Lecture 2 - Computer Hardware & Operating Systems

EDU-6403, Educational Hardware Systems
Jack A. Hyman, Ph.D

So what does an educational
hardware system consist of…
Components of an educational technology computing
infrastructure consist of software, data, and networks –
require computer hardware for their storage or operation.

The Computer System
Computer system consists of:
central processing unit (CPU)
primary storage
secondary storage
input devices
output devices
Communications devices.

Computer System Overview
Communication
Devices
Secondary
Storage
- Magnetic disk
Central
Processing Unit
(CPU)
Primary Storage
Input Devices
- Keyboard
Output Devices
- Printers
Buses

The System Unit
What are common components inside the system unit?
 Processor
 Memory
 Adapter cards
 Sound card
 Video card
 Ports
 Drive bays
 Power supply
power supply
ports
drive bays
processor
memory
sound cardvideo card

The System Unit
What is the motherboard?
 Main circuit board in
system unit
 Contains adapter
cards, processor
chips, and
memory chips

Core Computer Components
The CPU
manipulates raw data into more useful form and controls the
other parts of the computer system.
Primary storage
temporarily stores data and program instructions during
processing.
Secondary storage
devices store data and programs when they are not being
used in processing.

Device Types
Input devices
convert data and instructions into electronic form for input
into the computer.
Output devices
convert electronic data produced by the computer system
and display them in a form that people can understand.
Communication devices
provide connections between the computer and
communications networks.

The Computer Bus
Buses
are circuitry paths for transmitting data and signals
among the parts of the computer system.

How computers actually work
How is a letter converted to binary form and back?
Step 1.
The user presses
the capital letter D
(shift+D key) on
the keyboard.
Step 2.
An electronic signal for the
capital letter D is sent to the
system unit.
Step 3.
The signal for the capital letter D
is converted to its ASCII binary
code (01000100) and is stored in
memory for processing.
Step 4.
After processing, the binary
code for the capital letter D is
converted to an image, and
displayed on the output device.

The CPU and Primary Storage
The CPU is the part of the computer system where the
manipulation of symbols, numbers, and letters occurs, and it
controls the other parts of the computer system.
The CPU

Processor
Control
Unit
Arithmetic
Logic Unit (ALU)
Arithmetic
Logic Unit (ALU)
Processor
What is the central processing unit (CPU)?
Input
Devices
Storage
Devices
Output
Devices
 Interprets and carries out
basic instructions that
operate a computer
MemoryData Information
Instructions
Data
Information
Instructions
Data
Information
Control
Unit
 Control unit directs and
coordinates operations in
computer
 Arithmetic logic unit
(ALU) performs
arithmetic, comparison,
and logical operations
 Also called the processor

Processor
Control Unit
Memory
ALU
Processor
Step 1. Fetch
Obtain program instruction
or data item from memory
Step 2.
Decode
Translate
instruction into
commands
Step 4. Store
Write result to memory
Step 3. Execute
Carry out command
Four operations of the CPU comprise a machine cycle

Types of Buses
Three kinds of busses linked between the CPU, primary storage
and the other devices in the computer system:
Data bus
Pass information in bi-directional.
Address bus
Transmits signals for locating a given address in primary
storage, indicating where data should be placed.
Control bus
Transmits signal specifying whether to read or write data to
or from primary storage address, input device or output
device.

The Arithmetic-Logic Unit and
Control Unit
An arithmetic logic unit (ALU) and control unit is one of the core
components of all central processing units.
The ALU performs the computer’s principal logical and arithmetic
operations.
It adds, subtracts, multiples, and divides, determining whether a
number is positive, negative, or zero.

Primary Storage
Primary storage is a category of computer storage, often called
main memory.
Has three functions:
• Stores all or part of the program that is being executed.
• Stores the operating system programs that manage the
operation of the computer.
• Holds data that the program is using.
Data and program are placed in primary storage before processing,
between processing steps and after processing has ended prior to
being returned to secondary storage or released as output.

Memory
How is memory measured?
Kilobyte KB or K 1 thousand bytes
Megabyte MB 1 million bytes
Gigabyte GB 1 billion bytes
Terabyte TB 1 trillion bytes
By number of bytes available for storage

Types of Primary Storage
Modern primary storage devices include:
Random access memory (RAM)
is used for short-term storage of data or program
instructions. RAM is volatile. Its contents will be lost when
the computer’s electric supply is disrupted by a power
outage or when the computer turned off.
Read-only memory (ROM)
can only be read from. It cannot be written to. ROM chips
come from the manufacturer with programs already burned
in, or stored. ROM is used in general-purpose computers to
store important or frequently used programs, such as
computing routine for calculating the square roots of
numbers.

