Identifying PC parts and their functions.
No : 23
Personal Computers (PCs) and PC-
based equipment are based on
Here we’ll examine common hardware
Visible to the end-user
Required for the PC to function
Case (we’ll look inside later)
The case is the “box” that holds the internal
components of the PC. It protects those
delicate components from dust and debris.
The monitor is the main output component
used on a PC. It’s where the computer is
able to show you what it, and you, are doing.
The keyboard is the main input device you
use with a computer or PC-based equipment.
On any PC that uses graphics (pictures), a
mouse is an essential input device that allows
you to control the PC.
Remember the case? We said it
contained internal components.
Internal components are the parts of the
computer that do most of the work,
though they are behind the scenes.
Understanding their basic functions is
important to understanding the PC as a
The motherboard (main board, system board)
is a large circuit board which all other PC
components connect to in some way.
There are many kinds of drives in a computer:
CDROM drives, hard drives, floppy drives, ZIP drives,
tape drives, pen drives. The basic function of all
drives is to store information (more on this later).
Random Access Memory (RAM) is memory that the
CPU uses when performing its tasks.
RAM consists of chips that plug into the motherboard.
In general, the more RAM you have, the better.
Expansion cards are circuit boards that
plug into the motherboard to expand its
capabilities. Sound cards are an
example. One required expansion card
is the video card, which connects to the
Normally an expansion card, but sometimes
built into the motherboard (integrated), the
video card has 15 holes, in three rows of five.
The power supply is crucial to the PC. It converts
power from the wall outlet into power the PC can use.
It powers all internal components, including the
motherboard and drives.
In industry, non-integrated PCs must
connect to external machines, such as:
– CNC machines
– Robotic devices
These connections are made via
Common communication ports are:
– Network Interface Card (NIC)
Barcode readers often attach to keyboard
Keyboard ports appear in DIN5 and PS/2 or
Some input devices connect via a mouse port.
Common mouse ports are PS/2 (Mini-DIN6) on the
left and serial (9 pin male) on the right.
Don’t connect a mouse-port device to a keyboard
Serial ports are fairly slow ports that can transmit
data over a long distance (hundreds of feet).
Serial ports are either 9 or 25 pin.
Serial ports are male (plugs) on the PC.
Parallel ports are normally used for output to
Parallel ports are 25 pin female (socket) on
Modems are normally expansion cards that
contain two phone jacks.
They communicate via phone lines to remote
Network Interface Card (NIC)
NICs are expansion cards that connect PC devices to
networks via special network cable.
Many connections to external machines are now
made via NICs, which normally have one port.
A popular technology to connect to external devices
is USB, which can support 127 devices.
USB will eventually replace keyboard, serial, and
Compare Communications Ports
Parallel is normally used for output only.
Keyboard and mouse ports are
normally input only.
Serial, NIC, Modem and USB are bi-
directional (input and output).
Storage is easiest to think of in terms of
primary and secondary.
Primary storage is used by the CPU.
The primary example is RAM. Primary
loses information without power.
Secondary devices can store data
without power. Drives are the main
secondary storage devices.
RAM stores information that is currently
Information in RAM must be saved to
secondary storage or it will be lost when
power is removed.
Secondary storage keeps data unless
the user removes it (or the device fails).
RAM vs. ROM
RAM stands for Random Access
RAM changes constantly as the CPU
needs different items in memory based
on the user’s requests.
RAM is lost when power is removed.
•ROM stands for Read Only Memory
•ROM does not change.
•ROM is not lost when the power is
removed from a PC.
•ROM stores key instructions that the
computer needs to boot up and operate.
Computer Hardware Components
– How did the computer become known as the
• Do they all have the same characteristics?
– Memory on chips and memory on magnetic
media, how do they differ?
– What do you look for when comparing memory
– How is information moved around within the
– How can you help your computer run better?
Basic Concepts of Computer
This model of the typical digital computer is often called the von
– Programs and data are stored in the same
memory: primary memory.
– The computer can only perform one instruction
at a time.
(Central Processing Unit)
Basic Concepts of Computer
Input/Output (I/O): Refers to the
process of getting information into and
out of the computer.
