C OMPUTING E SSENTIALS Presentations by: Fred Bounds Timothy J. O’Leary Linda I. O’Leary

3 3 The System Unit CHAPTER

3 Computing Essentials Chapter Three Competencies After reading this chapter, you should be able to: 1. Describe how a computer uses binary codes to represent data in electrical form. 2. Discuss each of the major system unit components. 3. Explain the differences among the three types of memory.

4 Computing Essentials Chapter Three Competencies 4. Discuss the two principal types of bus lines. 5. Discuss four widely used ports.

5 Computing Essentials Chapter Three Overview Understanding how application programs are executed Relative computing power based on speed, capacity and flexibility System unit basically a collection of electronic circuitry Knowing some basic principles will help users determine what kind of system will meet their needs

How Data and Instructions Are Represented Electronically They are represented as a binary, or two-state numbering system. The three principal binary coding schemes are ASCII, EBCDIC and UNICODE.

7 Computing Essentials Chapter Three Binary Representation The system unit can only work with data and instructions that have been converted to a binary form The binary digits or bits, are represented by the “off” position for zero, and the “on” position for one Eight bits combine to form a byte, roughly equivalent to a character

8 Computing Essentials Chapter Three Binary Coding Schemes Three popular ways of representing characters in binary form –ASCII (pronounced “as-key”) or American Standard Code for Information Interchange, is the most widely used

9 Computing Essentials Chapter Three Binary Coding Schemes Three popular ways of representing characters in binary form –EBCDIC (pronounced “eb-see-dick”) stands for Extended Binary Coded Decimal Interchange Code, IBM created for large computer systems –UNICODE - sixteen-bit code to support international languages

10 Computing Essentials Chapter Three How the letter is represented in ASCII code. Binary Coding Schemes Pressing a key converts character to a series of electronic pulses

11 Computing Essentials Chapter Three Binary Codes ASCIImicrocomputers Unicodeinternational languages

12 Computing Essentials Chapter Three ASCII and EBCDIC Codes

System Board The system board connects all system components and allows input and output devices to communicate with the system unit.

14 Computing Essentials Chapter Three System Board Also known as the main board and the motherboard Located in the system unit, a large flat circuit board with sockets and chips

15 Computing Essentials Chapter Three System Board Chips contain numerous circuits etched on a small wafer of layers of silicon and other materials

Microprocessor The CPU is located on the microprocessor chip and has two components - the control unit and the arithmetic and logic unit. RISC and CISC are two types of microprocessors.

17 Computing Essentials Chapter Three Control Unit Tells system how to carry out program instructions Directs electrical signal flow between memory and the arithmetic and logic unit Directs signal flow between the CPU and input and output devices

18 Computing Essentials Chapter Three Arithmetic-Logic Unit ALU for short Performs two types of operations –Arithmetic - fundamental math operations –Logical - one piece of data compared to another

19 Computing Essentials Chapter Three Microprocessor Chips Word size –Number of bits that may be simultaneously processed –Common way to express chip capacity –Size of word (e.g. 32 bit, 64 bit) determines power

20 Computing Essentials Chapter Three Microprocessor Chips CISC –“complex instruction set computer” –Most common form - e.g. Pentium RISC –“reduced instruction set computer” –use fewer instructions than CISC Smart cards - credit card size, with embedded microprocessor

Memory Three types of memory are RAM, ROM and CMOS.

22 Computing Essentials Chapter Three Memory RAMprograms and data CMOSflexible start-up instructions

23 Computing Essentials Chapter Three Temporarily holds data and programs being processed by the CPU Volatile - when power shuts off, contents of RAM are emptied Exception - flash RAM can retain data when power disrupted, but not widely used due to cost RAM

24 Computing Essentials Chapter Three Amount of RAM determines what and how many programs may be open at once and how much data can be generated Virtual memory facilitates the use of large programs by dividing them into parts and loading only certain portions into RAM as needed RAM

25 Computing Essentials Chapter Three RAM cache –Pronounced: “cash” –Area in RAM set aside to store information frequently accessed –Acts as a high speed, temporary holding area –Results in faster processing results RAM

26 Computing Essentials Chapter Three Memory Capacity ASCIImicrocomputers Unicodeinternational languages

27 Computing Essentials Chapter Three CMOS Complementary metal-oxide semiconductor Flexible and expandable memory Holds essential startup information on system components Supplied by battery, so non-volatile Unlike ROM, however, its contents may be updated

System Clock Speed of computer operations is measured in megahertz or millions of cycles per second.

29 Computing Essentials Chapter Three System Clock Controls speed and synchronizes operations inside the computer Expressed in megahertz, or millions of cycles per second Faster the clock speed, the faster the computer

Expansion Slots and Cards Expansion slots provide an open architecture. Expansion cards provide network connections, PC/TV combinations, and more.

31 Computing Essentials Chapter Three Expansion Slots and Cards This open architecture allows users to expand and update their systems Devices to meet these needs, expansion cards, are inserted into the expansion slots

32 Computing Essentials Chapter Three Expansion Slots and Cards Expansion cards also known as plug-in boards, controller cards, adapter cards or interface cards

33 Computing Essentials Chapter Three Expansion Slots and Cards Network adapter cards - connect system unit to a cable attached to a network Small computer system interface (SCSI, pronounced “scuzzy”) - in one slot, can support up to seven devices, such as CD-ROM, printers, hard drives

34 Computing Essentials Chapter Three Expansion Slots and Cards Television boards - TV tuner converts video signal for viewing on computer monitor

35 Computing Essentials Chapter Three Expansion Slots and Cards PC cards - credit card sized expansion cards for portable computers, also known as PCMCIA (Personal Computer Memory Card International Association) cards

36 Computing Essentials Chapter Three Expansion Slots and Cards After installing, system must be notified of the new board The relatively new “Plug and Play” development promises to make this task easier

Bus Lines Bus lines provide data pathways that connect various system components.

38 Computing Essentials Chapter Three Bus Lines Data roadway for travelling bits More lanes, faster traffic; 64 bit bus faster than a 32 bit

39 Computing Essentials Chapter Three Bus Lines Two major types –Industry Standard Architecture (ISA) - 16 bits, although slow, still widely used –Peripheral Component Interconnect (PCI) - a “local bus”, either 32 or 64 bit, more than twenty times faster than an ISA

Ports and Cables Ports are connecting sockets. Cables connect input and output devices to ports.

41 Computing Essentials Chapter Three Ports and Cables Connecting socket on the outside of the system unit Four common ports –Serial - data transported one bit at a time; mouse, keyboard, modem, etc. –Parallel - for external devices needing lots of data over short distances, like printers

42 Computing Essentials Chapter Three Ports and Cables Connecting socket on the outside of the system unit Four common ports –USB (universal serial bus) - can connect multiple devices; faster than parallel –FireWire - for speed printers and video cameras; faster than USB

43 Computing Essentials Chapter Three Cables Serial mouse, modem,keyboard Videomonitor

44 Computing Essentials Chapter Three System board Holds the various other system components Memory Holds programs and instructions Expansion Connect to network and other slots/boardssystem capabilities Ports Connect outside devices to system unit Major System Unit Components

45 Computing Essentials Chapter Three