Memory
What is random access memory (RAM)?
The more RAM a
computer has, the
faster it responds
Also called
main memory
or primary
storage
Most RAM is
volatile, it is lost
when computer’s
power is
turned off
Memory chips that can be
read from and written
to by processor

Memory
How do program instructions transfer in and out of RAM?
Step 1. When you start the computer, certain
operating system files are loaded into RAM from
the hard disk. The operating system displays the
user interface on the screen.
Operating system
instructions
Web browser
instructions
Word processing
program instructions
Operating system
interface
Web browser
window
Word processing
program window
RAM
RAM
Web browser program
instructions are
removed from RAM
Web browser
window is no longer
displayed on
desktop
Step 2. When you start a Web browser, the
program’s instructions are loaded into RAM from
the hard disk. The Web browser window is
displayed on the screen.
Step 3. When you start a word processing
program, the program’s instructions are loaded
into RAM from the hard disk. The word
processing program, along with the Web Browser
and certain operating system instructions are in
RAM. The word processing program window is
displayed on the screen.
Step 4. When you quit a program, such as the
Web browser, its program instructions are
removed from RAM. The Web browser is no
longer displayed on the screen.

Must be
re-energized
constantly
Do not have to
be re-energized
as often as
DRAM
Most
common
type
Faster and
more reliable
than DRAM
chips
Memory
What are two basic types of RAM chips?
Static RAM
(SRAM)
Dynamic
RAM
(DRAM)

Memory
Read Only Memory
• Memory chips that store permanent data and instructions. This
memory is novalative.
• Nonvolatile memory, it is not lost when computer’s power is turned
off
Three Types
• Firmware - Manufactured with permanently written data,
instructions, or information
• PROM - (programmable read-only memory)— Blank ROM chip onto
which a programmer can write permanently
• EEPROM - (electrically erasable programmable read-only
memory)— Type of PROM containing microcode programmer can
erase

Storage, Input, and Output
Technology
Storage, input and output devices are called peripheral
devices because they are outside the main computer
system unit.

Secondary Storage Technology
• Secondary storage is used for relatively long term
storage of data outside the CPU.
• Secondary storage is nonvolatile and retains data
even when the computer is turned off.
• Magnetic disk, optical disk and magnetic tape are
examples of secondary storage.

Storage
What is storage?
• Holds data, instructions, and information for future use
Storage medium is physical material used for storage
• Also called secondary storage

Magnetic disk
There are two kinds of magnetic disk:
• floppy disks
• hard disks
• Magnetic Disks permit direct access to individual records so that
data stored on the disk can be directly accessed regardless of
the order in which the data were originally recorded.
• Disk storage is often referred to as a direct access storage
device (DASD).

Magnetic Disks
What is a hard disk?
• High-capacity storage
• Consists of several
inflexible, circular platters
that store items
electronically
• Components enclosed in
airtight, sealed case for
protection

Magnetic Disks
What are tracks and sectors?
Track
is narrow
recording band
that forms full
circle on disk
Sector
stores up
to
512 bytes
of data
Formatting prepares disk for use and marks bad sectors as unusable

Magnetic Disks
How does a hard disk work?
Step 1.
Circuit board controls
movement of head
actuator and a small
motor.
Step 2.
Small motor spins
platters while
computer is
running.
Step 3.
When software
requests a disk access,
read/write heads
determine current or
new location of data.
Step 4.
Head actuator positions
read/write head arms
over correct location on
platters to read or write
data.

Optical Disk
• Also called compact disks or laser optical disks, this
type of media uses laser technology to store data at
densities many times greater than those of magnetic
disks.
• The most common optical disk system used with PCs
called CD-ROM (compact disk read only memory).
CD-ROM is read-only storage.

Push the same button
to close the tray.
Optical Discs
What are optical discs?
• Most PCs include an optical
disc drive
• Flat, round, portable metal
discs made of metal,
plastic, and lacquer
• Can be read only or
read/write
Insert the disc,
label side up.
Push the button to
slide out the tray.

