Post on 27-Dec-2015
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System Units in MicrocomputersSystem Units (system cabinet):container that contain the electronic components of computer system
Types of System Units in Microcomputers
1. Desktop :input and output devices are located outside the system unit
2. Notebook(laptop): input devices located inside the system unit but output device like monitor is outside the system unit.
3. Tablet PC ,there are 2 kinds: 1-monitor is swivels and folds onto keyboard. 2-monitor is attached to system unit and does not have keyboard (supports the use of a stylus or pen to input commands and data )
4. Handheld (like ---PDA),input and output devices are inside system unit.
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Electronic Data and Instructions
Data and instructions are represented electronically
Computers recognize digital signals
Binary system (0,1)Bit
Byte
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Binary Coding Scheme
Two state systemOff/on electrical states
Characters represented by 0s and 1s
Three types of schemesASCII-used in microcomputer
EBCDIC-used in large computer
Unicode -16 bit code
Electronic components in system board:
1. Sockets (provide connection for chips)
2. Slots (provide connection point for cards)
3. Bus lines (provide communication paths)
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Microprocessor
Central Processing Unit (CPU )Two basic components 1. Control unit • Program instructions• Directs flow between memory and ALU• Directs flow between CPU and I/O devices
2. Arithmetic and logic unit
perform arithmetic and logical unit
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Microprocessor Chips
Chip capacities are expressed in word sizes
A word is the number of bits that can be accessed at one time by the CPU
byte=8 bits
32 bit –word----32/8=4-----this mean computer can accessv4 bytes at a time.
Dual-core microprocessor : It is chip can provide 2 separate and independent CPUs , so computer can run 2 programs at the same time.
Parallel processing :divide programs into parts so each CPU could process each part independently
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Memory
Holding area for data, instructions, and information
Types of memory chipsRAM (Random Access Memory)
ROM (Read Only Memory)
CMOS – flexible start-up instructions
Memory • RAM –temporary holding area,
-Volatile - when power shuts off, contents of RAM are lost.
• ROM – Read Only Memory; nonvolatile; user does not change information on ROM
- the factory put instructions and programs in ROM that that need to start computer
• CMOS – unlike RAM ,it is powered by battery
_unlike ROM ,data can be changed
_In CMOS information needed every time computer turned on like current data and time ,…
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Memory
Cache memory :high speed memory located between RAM and CPU ,computer make copy of most information accessed by CPU from RAM and put these information in Cache so results in faster processing results for the user
Flash memory :type of RAM hold data hold data even after computer turn off .It is expensive and used in digital camera and cell phone.
Virtual memory : divide large program into parts saved in hard disk then each part read into RAM when needed .
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System Clock
• Controls speed of systemProduces electrical beats
Expressed in gigahertz
Faster clock speed, faster computer
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Expansion Slots and Cards
Allow for new devices to be added
Plug & play : set of H.W & S.W , it can automatically install card.
Expansion cards are also called …Plug-in boards
Controller cards
Adapter cards
Interface cards
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Commonly Used Expansion Cards
Video cards
Modem cards
Network interface cards (NIC)
TV tuner cards
PC cards
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Bus Lines
Bus lines provide data pathways that connect various system components
bus width : the number of bits travel simultaneously
Two basic categories1. System buses
2. Expansion buses
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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
AC adapter
Power Supply Unit