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System Unit
Case that contains electronic components of the
computer used to process data
Made of plastic or metal and protects the internal
electronic components from damage
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Motherboard system board
Main circuit board of the system unit
Contains slots for adapter cards, processor chips andmemory
Adapter card: circuit boards that provide connections and
functions not build into the motherboard (sound card,video card)
Memory: holds data waiting to be processed andinstructions waiting to be executed
Computer chip: small piece of semiconducting material,usually silicon, on which integrated circuits are etched
Integrated circuit: contains many microscopic pathwayscapable of carrying electrical current; contains millions ofelements (resistors, capacitators, transistors)
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Processor
Central processing unit (CPU) Interprets and carries out the basic information
Impacts overall computing power
Manages most of the computers operations
On a personal computer: all functions of theprocessor are usually on a single chip
Microprocessor: personal computer processor chip
Processor core: contains the circuitry necessary toexecute instructions
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Control Unit
Directs and coordinate most of the operations in
the computer
traffic cop
Interprets each instruction issued by a program
Initiates the appropriate actions to carry the
instruction
Controls the internal components:arithmetic/logic unit and buses
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Arithmetic Logic Unit (ALU)
- performs arithmetic, comparison and otheroperations
Arithmetic Equations
- Basic calculations: addition, subtraction,multiplication, division
Comparison Equations
-Comparing one data item with another todetermine whether the first item is greaterthan, equal to, or less than the other item
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Machine Cycle
-For every instruction, a processor repeats a set offour basic operations
1. Fetching 2. Decoding
2. 3. Executing 4. Storing (if necessary) Fetching
process of obtaining a program instructionor data item from a memory
Decoding- process of translating the instruction intosignals the computer can execute
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Executing
- process of carrying out commands
Storing- writing the result to memory (not to a
storage medium)
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The System Clock
- A small quartz crystal circuit controls the timing
of all computer operations.
- Generates regular electronic pulses, or ticks that
set the pace of components of the system unit.
Clock speed - measure of the number of ticks per
second.
*current personal computers have clock speeds in the gigahertz range (one billion of
the system clock per second)
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* The faster the clock speed, the more
instructions the processor can execute per
second
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Comparison of Personal Computer
Processors
- Intel and AMD are the leading manufacturers
of personal computer processor chips.
- High-performance desktop personal
computers today use a processor in the Intel
Core family.
- Basic personal computers today use a brand of
Intel processor in the Pentium or Celeron
Family
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- Xeon and Itanium families of processors are
ideal for workstations and low-end servers.
- AMD is the leading manufacturer of Intel-
compatible processors
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Data Representation
- Only two discrete states: on and off
- Two digits, 0 and 1, easily can represent thesetwo states
- 0: off 1: on
Binary System
- a number system that has just two
unique digits, 0 and 1, called bits. Bit (binary digit)
-smallest unit of data the computer can
process
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Byte
- 8 bits grouped together
-provides enough different combinationsof 0s and 1s to represent 256 individual
characters (includes numbers, uppercase
and lowercase letters of the alphabet,
punctuation marks etc.)
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Memory
- Consists of electronic components that storeinstructions waiting to be executed by theprocessor.
- Consists of one or more chips on themotherboard or some other circuit board in thecomputer
- Stores 3 basic categories of items
1. The Operating System and other systemsoftware that control or maintain thecomputer and its devices
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2. Application programs that carry out a
specific task (such as word processing)
3. The data being processed by the
application programs and resulting
information
Stored program concept
- The role of memory to store both data
and programs
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Bytes and Addressable Memory
Byte
-basic storage unit in memory
-Each byte resides temporarily in a location
in memory that has an address Address
- is a unique number that identifies thelocation of the byte in memory
To access data or instructions in memory, thecomputer references the address that containsbytes of data.
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Memory Sizes
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TYPES OF MEMORY
2 types: (when the computers power is turnedoff)
Volatile memory
loses its contents
temporary
Nonvolatile memory does not lose its contents
Permanent
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VOLATILE MEMORY
RAM (Random Access Memory)
main memory
consists of memory chips that can be read from
and written to by the processor and other devices.
when the computers power is turned on, certain
operating system files load into the RAM from a
storage device such as the hard disk. These filesremain as long as there is continuous power in the
computer.