Optical Discs
How is data stored on an optical disc?
• Typically stored in single track
• Track divided into evenly
sized sectors that store
items
single track
spirals to edge
of disc disc sectors

Types of Optical Media
• WORM (write once/read memory) or CD-R (compact disk-
recordable) optical disk systems allow users to record data only
once on an optical disk.
• New CD-RW (CD-Rewritable) technology has been developed
to allow users to create rewritable optical disks.
• Digital-video disks (DVDs) also called digital versatile disks are
optical disks the same size as CD-ROMs but of even higher
capacity (minimum of 4.7 gigabytes of data).

Magnetic Tape
Magnetic tape is an older storage technology that still used for
secondary storage of large volumes of information.
The principle advantages
its inexpensiveness, its relative stability and its ability to store
very large quantities of information.
The disadvantages
its sequentially stored data and its relative slowness compared
to the speed of secondary storage media.

Tape
What is tape?
– Magnetically coated plastic ribbon capable of storing large
amounts of data at low cost
– Primarily used for backup

PC Cards
What is a PC Card?
• Adds capabilities to computer
• Credit-card-sized device commonly
used in notebook computers

Input and Output Devices
Input devices
Input devices gather data and convert them into electronic form for
use by the computer.
Keyboard
The principal method of data entry for entering text and
numerical data into a computer
Pointing Devices
A computer mouse is handheld device with point-and-click
capabilities that is usually connected to the computer by a cable.
Touch screens allows users to enter limited amounts of data by
touching the surface of a sensitized video display monitor with
finger or a pointer.

Capture Automation (I/O)
Source Data Automation
Captures data in computer-readable form at the time and place
they are created.
• Optical Character Recognition (OCR) devices translate
specially designed mark, characters, and codes into digital form.
• Magnetic ink character recognition (MICR) technology is
used primarily in check processing for the banking industry,
which the bottom of typical check contains characters identifying
the bank, checking account, and check number that are
preprinted using a special magnetic ink.

Capture Automation (I/O)
• A MICR reader translates these characters into digital form for the
computer.
• Handwriting-recognition devices such as pen-based tablets,
notebooks, and notepad are promising new input technologies.
• These pen-based input devices convert the motion made by an
electronic stylus pressing on a touch-sensitive tablet screen into
digital form.
• Digital scanners translate image such as pictures or documents
into digital form.
• Voice input devices convert spoken words into digital form for
processing by the computer.
• Sensors are devices collect data directly from the environment for
input into a computer system.

What Is Input?
What is input?
 Input device: Any hardware component that allows users to
enter data and instructions
 Data or instructions entered into memory of computer

What Is Input?
What are the two types of input?
• Unprocessed text,
numbers, images,
audio, and video
Instructions
• Programs
• Commands
• User responses
Data

The Keyboard
How is the keyboard divided?
• Typing area
• Numeric keypad
• Function keys, special
keys that issue
commands

Pointing Devices
What is a mouse?
• Pointing device that fits under palm of hand
 Pointing device controls
movement of pointer, also called
mouse pointer
 Mechanical mouse
has rubber or metal
ball on underside
mouse buttons
wheel
butto
n
mouse pad
ball

Other Pointing Devices
What is a touch screen?
• Touch areas of screen with finger
• Often used with kiosks

Video Input
What is video input?
• Process of entering full-motion images into computer
• Video capture card is adapter card
that converts analog video signal
into digital signal that computer
can use
• Digital video (DV) camera
records video as digital signals

Video Input
What are a PC video camera and a Web cam?
 PC video camera / recorder—cDV camera used to capture video
and still images, and to make video telephone calls on Internet
 Also called PC camera
 Web camera—video camera whose output displays on
a Web page (Skype)

Scanners and Reading Devices
What is a scanner?
• Light-sensing device that reads
printed text and graphics
• Used for image processing,
converting paper documents into
electronic images
Drum
Flatbed
Pen or
Handheld
Sheet-fed

How does a flatbed scanner work?
Step 2. Bright light moves underneath scanned document.
Step 3. Image of the document is reflected into a series of
mirrors.
Step 1. Document to be scanned is placed face down on the
glass window.
Step 6. Users can print image, e-mail it, include it in a document,
or place it on a Web page.
Step 4. Light is converted to analog electrical current that is
converted to digital signal by an analog-to-digital converter
(ADC).
Step 5. Digital information is sent to memory in the computer
to be used by illustration, desktop publishing, or other software;
or it is stored on disk.

