and the number of colours or bit depth. • We can calculate the memory required to hold it as • Area of photo x dpi x dpi x bit depth

43. Monitor Screen • A computer screen uses resolution and bit depth only. • We need to know the screen size in pixels and the bit depth used. • Width in pixels times height in pixels times bit depth.

44. Examples

45. NOW WE LOOK AT SOFTWARE DEVELOPMENT

46. Computer Structure

47. Computer Structure • In this section you will find out some detail about the physical parts that make up a computer system. • The first part is the main central chip of the computer called the CPU.

48. Simple Diagram Processor Input Output Main Memory Backing Storage

49. ALU – Arithmetic Logic Unit • This is the part of the CPU where data is processed and manipulated. • The processing consists of • Arithmetical operations • Logical comparisons • It will also include registers to temporarily store the results of calculations.

50. Arithmetic Unit • Most computer calculations involve adding so a specialist arithmetic unit is part of the CPU. • 3 times 4 or 3x4 is 3 added together 4 times.