COMPONENTSOF A

PERSONAL COMPUTER

A typical personal computer has

hard, floppy and CD-ROM disks

for storage, memory and CPU

chips inside the system unit, a

keyboard and mouse for input,

and a display, printer and

speakers for output.

The arrows represent the direction information flows

between the functional units.

Computer systems ranging from a

microcomputer to a large

supercomputer contain

components providing five

functions.

If you use a desktop

computer, you might already

know that there isn't any

single part called the

"computer.".

A computer is really a system of many parts working together. The physical parts, which you

can see and touch, are collectively called hardware.

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

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 isconnected to a circuit board called the motherboard.

Two main components of a motherboard are processor and memory.

SYSTEM UNIT?

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

Input Devices

Devices that bring

data INTO the

computer.

E.g. keyboard,

mouse,

microphone,

scanner and web

cam.

Output Devices

Devices that bring data OUT of the

computer.E.g. monitor,

speaker, printer

StorageDevices

Devices that is capable of STORING

information.

MOTHERBOARDThe 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

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.

PROCESSOR (CPU)?

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 single-core 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 1:

The controlunit fetches(gets) theinstruction

from memory.

STEP 2:

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.

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.

Registers

MEMORYMemory 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 devices2. Application programs that carry out a specific task such

as word processing3. The data being processed by the application programs

and resulting information.

TYPES OF MEMORYThe 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.

DRAM•requires constant refreshing or they lose their contents

•Volatile

•DRAM is used in main memory

MRAM

• stores data using magnetic charges instead of electrical charges

• 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