What is an optical reader?
 Optical character recognition
(OCR) reads characters in
OCR font
 Optical mark recognition (OMR)
reads hand-drawn pencil marks,
such as small circles
 Device that uses light source to read characters, marks, and
codes and then converts them into digital data

What is Output?
What is output?
• Data that has been processed into a useful, consumable form
 Output device is any hardware component that can convey
information to user

Output Devices
Output Devices
Display data after they have been processed.
Cathode Ray Tube (CRT)
The most popular form of information output.
It works much like a television picture tube, with an electronic
gun shooting a beam of electrons to illuminate the pixels on the
screen. These are the “non-flat panel” monitors.
Printers
Produce a printed hard copy of information output.
Include impact printers ( dot-matrix printer), and non-impact
printers (laser, inkjet, and thermal transfer printers).

Output Devices
Plotters
To created high-quality graphics documents with multicolored pens to
draw computer output.
Slower than printers but are useful for outputting large-size charts,
maps or drawing.
Voice output devices
Converts digital output data into intelligible speech.
Speakers
To deliver an audio output such as music, that is connected to the
computer.

Types of Ports
• A port serves as an interface
between the computer (input
device) and other computers or
peripheral devices (output device).
The chart on the right illustrates
the key ports used on computers
today that connect various output
device types we will discuss in the
next few slides.

Display Devices
What is a display device?
p. 302
 Output device that visually conveys information
 Information on display device sometimes
called soft copy
 Monitors house display device as separate peripheral

CRT Monitors
What is a CRT monitor?
• Contains cathode-ray tube (CRT)
• Screen coated with tiny dots of
phosphor material
• Each dot consists of a red,
blue, and green phosphor
• Common sizes are 15, 17, 19,
21, and 22 inches
• Viewable size is diagonal
measurement of actual
viewing area

CRT Monitors
How does video travel from the processor to a CRT monitor?
Step 1. The
processor sends
digital video data to
the video card.
Step 2. The video card’s digital-
to-analog converter (DAC)
converts the digital video data
to an analog signal.
Step 3. The analog
signal is sent
through a cable to
the CRT monitor. Step 4. The CRT
monitor separates
the analog signal
into red, green,
and blue signals.
Step 5. Electron guns fire
the three color signals to the
front of the CRT.
Step 6. An image is displayed
on the screen when the
electrons hit phosphor dots on
the back of the screen.
• Video cards (also called a graphics cards) converts digital output
from computer into analog video signal

LCD & LED Monitors
The term LCD stands for liquid crystal display. LCDs use
liquid crystals to express what you see on the screen. The
crystals act as a shutter for the backlight, and, depending on
the type of charge given to them by the monitor's built-in
electrodes, the crystals will either allow light through to the
user or shut it out, thereby allowing the pixels to express their
appropriate colors, making up what you see on the screen.
LED-based monitors are still LCDs (they still use liquid
crystals to express images onscreen), but they use a
different type of backlight than what is normally used. Most
monitors of the last few years have used cold cathode
fluorescent (CCFL) tubes as their backlight of choice.
These two type monitors have effectively replaced most CRT
monitors types.

Printers
What is a printer?
• Output device that produces text
and graphics on paper
• Result is hard copy, or printout
• Two orientations: portrait and
landscape
portrait
landscape

Speakers and Headsets
What is an audio output device?
• Computer component that produces music, speech, or other sounds
• Speakers and headsets are common devices

Speakers and Headsets
What is voice output?
• Computer talks to you through speakers on computer
• Internet telephony allows you to have conversation
over Web

Types of Computers
• Computers in schools can be used for solving many different
types of problems.
• Available in many sizes and a wide range of capabilities.
• Can be classified as follows:
1. Microcomputers
2. Minicomputers
3. Mainframe computers
4. Supercomputers

Microcomputers
• Sometimes referred to as a personal computer (PC), is one
that can be placed on a desktop or carried from room to
room.
• The smallest microcomputers are known as laptop computers
or notebook computers.
• Desktop computers are compact microcomputer systems that
fit on a desk and are designed for use by individuals.
• A workstation is the largest type of microcomputer and is
generally used in scientific and engineering applications.

Minicomputers
• More powerful and more expensive than microcomputers.
• Are smaller and cheaper compared to mainframes.
• Also can be server, which is used for managing internal
company networks or Web sites.
• Server computers are specifically optimized to support a
computer network enabling users to share files, software,
peripheral devices (such as printers), or other network
resources.

Mainframe Computer
• The largest computer, a powerhouse with massive memory and
e extremely rapid processing power.
• It is used for very large business, scientific or military
application where a computer must handle massive amounts of
data or many complicated processes.

