Transcript SSD2: Introduction to Computer Systems

SSD2: Introduction to
Computer Systems
ISS,WHU
Unit 1. Computer Systems
1.1 Overview of Computer Systems
1.2 Evolution of Computer Systems
1.3 Data Representation in a Computer
System
Subsystems of a
Computer
Internet
Network System
•Internet services (email)
•Network connections (modems, network cards)
Hardware System
•Keyboard
•Monitor
•System unit
Software System
•Operating System (Unix, Mac OS, Microsoft
Windows)
•Web browser (Netscape, Internet Explorer)
•Office productivity applications (Microsoft
Office, Star Office)
Hardware System
Speakers
Monitor
Printer
System unit
Keyboard
Mouse
Hardware Components: Peripheral
Devices
Equipment added to computer to enhance its
functionality
Modify and expand the basic computer system
Examples of peripheral devices:
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Keyboard
Monitor
Mouse
Printer
Scanner
Digital Video Camera
Graphic Tablet
Joy Stick
Hardware Components: Storage
Devices
Optical Disks
– CD-ROM
– CD-RW
– DVD-ROM
Magnetic Disks
– Floppy disk
– Hard disk (removable & fixed)
What is Software?
Software is a set of computer instructions
or data.
Software receives input from the user and
processes this input through the computer
to produce output.
Software directs how the computer
interacts with the user.
Software specifies how to process the
user's data
Software System
Two categories:
– Operating system software,
– Application software
Users
Application Software
Operating System Software
Hardware System
Software System
Operating system software, also called system
software, is the master controller for all activities
that take place within a computer
– Examples of OS software:
Microsoft Windows
Unix
Mac OS
Application software is a set of one or more
computer programs that helps a personcarry out a
task
– Examples of application software:
Microsoft Word
Internet Explorer
Macromedia Dreamweaver
Adobe Acrobat Reader
Network System
A network provides connections among computers to enable
computers on a network to share data (e.g. documents), hardware
(e.g. printers), and software resources (e.g. application programs).
Network users can also send messages to each other.
A network must be secured to protect data from unauthorized usage
(e.g. using login name and password to gain access to a network).
Network connection
components:
•Network Interface Card
(NIC)
•Modem
•Phone line or cable
•Internet Service
Provider (ISP)
Internet
Basic Computer Model
All computers perform four basic
operations
– Input Data
– Process Data
– Store Data
– Output Data
Basic Operations
Input data is to feed information which can be supplied
by any person, environment or other computer.
Processing data is manipulating data by performing
calculations, sorting lists of words or numbers, drawing
pictures.
Storing data is for future retrieval and processing.
Memory holds data that is waiting to be processed, and
storage areas hold data permanently until the data is
deleted.
Output data is the result produced by a computer, which
includes reports, documents, music, graphs and pictures.
Categories of Computers
Computers are classified based on their
technology, function, physical size,
performance and cost. The categories of
computers include:
– Personal computers
– Handheld computers
– Mainframes
– Supercomputers
Personal Computer (PC)
Designed to meet the computing needs of
an individual
– Desktop computers
– Notebook computers
Handheld Computer
Designed to fit into a pocket,
run on batteries, and be used
while you are holding it
Also called a PDA (Personal
Digital Assistant)
– Send and receive e-mail
– Use maps and global positioning
– Maintain expense account,
contacts, to-do lists, memos, etc.
– Make voice calls using cellular
service
A personal digital
assistant (PDA)
accepts info
on a touch-sensitive
screen
Mainframe Computer
It is a large and expensive computer that is
capable of handling requests and passing
data simultaneously to many users.
Used by governments and large corporations
to provide centralized storage and control
Processes billions of data per second and
includes many units where one directs
overall operations, a second one handles
communication between users, and third
searches for requests given by user.
Supercomputer
It is the fastest type of computer.
Supercomputers are very expensive and are employed
for specialized applications that require immense
amounts of mathematical calculations.
It is often used for:
– Breaking codes
– Modeling weather systems
– Simulating nuclear explosions
– Research simulations
Capable of performing over 600 billion floating-point
operations per second.
Examples: Deep Blue, PARAM 1000, Hitachi's SR2201
Evolution of Computers
Needed calculation devices to keep track of
accounting for commerce
1200s—Manual Calculating Devices: the
abacus
Evolution of Computers (continued)
1600s—Mechanical Calculators
– Used wheels, gears, and counters
– To work a mechanical calculator, the operator
enters the numbers for a calculation, and then
pulls a lever or turns a wheel to carry out the
calculation
– Example: the Pascaline invented by Blaise
Pascal. It used some principles of the abacus,
but used wheels to move counters.
Evolution of Computers (continued)
1800s—Punched Cards（punched card ）
– Used holes following a specific pattern to represent the
instructions given to the machine or stored data
– Different program instructions can be stored on
separate punched cards, which can be fed through the
computing machine repeatedly.
– Once punched, the cards were fed into a card reader
that used an array of metal rods to electronically read
the data from the cards and tabulate the results. This is
called the Hollerith Tabulating Machine
– Hollerith incorporated The Tabulating Machine better
known today as IBM.
Evolution of Computers (continued)
Charles Babbage designed a new generalpurpose calculating device, the Analytical Engine,
which is the ancestor of modern computers.
– It included the essential components of present-day
computers, which are input, process, storage, and
output of data.
