1. Chapter 4: Hardware for Educators
The System Unit

2. Learning Objectives
Define the term system unit and list its components.
Define the term mother board and list the components found on it.
Explain how data is represented in a computing device.
Explain what computer memory is and define the different types.
Explain what an expansion slot is in a desktop PC.

3. Learning Objectives
Explain what a port is and list the two most frequently use ports in a PC,
Explain what a bay is.
Explain what a power supply is.

4. The System Unit
The case that contains electronic components used to process data in a computer

5. The System Unit Common components of the system unit Mother Board
Ports
Drive Bays
Power Switch
Power Supply

6. Motherboard Main circuit board in the system unit which contains; CPU
Other IC’s
Expansion slots
Expansion cards
Memory slots
Memory cards
Ports

7. The Integrated Circuit
Integrated circuits contain many microscopic pathways capable of carrying electrical current

8. Data Representation
The basic building block of the CPU is the transistor. A CPU can contain billions of them.
Transistors can be only two electric charge states, + or -.
This creates the binary numbering system recognize two electronic states On and Off.
The binary numbering system uses two unique digits: 0 and 1, called bits (short for binary digits)

9. Data Representation
A bit by itself is not sufficient to produce useable information
Computers use bytes - made up of eight bits, this provides 256 different combinations of 1’s and 0’s to create usable information.
8-bit byte for the number 3
8-bit byte for the number 5
8-bit byte for the capital letter T

10. Data Representation
Coding schemes are use for data representation in computers, the two you will hear the most about are;
ASCII - American Standard Code for Information Interchange
Unicode - coding scheme capable of representing all world’s languages

11. Data Representation Converting to and from binary
Step 1. The user presses the capital letter D (shift+D key) on the keyboard.
Step 2. An electronic signal for the capital letter D is sent to the system unit.
Step 3. The signal for the capital letter D is converted to its Unicode binary code ( ) and is stored in memory for processing.
Step 4. After processing, the binary code for the capital letter D is converted to an image, and displayed on the output device.

12. How Components Interact In a PC
Instructions
Data
Information
CPU
Control Unit
Arithmetic Logic Unit
Input
Devices
Data
Output
Devices
Information
Memory
Instructions
Data
Information
Storage Devices

13. Central Processing Unit (CPU)
The two major components of the CPU are;
CPU
Control Unit
Arithmetic/ Logic Unit (ALU)

14. Systems Clock
The system clock on the mother board controls timing of all computer operations
This is the number used to measure how fast a CPU runs.

15. The System Unit - Cooling Systems
A great deal of heat is generated in the CPU and other components of the system unit
Types of cooling devices
Heat sink—component with fins that cools processor
Heat pipe—smaller device for notebook computers
Fans

16. Memory
Electronic components that store instructions, data, and information.
Consists of one or more chips or memory modules on motherboard
Each byte stored in unique location called an address, similar to seats on a passenger train
Memory is measured by the number of byte of storage available

17. Memory 512.000.000 bytes of memory (512 meg) X 8 bits in a byte =
4,096,000,000 transistors

18. Memory –Two Types nonvolatile memory volatile memory
Loses its contents when computer's power is turned off
nonvolatile memory
Does NOT lose its contents when computer’s power is turned off

19. Memory - RAM
Memory chips that can be read from and written to by processor
Also called main memory or primary storage
Most RAM is volatile, data it is lost when computer’s power is turned off
The more RAM a computer has, the faster it responds

20. Memory – Flash Memory Cards
Nonvolatile memory that can be erased electronically and reloaded
Used with PDAs, digital cameras, digital cellular phones, music players, digital voice recorders, printers, Internet receivers, and pagers
Allows users to transfer data from mobile devices to desktop computers
Hot plugging allows you to insert and remove cards while computer is running under Widows XP operating system

21. Memory – Read Only Memory (ROM)
Memory chips that store permanent data and instructions
Nonvolatile memory does not lose data when computer’s power is turned off

22. Expansion Slots and Cards
An expansion slot is a socket on the motherboard where a expansion card are inserted.
Expansion cards are used to improve the quality of the existing components on the mother board including
Video Cards
Audio Cards
Port Cards

23. Ports and Connectors USB Firewire
USB (universal serial bus) port can connect up to 127 different peripherals together with a single connector type
PCs typically have four to eight USB ports on front or back of the system unit
Firewire
Used to transfer video to computers

24. Bays
Open area inside system unit used to install additional equipment

25. Power Supplies Converts AC Power into DC Power
Fan keeps system unit components cool
External peripherals might use an AC adapter, which is an external power supply

26. Mobile Computing Devices
Include notebook, weighing between 2.5 and 8 pounds,
or mobile device such as a PDA