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

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

2 Systems 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 Systems 3 Representing Numbers How We Change From Binary to Decimal

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

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

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

8 Systems 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 Systems 9 Mantissa and Exponent A real number such as can be rewritten as x 10 3 The is the mantissa The power of 10, the 3, is the exponent

10 Systems 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 Systems 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 Systems 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 Systems 13 Representing Text

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

16 Systems 16 ASCII This was developed in the 1960s 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 Systems 17 ASCII Control Codes Control codes can be used for device control such as cursor movement, page eject, or changing colours

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

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

22 Systems 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 Systems 23 Representing Graphics

24 Systems 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 Systems 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 Systems 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 Systems 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 Systems 28 Bit Depth or Number of Colours 2 n 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 Systems 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 Systems 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 Systems 31 Bit Mapped Picture Vector Graphic Picture

32 Systems 32 Graphic File Formats

33 Systems 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 Systems 34 Graphic File Formats Use the Internet to research the following graphic file formats BMP JPEG Gif Tiff 1.What it stands for 2.An advantage 3.A disadvantage 4.A likely use of each H

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

41 Systems 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 Systems 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 Systems 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 Systems 44 Examples


46 Systems 46 Computer Structure

47 Systems 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 Systems 48 Simple Diagram Processor Main Memory Input Output Backing Storage

49 Systems 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 Systems 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.

51 Systems 51 Logic Unit This is special circuits designed to work out comparisons such as A 12 (Seats=yes) and (number < 6)

52 Systems 52 Control Unit This is the part of the CPU that manages the execution of instructions. It fetches each instruction in sequence Decodes the instruction Synchronises the commands Then executes the command This is done by sending out control signals to the other parts of the computer.

53 Systems 53 Registers These hold Data being processed Instructions being executed Addresses to be accessed

54 Systems 54 Internal Busses Higher Content Only

55 Systems 55 Internal Busses In this section you will find out how the various chips that make up the main section, or motherboard, of the computer can communicate between themselves.

56 Systems 56 What is a Computer Bus? A bus is a set of physical connections which are used by hardware components in order to communicate with one another. H

57 Systems 57 The Computer Busses There are three Address bus Data bus Control bus H

58 Systems 58 Address Bus This transports memory addresses which the processor wants to access in order to read or write data. The size of the address bus will determine how many memory locations can be addressed. The amount of memory accessible for a bus of width n is 2 n It is a unidirectional bus. H

59 Systems 59 Data Bus The data bus is used to transfer data either way between the memory and the CPU. It is a bi-directional bus H

60 Systems 60 Control Bus It sends signals to other parts of the computer to synchronise their tasks. It also transmits response signals from the hardware. It is a bidirectional bus. H

61 Systems 61 Example Control Lines Reset - to return a device back to its original state. Interrupt - the processor has to stop doing what it was doing and deal with this new more important task. Read – to initiate the transfer of data from the memory to the processor Write - to initiate the transfer of data from the processor to the memory. H

62 Systems 62 Fetch Execute Cycle The main task a computer does It gets an instruction that is stored in the memory of the computer, loads it into the cpu, then does the command it is set. This is called the fetch/execute cyle as it does this repeatedly many times per second.

63 Systems 63 Fetch Execute Cycle Setup address bus Enable read line Data transferred using data bus Command decoded Command executed H

64 Systems 64 Data Storage

65 Systems 65 Data Storage In this section you will get more details of how a computer stores the data it is using and storing. Also there is a common method used to speed up the access to that data.

66 Systems 66 Data Storage Computers make use of various styles of storage, they include: Main memory Cache Registers Backing storage

67 Systems 67 Main Memory There are two styles of memory in use RAM Random access memory is a type of computer storage whose contents can be accessed in any order ROM Read only memory is memory whose contents can be accessed and read but cannot be easily changed

68 Systems 68

69 Systems 69 Use of each type RAM holds the program and data in use at this moment. ROM will hold parts of the operating system we need when we start the computer.

