COMPONENTS
OF A
PERSONAL
COMPUTER
Computer systems
ranging from a
microcomputer to a
large supercomputer
contain components
providing five
functions.
The arrows represent the
direction information flows
between the functional units.
Software, on the other hand,
refers to the instructions, or
programs, that tell the hardware
what to do
The main components of a Personal
Computer are:
• System Unit
• Peripheral Devices
• Input devices
• Output devices
• Storage devices
• Processor (CPU)
• Memory
• Motherboard
• Expansion cards & slots
• Power supply unit
What is
SYSTEM UNIT?
A system unit is a case containing the electronic
components of the computer that are used to
process data.
The circuitry of the system unit is part of or is
connected to a circuit board called the
motherboard.
Two main components of a motherboard are
processor and memory.
PERIPHERAL DEVICES
Technically, a computer need only be made up of a
CPU and some RAM.
But a computer like this would not be much
use to anybody – other devices need to be connected
to allow data to be passed in and out of the computer.
The general name for these extra devices is
‘peripheral devices’. They are usually categorised into
input devices, output devices and storage devices.
PERIPHERAL DEVICES
Output Devices
Storage
Devices
Devices that is
capable of STORING
information.
Devices that bring
data OUT of the
computer.
E.g. monitor,
speaker, printer
MOTHERBOARD
The motherboard serves to connect all of the parts of
a computer together. The CPU, memory, hard drives,
optical drives, video card, sound card and other ports
and expansion cards all connect to the motherboard
directly or via cables.
Motherboard is also known as mainboard, mobo
(abbreviation), system board, logic board.
MOTHERBOARD
What is a
PROCESSOR
(CPU)?
Also called the central processing unit (CPU), a
processor interprets and carries out the basic
instructions that operate a computer.
The processor impacts overall computing power
and manages most of a computer’s operations.
On a PC, all functions of the processor usually
are on a single chip.
Some computer and chip manufacturers use the
term microprocessor to refer to a personal
computer processor chip.
Most processor chip manufacturers now offer
multi-core processors.
A processor core contains circuitry necessary to
execute instructions. The OS views each
processor core as a separate processor.
A multi-core processor is a single chip with two or
more separate processor cores.
Two common multi-core processors are dual-core
and quad-core.
A dual-core processor is a chip that contains two
separate processor cores.
A quad-core processor is a chip with four separate
processor cores.
Each processor core on a multi-core processor
generally runs at a slower clock speed than a singlecore processor, but multi-core processors typically
increase overall performance
For example, although a dual-core processor does not
double the processing speed of a single-core
processor, it can approach those speeds.
The performance increase is especially noticeable
when
users
are
running
multiple
programs
simultaneously such as antivirus software, spyware
remover, email-program, media player and etc.
Multi-core processors also are more energy efficient
than separate multiple processors, requiring lower
levels or power consumption and emitting less heat in
the system unit.
A processor contains a control unit and arithmetic logic
unit (ALU). These two components work together to
perform processing operations.
Control Unit (CU)
The control unit is the component of the
processor that directs and coordinates most
of the operations in the computer.
The control unit has a role much like a traffic
cop – it interprets each instruction issued by a
program and then initiates the appropriate
action to carry out the instruction.
Arithmetic & Logic Unit (ALU)
Arithmetic logic unit (ALU) is another component of
the processor that performs arithmetic, comparison
and logical operations.
Arithmetic operations include basic calculations
such as addition, subtraction, multiplication and
division.
Comparison operations involve comparing one data
item with another to determine whether the first item
is greater than, equal to or less than the other item.
Logical involves operations such as AND, OR, NOT.
How the CPU Executes Program
Instructions?
Before an instruction can be executed, program instructions
and data must be placed into memory from an input device
or a secondary storage device. Once the necessary data and
instruction are in memory, the central processing unit
performs the following FOUR steps for each instruction:
STEP 2:
STEP 1:
The control
unit fetches
(gets) the
instruction
from memory.
The control unit
decodes the
instruction (decodes
what it means) and
directs the
necessary data to be
moved from memory
to the ALU.
STEP 3:
The ALU executes
the arithmetic or
logical instruction.
That is, the ALU is
given control and
performs the actual
operation on the
data.
STEP 4:
The ALU stores the
result of this
operation in
memory or in a
register.
STEP 1 & STEP 2 together are called
instruction time, or I-time.
STEP 3 & STEP 4 together are called
Execution time, or E-time.
Registers
A processor contains small, high-speed storage locations
called registers that temporarily hold instructions or data.
Registers are part of the processor. They are NOT a part
of memory or a permanent storage device.