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3 basic types:
Dynamic RAM (DRAM; DEE-ram)- must be re-
energized constantly or they lose their contents. Static RAM (SRAM; ESS-ram)- faster and more
reliable than any variation of DRAM chips. Theydo not need to be re-energized as often asDRAM.
Magnetoresistive RAM (MRAM; EM-ram)-stores data using magnetic charges instead of
electrical charges. Manufacturers claim thatMRAM has greater storage capacity, consumesless power, and has faster access times thanelectronic RAM.
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Memory module- a small circuit board
Memory slots- hold memory modules and arefound on the motherboard.
RAM Configurations Amount of RAM necessary depends on what kind
of software you want to use
More RAM=faster computer Amount of RAM purchased today ranges from 1-
128 GB
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USER DESCRIPTION AMOUNT OF RAM
A (home) -Has latest version of
Windows-basic application
software
1GB of RAM
B (business) -work with
accounting, financial,and spreadsheet
programs
-also, programs with
multimedia
capabilities
2-8 GB of RAM
C -Creating professional
Web sites or graphic-
intensive applications 8 GB of RAM
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NONVOLATILE MEMORY
CACHE (cash)
Two Types: Disk cache
Memory cache it stores frequently used instructions two types:
L1 cache- built directly in the processor chip.
8KB-128 KB
L2 cache- slower but has a larger capacity than L1
64KB-16MB
Advanced transfer cache- 512 KB-12MB
L1 L2 RAM
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ROM (rahm) Read-only Memory
memory chips storing permanent data andinstructions
data in it cannot be modified
Firmware- ROM chips that contain permanent
written data, instructions, or information.
FLASH MEMORY can be erased electronically and rewritten
most computer use flash memory to hold their startupinstructions
on mobile computers and devices
Flash memory cardscontain flash memory on a
removable device instead of a chip
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CMOS (SEE-mos)
complimentary metal-oxide semiconductor
high speed and consumes little power
uses battery power
The flash memory chips that store a computers
startup information often use CMOS technology
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Memory Access Times
Access time- amount of time it takes a
processor to read data, instructions, and
information from memory.
accessing data on memory- 200,000 times
faster than accessing data on a hard disk
while access times of memory greatly affect
overall computer performance, manufacturers
and retailers usually list a computers memory
in terms of its size, not its access time.
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TERM ABBREVIATIO
N
SPEED
Millisecond ms One-
thousandth of
a second
Microsecond s One-millionth
of a second
Nanosecond ns One-billionth
of a second
Picosecond ps One-trillionth
of a second
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EXPANSION SLOTS AND ADAPTER
CARDSExpansion slot
a socket on the motherboard that can hold anadapter card
Adapter card
a circuit board that enhances functions of acomponent of the system unit and/or providesconnections to peripherals
Sometimes called an expansion card
Peripheral
a device that connects to the system unit and is controlledby the processor in the computer (e.g., modems, disk drives,printers, scanners, and keyboards)
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Some motherboards include all necessary capabilities and donot require adapter cards. Others may require adapter cards
to provide capabilities such as sound and video.
Sound card
enhances the sound-generating capabilities of apersonal computer by allowing sound to be inputthrough a microphone and output through externalspeakers or headphones.
Video card
also called graphics card; converts computer
output into a video signal that travels through a cableto the monitor, which displays an image on the screen
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Removable Flash Memory
Memory card
a removable flash memory device whichis inserted and removed from a slot in apersonal computer, game console, mobile
device, or card reader/writerusually no bigger than 1.5 in height orwidth
USB flash drive
a flash memory storage device that plugs ina USB port on a computer or mobile device
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Express Card slot
a special type of expansion slot that holds a PC Cardor an ExpressCard module
o PC Card
a thin, credit card-sized removable flashmemory device that primarily is used today
to enable traditional notebook computersand Tablet PCs to access the Internetwirelessly
o Express Card module
about one-half the size of a PC Card and adds
memory, communications, multimedia, andsecurity capabilities to computers
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Ports and Connectors
Port
the point at which a peripheral attachesto or communicates with a system unit so
that the peripheral can send data to orreceive information from the computer
sometimes called jack to identifyaudio and video ports
Connector
joins a cable to a port
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USB PORTSUSB portUniversal Serial Bus port
can connect up to 127 different peripheralstogether with a single connector
USB 2.0 or Hi-Speed USB
a more advanced and faster USB, with speeds 40 timeshigher than that of its predecessor
USB 3.0
even faster than USB 2.0
Both USB 2.0 and USB 3.0 are backward compatible, which means theysupport older USB devices as well as newer USB devices.