70 Systems 70 RAM Random access memory The contents are lost when the power is off, this means it is volatile. It uses a system of unique memory locations to record where the data is stored.

71 Systems 71 ROM Read Only Memory ROM cannot be altered. Any software held in ROM is fixed during manufacture. Typical use is to store a basic set of operating system commands.

72 Systems 72 What comes next is mainly higher content, Int 2 pupils can investigate how RAM and ROM work.

73 Systems 73 Cache Memory –1 Cache memory is a relatively small amount (normally less than 1MB) of high speed memory that resides on the CPU H

74 Systems 74 Cache Memory – 2 Cache memory is designed to supply the CPU with the most frequently requested data and instructions. H

75 Systems 75 Backing Store Usually magnetic disks, storing data and programs. Backing store is cheaper but RAM is faster. Can also be re-writeable DVDs or CDs, called optical storage. H

76 Systems 76 Solid State Storage Device These devices are now very common, this is due to the capacity, physical size and robustness. They can store much more than cds and can match DVDs capacity of 5 Gbytes. H

77 Systems 77 Addressability The computer assigns numbers or addresses to physical memory locations on boot-up to keep track of the information that the CPU has access to. H

78 Systems 78 Memory Maps The O.S. Places into RAM a list of all the known, important locations. This is known as a memory map. Comparison of memory maps for different O.S. H

79 Systems 79 System Performance

80 Systems 80 How Fast Is That Computer? In this section you will find out how we can compare computers in terms of overall speed. We use terms such as powerful and fast but how do we compare them properly.

81 Systems 81 Clock Speed A computer's system clock resides on the motherboard. It sends out a signal to all other computer components in sync. Every action in the computer is timed by these clock cycles and takes a certain number of cycles to perform.

82 Systems 82 Clock Speed as System Performance This is only a basic measure. We can only compare them if they are made by the same company. Even then they must be from the same family of processors.

83 Systems 83 MIPS Millions of instructions per second. This measures how many simple instructions can be performed by the CPU in one second. MIPS measures CPU performance only, not the overall system performance.

84 Systems 84 Flops Floating point operations per second. This is similar to Mips but it uses real numbers with fractions in the calculations. Is still in use for modern computers.

85 Systems 85 How Do We Compare Computer Systems? Mips and Flops look at the processor on its own, but that does not take into account that some disc drives are much faster than others, so we need to be careful how we measure a computers speed. For a full comparison we use application tests which test many different programs and aspects of the whole system.

86 Systems 86 Application Based Tests A test that serves as a standard by which computer systems may be compared. This takes into account the complete computer system as well as software. Also known as benchmarks.

87 Systems 87 More Influences There are more methods of influencing how fast a computer works. These are in the way the computer is designed. On the next page you will learn of some of the ways this can be designed.

88 Systems 88 Factors That Affect System Performance Data bus width Wider the better Use of cache memory On board the CPU is better Rate of data transfer to and from peripherals Modern interfaces are much faster, USB2 is 40 times faster than USB1

89 Systems 89 Other Methods of Increasing System Speed Increasing clock speeds New parallel processors Increasing memory, 2 or 3 Gb Backing storage capacity1 Tb available

90 Systems 90 Peripherals

91 Systems 91 What Is a Peripheral? Peripherals may be internal or external. Examples of peripherals include printers, monitors, disk drives, scanners and so on. You will find out how we compensate for the difference in speed of the fast computer and the slow peripheral.

92 Systems 92 Peripheral list Item Mono laser Colour laser Inkjet printer DVD writerScanner Internal disc drive external disc drive tft monitor Details Resolution Capacity Speed Compatibility Name Cost

93 Systems 93 Practical Work The following few slides indicate the type of peripheral you are going to research. Write down the details as you find them. Note we want typical information NOT specific details of an actual peripheral.