Supercomputer
• Is highly sophisticated and powerful computer that is used for
tasks requiring extremely rapid and complex calculations with
hundreds of thousands of variable factors.
• Used in many areas of scientific research, weather prediction,
aircraft design, nuclear weapon and so on.

Computer Software
Application Software
• Refers to programs that are developed to solve some specific
problems.
• There are two types of application software:
• application program to solve special classes of
problems
• Application programs that you can write to solve your
own problems.
• Examples of application software:
• word processing
• database programs
• spreadsheets
• graphic programs

Types of System Software
System Software
Refers to programs that make the computer usable and
accessible to the developers and programmers of
applications software.
Examples of system software:
• Operating systems
• Language translator
• Linker
• Loader
• Preprocessors

What is an Operating System?
• Operating System:
• Part of the computing system that manages all of the
hardware and software
• Controls every file, every device, every section of main
memory, and every nanosecond of processing time
• Controls who can use the system and how
• Computer system consists of:
• Software (programs)
• Hardware (the physical machine and its electronic
components)

Operating System Software
Essential managers of an operating system:
• Memory Manager
• Processor Manager
• Device Manager
• File Manager
Each manager both works closely with the other managers and
performs its unique role
User Command Interface is unique to each operating system

(continued)
Each subsystem manager must perform the following tasks:
• Monitor its resources continuously
• Enforce the policies that determine who gets what, when,
and how much
• Allocate the resource when it;s appropriate
• Deallocates the resource when appropriate

71
Operating System Software Functions

(continued)
Memory Manager: In charge of main memory (RAM)
Responsibilities include:
• Preserves the space in main memory occupied by the
operating system
• Checks the validity of each request for memory space
• Sets up a table to keep track of who is using which section
of memory in a multiuser environment
• Deallocates memory when the time comes to reclaim the
memory

(continued)
Processor Manager decides how to allocate the central
processing unit (CPU)
Processor Manager has two levels of responsibility:
• To handle jobs as they enter the system
• Handled by Job Scheduler
• To manage each process within those jobs
• Handled by Process Scheduler

(continued)
Device Manager monitors every device, channel, and control unit
• Chooses the most efficient way to allocate all of the
system’s devices, printers, terminals, disk drives, based on a
scheduling policy
• Makes the allocation, starts its operation
• Deallocates the device

(continued)
File Manager keeps track of every file in the system including data
files, assemblers, compilers, and application programs
• Enforces restrictions on who has access to which files by
using predetermined access
• Controls what users are allowed to do with files once they
access them
• Allocates the resource by opening the file and deallocates it
by closing the file

(continued)
Operating systems with networking capability have a fifth essential
manager called the Network Manager
Network Manager provides a convenient way for users to share
resources while controlling users’ access to them. The resources
include:
• Hardware (such as CPUs, memory areas, printers, tape
drives, modems, and disk drives)
• Software (such as compilers, application programs, and
data files)

Types of Operating Systems
(continued)
Operating systems for computers fall into following five
categories:
Batch
Interactive
Real-time
Hybrid
Embedded
Distinguished by response time and how data is
entered into the system

(continued)
Batch Systems:
• Relied on punched cards or tape for input in past
• Efficiency of the system was measured in throughput
Interactive Systems:
• Gives a faster turnaround than batch systems but are slower
than the real-time systems
• Introduced for users who needed fast turnaround when
debugging their programs
• Operating system required the development of time sharing
software

(continued)
Real-time systems:
Fastest and used in time-critical environments
Real-time systems are used for:
• Space flights, airport traffic control, high-speed aircraft
• Industrial processes
• Sophisticated medical equipment
• Distribution of electricity
• Telephone switching
A real-time system must be 100 percent responsive, 100
percent of the time

(continued)
Hybrid Systems:
• Combination of batch and interactive
• Accepts and runs batch programs in the background when the
interactive load is light
Embedded Systems:
• Computers placed inside other products to add features and
capabilities
• Operating systems with small kernel and flexible functions
capabilities will have potential for embedded system

Current Operating Systems
Primary design features of current operating systems are based on
providing support for
• Multimedia applications
• Internet and Web access
• Client/server computing
Computer systems are required to have
• Increased CPU speed
• High-speed network attachments
• Increased number and variety of storage devices

Lecture 2 - Computer Hardware & Operating Systems

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Lecture 2 - Computer Hardware & Operating Systems