– Input: Those parts of the computer
receiving information to programs.
– Output: Those parts of the computer that
provide results of computation to the
person using the computer.
Sources of Data
for the Computer
Two types of data stored within a computer:
– Original data or information: Data being
introduced to a computing system for the first
• Computers can deal directly with printed text, pictures,
sound, and other common types of information.
– Previously stored data or information: Data
that has already been processed by a computer
and is being stored for later use.
• These are forms of binary data useful only to the
• Examples: Floppy disks, DVD disks, and music CDs.
Two categories of input hardware:
– Those that deal with original data.
– Those that handle previously stored data.
Input hardware: Those that deal with original data.
– Voice recognition hardware
– Digital camera
Digitizing: The process of taking a visual image, or
audio recording and converting it to a binary form for
– Used as data for programs to display, play or manipulate the
Connecting Hardware to the computer:
– Hardware needs access through some general
• Port: The pathway for data to go into and out of the
computer from external devices such as keyboards.
– There are many standard ports as well as custom
electronic ports designed for special purposes.
– Ports follow standards that define their use.
» SCSI, USB: Multiple peripheral devices (chain).
» RS-232, IDE: Individual peripheral devices.
• Peripheral device: A piece of hardware like a printer or
disk drive, that is outside the main computer.
Connecting Hardware to the computer:
– Hardware needs software on the computer
that can service the device.
• Device driver: Software addition to the
operating system that will allow the computer to
communicate with a particular device.
Common Basic Technologies for
Storing Binary Information:
– Most expensive of the three forms for
storing binary information.
– A flip-flop circuit has either one electronic
status or the other. It is said to flip-flop from
one to the other.
– Electronic circuits come in two forms:
– Two parts to most of the magnetic forms of
• The medium that stores the magnetic information.
– Example: Floppy disk. Tiny spots on the disk are
magnetized to represent 0s and 1s.
• The device that can “read” that information from the
– The drive spins the disk.
– It has a magnetic sensing arm that moves over the disk.
– Performs nondestructive reading.
– Uses lasers to “read” the binary information
from the medium, usually a disc.
• Millions of tiny holes are “burned” into the
surface of the disc.
• The holes are interpreted as 1s. The absence
of holes are interpreted as 0s.
Secondary Memory Input Devices
– These input devices are used by a
computer to store information and then to
retrieve that information as needed.
• External to the computer.
• Commonly consists of floppy disks, hard disk
drives, or CD-ROMs.
– Secondary memory uses binary.
• The usual measurement is the byte.
– A byte consists of 8 binary digits (bits). The byte is a
The four most important characteristics
of storage devices:
– Speed and access time
– Cost / Removable versus non-removable
– Type of access
Speed (Access time) - How fast
information can be taken from or stored
onto the computer memory device’s
– Electronic circuits: Fastest to access.
• 40 billionths of a second.
– Floppy disks: Very slow in comparison.
• Takes up to 1/2 second to reach full speed
before access is even possible.
– Megabyte: A Million bytes.
– Gigabyte: A billion bytes.
– Two parts to a removable secondary storage device:
• The cost of the medium. (Cheaper if bought in quantity)
• The cost of the drive.
Examples: Cost for drive Cost for medium
Floppy drive (1.4MB) 59.00 .50
Zip 100 (100 MB) 99.00 10.00
CD-WR (650 MB) 360.00 and up 1.00
Capacity - The amount of information that can be
stored on the medium.
Unit Description Approximate Size
1 bit 1 binary digit
1 nibble 4 bits
1 byte 8 bits 1 character
1 kilobyte 1,024 bytes ≈1/2 page, double spaced
1 megabyte 1,048,576 bytes ≈500,000 pages
1 million bytes
1 gigabyte 1,073,741,824 bytes ≈5 million pages
1 billion bytes
1 terabyte 1 trillion bytes ≈5 billion pages
Type of Access
• Sequential - Obtained by proceeding through
the storage medium from the beginning until
the designated area is reached (as in magnetic
• Random Access - Direct access (as in floppy
and hard disks).
Primary storage or memory: Is where the data and program that are
currently in operation or being accessed are stored during use.