94 Systems Typical Characteristics of Keyboard Mouse Microphone Touchpad

95 Systems Typical Characteristics of Digital camera Scanner Webcam

96 Systems Typical Characteristics of Monitor LCD panel Inkjet printer Laser printer Loudspeaker

97 Systems Typical Characteristics of Hard disc drive Magnetic tape drive CD-rom, CD-R, CD-RW DVD-rom, DVD-R, DVD-RW

98 Systems 98 Choice of Peripherals A peripheral is hardware that is added to a computer in order to expand its abilities. You can take in to account Resolution Capacity Speed of data transfer Compatibility Cost

99 Systems 99 Compensating for Speed Peripherals are slow in comparison to the computer There are methods employed to compensate for these speed differences. Buffers Spoolers

100 Systems 100 BUFFERS An amount of RAM on the peripheral, used for temporary storage of data that is waiting to be sent to a device, typically a printer. Used to compensate for differences in the rate of flow of data between components of a computer system.

101 Systems 101 Spoolers A method by which a disc drive can store data and feed it gradually to a printer, which is operating more slowly than the computer. More commonly used in a network.

102 Systems 102 Interfaces

103 Systems 103 Interfaces Interfaces are more than just a connector, the wrong choice can slow the speed of the computer system considerably, the right choice can speed it up. Most of the times you do not realise the interface is there, as it should be.

104 Systems 104 Purpose of an Interface Interfaces are used to pass data that are different in style but can be used by the equipment connected together by that interface.

105 Systems 105 Functions of an Interface Buffering Data format conversion Voltage conversion Protocol conversion Handling of status signals

106 Systems 106 Buffering This is when a section of RAM is set aside to store the data being transferred. It waits until a complete block of data is created, then transfers the data completely in one block. It then creates a new block of data.

107 Systems 107 Digital to Analogue Converter This converts digital signals into analogue signals.

108 Systems 108 Parallel to Serial Parallel All bytes of data sent at once in a row One cable per bit of data being sent Serial One bit sent at a time, one after the other down the same cable.

109 Systems 109 Voltage Conversion This may transform the mains AC to DC for the computer peripherals. It may convert the 240volts mains to the 5 volts the computer needs.

110 Systems 110 Interface Protocol A formal description of the rules and formats used to allow computer and peripheral to work properly together.

111 Systems 111 Status Registers There will be a special register on the interface that can communicate with the CPU. The status register could hold The printer is out of paper The disc drive is not ready The internet connection can not be made

112 Systems 112 Wireless This is becoming increasingly more and more common. There are two styles Bluetooth Wi-Fi

113 Systems 113 Wi-Fi It can let you use a printer in another room of the house. You can use peripherals up to quite a long distance away. (30m). You can share a Wi-Fi link with other users or make it secure.

114 Systems 114 Bluetooth This is also wireless but is much less powerful. It is designed to allow peripherals of any kind to communicate with others. It only works over about 10 metres distance or so. It is much slower than Wi-Fi.

115 Systems 115 Computer types A loose description of computer types is Embedded Palmtop Laptop Desktop Mainframe

116 Systems 116 Embedded These are incorporated into other devices, rather than being stand alone computers. Examples include digital cameras, mobile phones, music players and almost any kind of industrial or domestic control system

117 Systems 117 Palmtop The name for pocket computers of small size, low weight and long battery life. Its disadvantage, comparing to a PC, are reduced functions due to smaller memory and small screen. It is more intended for time planning, listing addresses and notes. Being replaced by Smart Phones such as the iPhone and similar.

118 Systems 118 Laptop A laptop is a computer that is characterized by mobility. Its components are similar to a desktop except miniaturized and made for low power consumption. Now being called a portable or notebook.

119 Systems 119 Desktop Designed to be used by one person only. The most commonly used style of computer. Easily upgraded and extended..

120 Systems 120 Mainframe A physically large computer which has an extensive amount of memory and disk space and is able to perform several different tasks simultaneously. It can have hundreds or even thousands of users connected to it.

121 Systems 121 Computer Task Can you compare the types of computer on Type of processor Speed of processor Size of main memory Backing storage Input and out put devices

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