Processors have many different types of registers each
with a specific storage functions.
Register functions include storing the location from where
an instruction was fetched, storing an instruction while
the CU decodes it and storing the results of a calculation.
MEMORY
Memory consists of electronic components that store
instructions waiting to be executed by the processor, data
needed by those instructions and the results of processing
the data (information). Memory usually consists of one or
more chips on the motherboard or some other circuit board in
the computer.
Memory stores three basic categories of items:
1. The operating system and other system software that
control or maintain the computer and its devices
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.
TYPES OF MEMORY
The system unit contains two types of memory: volatile and
nonvolatile.
When the computer’s power is turned off, volatile memory
loses its contents. Volatile memory is temporary. Example is
RAM.
Nonvolatile memory does not lose its contents when power
is removed from the computer. Nonvolatile memory is
permanent. Examples are ROM, flash memory and CMOS.
RAM (RANDOM ACCESS MEMORY)
Random-access, commonly known as RAM or main
memory, consists of memory
RAM is volatile; data stored in RAM stays there
only as long as the computer is running. As
soon as the computer is switched off, the data
stored in RAM disappears.
RAM (RANDOM ACCESS MEMORY)
There are two different types of RAM:
1. DRAM (Dynamic Random Access Memory)
2. SRAM (Static Random Access Memory).
3. MRAM (Magnetoresistive Random Access Memory
SRAM
• faster and more
reliable than the more
common DRAM
• doesn't need to be
refreshed like dynamic
RAM.
• Volatile
• It is used primarily for
cache.
MRAM
DRAM
•requires constant
refreshing or they lose
their contents
• stores data using
magnetic charges
instead of electrical
charges
•Volatile
•DRAM is used
in main
memory
• has greater storage
capacity, consumes
less power, has faster
access times
MRAM
• Retain its
contents after
power is switch
off
RAM (RANDOM ACCESS MEMORY)
CACHE
Most of today’s computers improve their processing
times with cache.
Two types of cache are memory cache and disk cache.
Memory cache helps speed the processes of the
computer because it stores frequently used instructions
and data.
Most PCs today have two types of memory cache:
•L1 cache
•L2 cache
Some also have L3 cache.
CACHE
L1 CACHE:
• L1 cache is built directly in the processor chip.
• It usually has a very small capacity, ranging from 8KB
to 128KB.
L2 CACHE:
• L2 cache is slightly lower than L1 cache but has a
much larger capacity ranging from 64 KB to 16 MB.
• When discussing cache, most users are referring to
L2 cache.
ROM (READ ONLY MEMORY)
Read-Only Memory (ROM) is an integrated-circuit
memory chip that contains configuration data.
ROM is used in most computers to hold a small,
special piece of software: the 'boot up' program.
This software runs when the computer is switched on
or 'boots up'. The software checks the computer’s
hardware and then loads the operating system.
ROM (READ ONLY MEMORY)
Data stored in ROM is nonvolatile - it is not lost when
your computer is turned off.
Data stored in ROM is either unchangeable or
requires a special operation to change.
Examples of ROM are: Programmable ROM (PROM),
Erasable Programmable ROM (EPROM) and
Electrically Erasable Programmable ROM
(EEPROM).
FLASH MEMORY
Flash memory is a type of nonvolatile memory that
can be erased electronically and rewritten.
Most computers use flash memory to hold their
startup instructions because it allows the computer
easily to update its contents.
Example, when the computer changes from
standard time to daylight savings time, the contents
of a flash memory chip change to reflect the new
time.
FLASH MEMORY
Flash memory chips also store data and programs
on many mobile computers and devices such as
smart phones, portable media players, PDAs,
printers, digital cameras, etc.
CMOS
Some RAM chips, flash memory chips and other
memory chips use complementary metal-oxide
semiconductor (CMOS) technology because it
provides high speeds and consumes little power.
CMOS technology uses battery power to retain
information even when the power of the computer is
off.
The flash memory chips that store a computer’s
startup information often use CMOS technology.
EXPANSION SLOTS & ADAPTER CARDS
An expansion slot is a socket on the motherboard
that can hold an adapter card.
An adapter card sometimes called an expansion
card is a circuit board that enhances the functions
of a component of the system unit and/or provides
connections to peripherals.
EXPANSION SLOTS & ADAPTER CARDS
An expansion slot is a socket on the motherboard Some
motherboards include all necessary capabilities and do not
require adapter cards.
Other motherboards may require adapter cards provide to
provide capabilities such as sound and video.
A sound card enhances the sound-generating capabilities of a
PC by allowing sound to be input through a microphone and
output through speakers.