– Consists of electronic circuits: Extremely fast and
– Two types:
• RAM (non-permanent)
– Programs and data can be stored here for the computer’s
– Volatile: All information will be lost once the computer
• ROM (permanent)
– Contents do not change.
The Central Processing Unit
The Central Processing Unit ( CPU)
– Often referred to as the “brain” of the computer.
– Responsible for controlling all activities of the
– The three major components of the CPU are:
1. Arithmetic Unit (Computations performed)
Accumulator (Results of computations kept here)
2. Control Unit (Has two locations where numbers are kept)
Instruction Register (Instruction placed here for analysis)
Program Counter (Which instruction will be performed next?)
3. Instruction Decoding Unit (Decodes the instruction)
– Motherboard: The place where most of the
electronics including the CPU are mounted.
Output units store and display information
(calculated results and other messages) for
us to see and use.
– Floppy disk drives and Hard disk drives.
– Display monitors: Hi-resolution monitors come in
• Cathode ray tube (CRT) - Streams of electrons make
phosphors glow on a large vacuum tube.
• Liquid crystal display (LCD) - A flat panel display that
uses crystals to let varying amounts of different colored
light to pass through it.
– Developed primarily for portable computers.
Audio Output Devices
– Windows machines need special audio card for
– Macintosh has audio playback built in.
– Audio output is useful for:
– CD player is a computer.
– Most personal computers have CD players that can access
both music CDs and CD-ROMs.
• Voice synthesis (becoming more human sounding.)
• Specialized tasks (i.e.: elevator’s floor announcements)
Optical Disks: CD-ROM and DVD
– CD-ROM (Compact Disk - Read Only Memory)
• By its definition, CD-ROM is Read Only.
• Special CD drives “burn” information into blank CDs.
– Burn: A laser is used to “burn” craters into the surface to
represent a binary 1.
– Two main types of CDs:
» CD-R (Compact Disk - Recordable)
» CD-WR (Compact Disk - ReWritable)
• It takes longer to write to a CD-R than a hard drive.
• Special software is needed to record.
DVD (Digital Versatile Disk)
– Allows up to 17 gigabytes of storage (from
4.7 GB to 17 GB).
– Compatible with older CD-ROM
– The four versions of the DVD:
Storage Requirements: How much storage
capacity is needed for…
– One keystroke on a keyboard. 1 byte (8 bits)
– One page single-spaced document. 4.0 K
– Nineteen pages formatted text. 75 K
– One second of high-fidelity sound. 95-110 K
– Complete word processing program. 8.4 MG
Storage Capacity: How much data can be
– One inch of 1/2 in. wide magnetic tape. 4 K
– One 3 1/2” floppy disk, high density. 1.4 MG
– One Compact Disk. 650 MG
– One DVD. up to 17 GB
Within the Computer
How do binary numerals move into, out of,
and within the computer?
– Information is moved about in bytes, or multiple
bytes called words.
• Words are the fundamental units of information.
• The number of bits per word may vary per computer.
• A word length for most large IBM computers is 32 bits:
Within the Computer
Bits that compose a word are
passed in parallel from place
– Ribbon cables:
• Consist of several wires,
• One wire for each bit of
the word or byte.
• Additional wires
coordinate the activity of
• Each wire sends
information in the form
of a voltage pulse.
Within the Computer
Example of sending
the word WOW over
the ribbon cable
ng to the
Packaging the Computer
The many physical forms of the
general purpose computer:
– All follow general
• Primary memory
• Input units
• Output units
• Central Processing Unit
– Grouped according to
speed, cost, size, and
Fast Expensive Complex Large
Slow Cheap Simple Small
Software Tools for Maintaining
Your Computer Hardware
Utility Programs exist that can help diagnose and solve computer
– Four major problem areas where utility programs
• Finding and fixing problems.
– Testing Input/Output peripherals.
– Testing RAM, motherboard, video cards.
– Recovering deleted files or fixing damaged disks.
• Improving computer performance.
– De-fragmenting a disk (Packs all files closer together).
• Preventative maintenance.
– Locates incompatible programs.
The PC consists of common external
and internal components.
Each component has a specific task.
Communication ports connect to
Storage devices are classified and
primary or secondary.