USB hub
a device that plugs in a USB port system unit and contains multipleUSB ports in which you plug cables from USB devices
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FIREWIRE PORTSFireWire port
previously called IEEE 1394 portSimilar to a USB port in that it can connect multiple
types of devices that require faster data transmission
speeds, such as digital video cameras, digital VCRs, color
printers, scanners, digital cameras, and DVD drives, to a
single connector
Allows you to connect up to 6 devices together
FireWire hub
used to attach multiple devices to a single FireWireport
A device that plugs in a FireWire port on the system
unit and contains multiple FireWire ports in which you
plug cables from FireWire devices
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OTHER PORTS
Bluetooth Port
Bluetooth technology uses radio waves to transmit databetween two devices given that they have to be within about33 feet of each other.
SCSI Port
a special high-speed parallel port which allows you to attachSCSI (/skuhzee/) peripherals such as disk drives and printers
o SAS (serial-attached SCSI) a newer type of SCSI thattransmits at much faster speeds than parallel SCSI
eSATA Port
external Serial Advanced Technology Attachment port
allows you to connect a high-speed external SATA hard disk toa computer
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IrDA Port
used by wireless devices to transmit signals to acomputer via infrared light waves
MIDI Port
Musical Instrument Digital Interface (/MID-dee/)
a special type of port that connects the system unit to amusical instrument, such as an electronic keyboard
O Synthesizer
creates sound from digital instructions;
can be a peripheral or a chip
A system unit with a MIDI port has the capability of recording
sounds that have been created by a synthesizer and then
processing the sounds (the data) to create new sounds.
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PORT APPLICATIONS AND DOCKING
STATIONS
Port replicator an external device that
provides connections to peripherals through
ports built into the device
Docking station an external device that
attaches to a mobile computer or device,
contains a power connection and providesconnections to peripheral
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Buses
Bus it allows the various devices both inside
and attached to the system unit to
communicate with each other
It consists of two parts:
data bus used to transfer actual data
address bus used to transfer information about
where the data should reside in memory
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Bus width size of a bus, it determines thenumber of bits that the computer can transmit atone time
A computer has three basic types of buses:
System bus or Front side bus (FSB) a part of themotherboard and connects the processor to mainmemory
Backside bus (BSB) it connects the processor tocache
Expansion bus it allows the processor tocommunicate with peripherals
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Bays
Bay an opening inside the system unit in
which one can install additional equipment
Drive bay a rectangular opening that typically
holds disk drives
External bay it allows a user to access openings
in the bay from outside the system unit
Internal bay concealed entirely within thesystem unit
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Power Supply
Power supply the component of the system
unit that converts the wall outlet AC power
into DC power
Wall outlets supply an alternating current (AC) of115 to 120 volts, and a computer requires a direct
current (DC) ranging from 5 to more than 15 volts
AC adapter an external power supply, it convertsthe AC power into DC power that the peripheral
requires
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K i Y C M bil
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Keeping Your Computer or Mobile
Device Clean
The system unit collects dust over time and
this can block airflow in a computer or mobile
device which can cause it to overheat, corrode
or even stop working.
So cleaning your computer or mobile device
once or twice a year will help it extend its life.
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It i t i f b i d t
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Its maintenance requires a few basic products: Can of compressed air removes dust and lint from
difficult-to-reach areas; removes sticky liquid spilled
on keyboards Lint-free antiseptic wipes and swabs
Screen cleaning solution or 50/50 mix of rubbingalcohol and water (do not use ammonia-basedsolutions)
Small computer vacuum Antistatic wristband to avoid damaging internal
components with static electricity
Small screwdriver - may be required to open the case
or remove adapter cards You can have a local professional or computer
company to clean the inside of your desktop ornotebook computer case for you.
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