1. Living in a Digital World Discovering Computers 2010

2. The System Unit The system unit is a case that contains electronic components of the computer used to process data. 2

3. The System Unit The common components found inside the system unit includes: 3 Drive bay(s)Power supplySound cardVideo cardProcessorMemory

4. The System Unit The motherboard is the main circuit board of the system unit. – It connects all the components of the computer system. – Contains the processor, expansion slots, memory slots, and – Also called the system board. 4

5. The System Unit What is a chip? – A small piece of semi-conducting material on which integrated circuits are etched. Integrated circuits contain many microscopic pathways capable of carrying electrical current. – One of the most important chips in your computer is the processor chip. 5

6. Processor The processor interprets and carries out the basic instructions that operate a computer. – Also called the central processing unit (CPU). – The processor is made up of two components: 1.The control unit is the component of the processor that directs and coordinates most of the operations in the computer. 2.The arithmetic logic unit (ALU) performs arithmetic, comparison, and other logical operations. 6Processor Control Unit Arithmetic Logic Unit (ALU)

7. Processor 7

8. For every instruction, a processor repeats a set of four basic operations, which comprise a machine cycle. 8 Processor Control Unit Memory ALU Step 1. Fetch Obtain program instruction or data item from memory Step 2. Decode Translate instruction into commands Step 4. Store Write result to memory Step 3. Execute Carry out command

9. Processor What is pipelining? – A technique used by the processor to speed up processing of instructions. – Processor begins fetching a second instruction before it completes the machine cycle for the first instruction. – Results in faster processing. 9

10. Processor What is a register? – A temporary high-speed storage area, located on the processor, that holds data and instructions. 10 Stores location from where instruction was fetched Stores instruction while it is being decoded Stores data while ALU computes it Stores results of calculation

11. Processor What is the system clock? – Controls the timing of all computer operations. – Generates electronic pulses, or ticks, that set the pace for all components of the system unit and operations. – The pace of the system clock is called the clock speed or clock rate. Clock speed is currently measure in gigahertz (GHz). 11 1 GHz = one billion ticks of system clock per second 2 GHz = two billion ticks of system clock per second 3 GHz = three billion ticks of system clock per second

12. Processor What are dual-core and multi-core processors? – A dual-core processor is a single chip that contains two separate processors. – A multi-core processor is a single chip that contains two or more separate processors. 12

13. Processor The processor generates a lot of heat that can ruin the chip. Keeping things cool… – A heat sink is a component with fins that dissipates heat coming from the processor. – A heat pipe is a smaller device used for laptop computers. – Liquid cooling uses a continuous flow of fluids to transfer heat away from components. 13

14. Processor The leading manufacturers of processor chips are Intel and AMD. 14

15. Processor Parallel processing uses multiple processors simultaneously to execute a single program or task. – Massive parallel processing systems can involve hundreds or thousands of processors. 15

16. Data Representation Analog signals are continuous and vary in strength and quality Digital signals are in one of two states: on or off Most computers are digital. The binary system uses two unique digits (0 and 1) Bits and bytes 16

17. Analog Computers Analog computers were also made. – mechanical, hydraulic and electronic were the three types of analog computers. These computers were used for gun fire control systems. They had limitations, which is the reason digital computers are widely used today. All modern computers are digital. 17

18. Data Representation Most computers are digital. The binary system uses two unique digits (0 and 1) is used to represent data and instructions. – A bit is a binary digit, which is a single 1 or 0. 18 A computer circuit represents the 0 or the 1 electronically by the presence or absence of an electrical charge

19. Data Representation What is a byte? – Eight bits grouped together as a unit. – Provides enough different combinations of 0s and 1s to represent 256 individual characters. Numbers, letters, symbols, etc… 19

20. Data Representation ASCII (American Standard Code for Information Interchange) is the most widely used coding scheme to represent data 20

21. Data Representation 21 How is the letter T converted into binary form and back? Step 3. The system unit converts the scan code for the capital letter T to its ASCII binary code (01010100) and stores it in memory for processing. Step 2. An electronic signal for the capital letter T is sent to the system unit. Step 4. After processing, the binary code for the capital letter T is converted to an image, and displayed on the output device. T Step 1. The user presses the capital letter T (SHIFT+T key) on the keyboard.