A video card also called a graphics card, converts computer
output into a video signal that travels through a cable to the
monitor which displays an image on the screen.
EXPANSION SLOTS & ADAPTER CARDS
Today’s computers support Plug and Play meaning the
computer automatically can configure adapter cards and
other peripherals as user install them.
Plug and Play support means user can plug in a device, turn
on the computer and immediately begin using the device.
PORTS & CONNECTORS
A port is the point at
which a peripheral
attaches to or
communicates with a
system unit so that the
peripheral can send data
to or receive information
from the computer.
A connector joins a cable
to a port. A connector at
one end of a cable
attaches to a port on the
system unit and a
connector at the other
end of the cable attaches
to a port on the
peripheral.
PORTS & CONNECTORS
Most connectors and ports are available in one of two
genders: male or female.
Male connectors and ports have one or more exposed pins
like the end of an electrical cord you plug in the wall.
Female connectors and cords have matching holes to accept
the pins on a male connector or port, like an electrical
outlet.
PORTS & CONNECTORS
Sometimes a new peripheral cannot be attach to the
computer because the port on the system unit is the
same gender as the connector on the cable. In this
case, purchasing a gender changer solves this
problem.
A gender changer is a device that enables you to
join a port and a connector that are both female or
both male.
USB PORTS
USB (Universal serial bus) port, can connect up to
127 different peripherals together with a single
connector.
Devices that connect to a USB port include the
following: mouse, printer, scanner, speakers,
portable media player, PDA, game console, etc.
PCs typically have six to eight USB ports on the
front and/or back of the system unit
USB PORTS
USB 2.0 also called Hi-Speed USB is more advanced
and faster with speeds 40 times higher than that of
its predecessor.
USB 3.0 is more than 10 times faster than USB 2.0.
FireWire PORTS
Similar to USB port in that it can connect multiple
types of devices that require faster data
transmission speeds such as digital video cameras,
scanner, digital cameras and DVD drives to a single
connector.
A FireWire port allows user to connect up to 63
devices together.
BUSES
A computer processes and stores data as a series
of electronic bits.
These bits transfer internally within the circuitry of
the computer along electrical channels.
Each channel, called a bus, allows the various
devices both inside and attached to the system unit
to communicate with each other.
Just as vehicles travel on a highway to move from
one destination to another, bits travel on a bus.
Buses are used to transfer bits from input devices to
memory, from memory to the processor, from
processor to memory and from memory to output or
storage devices.
Buses consist of three parts: a data bus and an
address bus.
Data bus - used to transfer actual data
Address bus – used to transfer information about
where the data should reside in memory.
Control bus – used to communicate with components
inside a computer to indicate whether the operation is
a read or a write.
The size of a bus called the bus width, determines the
number of bits that the computer can transmit at one time.
Example, a 32-bit bus can transmit 32 bits (4 bytes) at a
time.
The larger the number of bits handled by the bus, the faster
the computer transfers data.
If a number in memory occupies 64 bits, the computer must
transmit it in two separate steps when using a 32-bit bus:
once for the first 32-bit and once for the second 32-bit.
Using a 64-bit bus, the computer can transmit the number
in a single step, transferring all 64 bits at once. The wider
the bus, the fewer number of transfer steps required and
the faster the transfer of data.
EXPANSION BUS
Some peripherals outside the system unit connect to a port
on an adapter card which is inserted in an expansion slot
on the motherboard.
This expansion slot connects to the expansion bus which
allows the processor to communicate with the peripheral
attached to the adapter card.
The types of expansion buses on a motherboard determine
the types of cards user can add to the computer.
Expansion buses commonly found in today’s PCs: PCI bus,
PCI Express bus, AGP bus, USB, FireWire bus.
PCI (Peripheral Component Interconnect) bus
• a high-speed expansion that connects higher speed
devices.
• types of cards user can insert in a PCI bus expansion slot
include video cards, sound cards
PCIe (PCI Express) bus
• an expansion bus than expands on and doubles the speed
of the original PCI bus.
• Nearly all video cards today use the PCI Express bus, as
well as many hard disks and network cards
AGP (Accelerated Graphics Port) bus
• a bus designed by Intel to improve the speed with which
3D graphics and video transmit.
• with an AGP video card in an AGP bus slot, the AGP bus
provides a faster, dedicated interface between the video
card and memory.
• Newer processors support AGP technology.
USB bus & FireWire bus
• buses that eliminate the need to install cards in expansion
slots.
MODERN DAY APPLICATIONS OF
COMPUTER SYSTEMS
• Education
• Finance
• Government
• Health care
• Science
• Publishing
• Travel
• Manufacturing