SYSTEM UNIT
- also known as system chassis
- contains electronic components that make up a computer system
Basis categories of system units
ELECTRONIC DATA AND INSTRUCTIONS
- Data and instructions are represented electronically
- Two-state or binary system is used to represent data and instructions
· BS consists of only two digits- 0 and 1
· Bit = short for binary digit
· Bytes = bits are combined into group of eight
- Three types of binary coding schemes
· ASCII - American Standard Code for Information Interchange
· EBCDIC - Extended Binary Coded Decimal Interchange Code
· Unicode– handles languages with large numbers of characters
SYSTEM BOARD
- Connects all components
- Allows communication between devices
- Main board or motherboard
- Circuit boardelectronic components
· Sockets
· Slots
· Bus lines
MICROPROCESSOR
- Central Processing Unit (CPU)
- Two Basic Components
· Control unit
· Arithmetic-logic unit (ALU)
Microprocessor Chips
- Chip capacities are expressed in word sizes
- Two Recent Significant Developments
· 64-bit processors
~ Have become standard for most of today’s desktop and laptop computers
· Multi-Core Chips
~ Can provide two separate and independent CPUs
~ Parallel processing
Specialty Processors
- Coprocessors
· Designed to improve specific computing operations
· Graphics coprocessors
- Smart cards
· Credit card sized with an embedded chip
· Used by many universities
- Specialty processors in cars
· As many as 70
· Used to control features
- RFID tags
· Information chips
· Used for tracking purposes
MEMORY
- Holding area for data, instructions, and information
- Memory is contained on chips connected to the system board
RAM
- Called VOLATILE STORAGE/TEMPORARY
· Their content will lose if power is disrupted
- Cache memory
· High-speed holding area for frequently useddata and information
- DIMM (dual in-line memory module)
· Used to expand memory
- Virtual memory
· Divides program into parts that are read inRAM as needed
ROM
- Read-only memory (ROM) chips are not volatile and cannot be changed by the user
- CPU can read, or retrieve data and programs but the computer cannot write
- Contain special instructions
· Needed to start a computer
· Give keyboard keys their special capabilities
· Put characters on screen
Flash Memory
- Flash memory offers a combination of the features of RAM and ROM.
- Flash memory is used for a wide of range of applications.
- If changes are made to the computer system, these changes are reflected in flash memory.
EXPANSION SLOTS AND CARDS
- Insert expansion cards into slot
- Ports on the card allow cables connect to devices outside the SU
- Types of EC:
· Graphics cards
· Sound cards
· Modem cards
· Network interface cards (NIC)
· PC cards and Express cards
· TV tuner- Allows you to view your favourite TV shows
BUS LINES
- Connect parts of the CPU to each other
- Data roadway for traveling bits
· Measured as bus width
· More lanes, faster traffic
- Two basic categories
· System buses
· Expansion buses
Expansion Buses
- Connects the CPU to other components on the system board, including expansion slots
- Principal types
· PCI Express (PCIe)
· Peripheral Component Interconnect (PCI)
· Universal serial bus (USB)
· FireWire buses
· Serial Advanced Technology Attachment (SATA)
PORTS
- Socket for connecting external devices
- Ports can connect directly to the system board or they can connect to cards that are inserted into slots on the system board
Standard Ports
- Four common ports
· VGA
· USB ports
· FireWire ports
· Ethernet ports
Legacy Ports
- Serial ports
- Parallel ports
- Keyboard and mouse ports
- Game ports
- Infrared data association (IrDA)
Specialized Ports
- Three specialized ports
· Musical Instrument digital interface (MIDI)
· Sony/Philips Digital Interconnect Format (S/PDIF)
· High Definition Multimedia Interface (HDMI)
Cables
- Used to connect exterior devices to the system unit via the ports
- One end of the cable is attached to the device and the other end has a connector that is attached to a matching connector on the port
POWER SUPPLY
- Computers require direct current (DC)
- DC power provided by converting alternating current (AC) from wall outlets or batteries
- Desktop computers use power supply units
- Notebooks and handhelds use AC adapters
Careers in IT
- Computer technicians repair and install computer components and systems
- Employers look for
· Certification in computer repair
· Good communication skills
- Continued education is required
- Computer technicians can expect to earn an hourly wage of $13.50 to $22.50
• References from
1. Computing Essentials Complete 2010 by Timothy J.O'Leary and Linda I.O'Leary from McGRAW Hill
2.http://en.wikipedia.org/wiki/Computer_case3.http://www.techterms.com/definition/system_unit