22. Memory What is memory? – Electronic components that store instructions, data and the results. – Consists of one or more chips on the motherboard or other circuit board. – Each location in memory has an address. 22

23. Memory Memory size is measured by the number of bytes it can store. 23

24. Memory The system unit contains two types of memory: 24 Volatile memory Loses its contents when power is turned off Example includes RAM Nonvolatile memory Does not lose contents when power is removed Examples include ROM, flash memory, and CMOS

25. Memory 25 Step 1. When you start the computer, certain operating system files are loaded into RAM from the hard disk. The operating system displays the user interface on the screen. Operating system instructions Web browser instructions Paint program instructions Operating system interface Web browser window Paint program window Web browser program instructions are removed from RAM Web browser window is no longer displayed on desktop Step 2. When you start a Web browser, the program’s instructions are loaded into RAM from the hard disk. The Web browser window is displayed on the screen. Step 3. When you start a paint program, the program’s instructions are loaded into RAM from the hard disk. The paint program, along with the Web Browser and certain operating system instructions are in RAM. The paint program window is displayed on the screen. Step 4. When you quit a program, such as the Web browser, its program instructions are removed from RAM. The Web browser is no longer displayed on the screen. RAM

26. Memory Three basic types of RAM chips exist: 26 Dynamic RAM (DRAM) Static RAM (SRAM) Magnetoresistive RAM (MRAM)

27. Memory Where does memory reside? – RAM chips usually reside on a small circuit board called a memory module. – Memory slots on the motherboard hold memory modules. 27

28. Memory The amount of RAM necessary in a computer often depends on the types of software you plan to use 28 Page 226 Figure 4-21

29. Memory What is a memory cache? – Helps speed computer processes by storing frequently used data and instructions. 29  L1 cache built into processor  L2 cache slower but has larger capacity, built directly on processor chip  L3 cache is separate from processor chip on motherboard.

30. Memory Read-only memory (ROM) refers to memory chips that permanently store data and instructions Firmware A PROM (programmable read-only memory) chip is a blank ROM chip that can be written to permanently EEPROM can be erased 30

31. Memory What is Flash memory? – Non-volatile memory that can be erased electronically and rewritten. – Used with PDAs, smart phones, printers, digital cameras, automotive devices, etc... 31

32. Memory What is CMOS? 32 Uses battery power to retain information when other power is turned off Stores date, time, and computer’s startup information Complementary metal-oxide semiconductor memory Used in some RAM chips, flash memory chips, and other types of memory chips

33. Memory Access time is the amount of time it takes the processor to read items from memory. – Measured in nanoseconds (ns) – It takes 1/10 of a second to blink your eye; a computer can perform over 10 million operations in same amount of time. 33

34. Expansion Slots and Adapter Cards An expansion slot is a socket on the motherboard that can hold an adapter card An adapter card enhances functions of a component of the system unit and/or provides connections to peripherals – Sound card and video card 34

35. Expansion Slots and Adapter Cards With Plug and Play, the computer automatically can configure adapter cards and other peripherals as you install them 35

36. Expansion Slots and Adapter Cards Removable flash memory includes: – Memory cards, USB flash drives, and PC Cards/ExpressCard modules 36

37. Ports and Connectors A port is the point at which a peripheral attaches to or communicates with a system unit. A connector joins a cable to a port. 37

38. Ports and Connectors 38

39. Ports and Connectors On a notebook computer, the ports are on the back, front, and/or sides 39

40. Ports and Connectors 40

41. Ports and Connectors A USB port can connect up to 127 different peripherals together with a single connector. – You can attach multiple peripherals using a single USB port with a USB hub. 41

42. Ports and Connectors Other types of ports include: 42 Firewire port Bluetooth port SCSI port eSATA port IrDA portSerial portMIDI port

43. Ports and Connectors A Bluetooth wireless port adapter converts a USB port into a Bluetooth port A smart phone might communicate with a notebook computer using an IrDA port 43

44. Buses What is a bus? – Channels that allow all devices connected to the computer to communicate with each other. – The system bus connects the processor to RAM memory. – The bus width determines the number of bits that can be transmitted at one time. 44

45. Buses Expansion slots connect to expansion buses. Common types of expansion buses include: 45 PCI bus PCI Express bus Accelerated Graphics Port USB and FireWire bus PC Card bus

46. Bays A bay is an opening inside the system unit in which you can install additional equipment. – A drive bay typically holds disk drives. 46

47. Power Supply The power supply converts the wall outlet AC power into DC power Some external peripherals have an AC adapter, which is an external power supply 47

48. Quote of the Day Change is inevitable … Except from a vending machine. 48