Evolution of Computers (continued)
1940s—Vacuum Tubes
– Used to control the flow of electrons. Since vacuum tubes
responded faster than mechanical components, faster
computations were possible. But, the tubes consumed a lot of
power and burned out quickly.
– The first computer prototype using vacuum tubes was ENIAC
(Electronic Numerical Integrator and Computer). It was designed
to calculate trajectory tables for the U.S. Army during World War II,
but it was not completed until three months after the war.
Evolution of Computers (continued)
1950s—Transistors
– Smaller, cheaper, more reliable, and consumed
less power than vacuum tubes.
– Could perform 200,000 to 250,000 calculations
per second.
Evolution of Computers (continued)
1960s—Integrated Circuits
– Thin slice of silicon packed with microscopic
circuit elements such as wire, transistors,
capacitors, and resistors.
– Enabled the equivalent of thousands of
vacuum tubes or transistors to be packed
onto a single miniature chip about the size of
your fingernail
– Reduces the physical size, weight, and power
requirements for devices such as computers
Evolution of Computers (continued)
1970s to Present—Microprocessor
– Combined components of a computer on a
microchip
– Can be manufactured and then programmed for
various purposes
Evolution of Computers (continued)
Pace of Processor Advancement
Applications of Computer
Systems
In Education
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Multimedia-Facilitated Learning
Simulation-Based Education
Intelligent Machine-Based Training
Interactive Learning
In Business
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Supply Chain Management
Project Management
Customer Relationship Management
Sales and Marketing Using Electronic Commerce
Manufacturing Research
Applications of Computer
Systems
In Entertainment
– Movies
– Video Games
– Music
– Digital Photography
– Travel
– Wearable Computer Systems
Developing new applications of computer systems:
– Research at Carnegie Mellon University
http://www.cs.cmu.edu/research/projects/
– Research at Massachusetts Institute of Technology
Media Lab http://www.media.mit.edu/
Computer Industry
Computer industry encompasses those companies that
manufacture handheld computers, personal computers, highend workstations, servers, mainframes, and supercomputers
Information technology industry (or IT industry), is typically
used to refer to the companies that develop, produce, sell, or
support computers, software, and computer-related products
IT companies include:
– Equipment manufacturers
– Chipmakers
– Software publishers
– Service companies
– Retailers
Computer Industry (continued)
The 1990s spawned a group of Internetbased companies that came to be called
“dot coms”, from the companies’ domain
names, which inevitably ended with “.com”
and many of the companies even
incorporated “.com” into their official
company names
Amazon.com was one of the first Internetbased companies
Computer Industry (continued)
Governments and private businesses have
discovered that they can become much
more efficient with a liberal application of
computers and other information
technologies
As businesses globalize, they encounter
new competitors with technological
advantages
Bottom line: if your business competitors
turn to technology, so must you
Careers in Computing
A systems analyst investigates the requirements of a
business or organization, its employees, and its
customers in order to plan and implement new or
improved computer services
A security specialist analyzes a computer system’s
vulnerability to threats from viruses, worms,
unauthorized access, and physical damage
A computer programmer designs, codes, and tests
computer programs
A quality assurance specialist participates in alpha
and beta test cycles of software
A database administrator analyzes a company’s data
to determine the most effective way to collect and store it
Careers in Computing
(continued)
A network specialist/administrator plans, installs, and
maintains one or more local area networks
A computer operator typically works with
minicomputers, mainframes, and supercomputers
A computer engineer designs and tests new hardware
products, such as computer chips, circuit boards,
computers, and peripheral devices
A technical support specialist provides phone or
online help to customers of computer companies and
software publishers
Careers in Computing
(continued)
A technical writer creates documentation for large
programming projects, and writes the online or printed
user manuals that accompany computers, peripheral
devices, and software
A computer salesperson, or “sales rep,” sells
computers
A Web site designer creates, tests, posts, and modifies
Web pages
A manufacturing technician participates in the
fabrication of computer chips, circuit boards, system
units, or peripheral devices
Careers in Computing
(continued)
The U.S. Bureau of Labor Statistics (BLS) projects that
the number of jobs in the computer industry will
substantially increase between now and 2008
According to the BLS, the largest increases in available
jobs will be for database administrators, computer
support specialists, and computer engineers
Over the next few years, economic trends may cause
significant changes in the job market
A daily look at in-demand tech skills can be viewed at:
http://mshiltonj.com/sm/
IT Salaries in the U.S.
Source: http://www.bls.gov
1.3 Data Representation in a
Computer System
1.3.1 Bits and Bytes
1.3.2 Number Systems
1.3.1 Bits and Bytes
Recall computers are made up of electrical components
Data can be represented electronically with electrical
components being on or off.
On and off states can be represented using digits 0s and
1s. For example:
– 0: Off state
– 1: On state
Thus, data can be represented digitally using digits 0
and 1.
0 and 1 are called binary digits.
Each binary digit is called a bit（二进制位，比特）.
Eight Bits equal to one byte （字节）.
Data Representation Using Binary
Digits
A piece of data, such as an alphabet letter, may
be represented using a sequence of binary
digits- 0's and 1's.
There are several types of codes used to
represent character data.
Extended ASCII (America Standard Code for
Information Interchange) code,
the alphabet letter "a" can be represented using
a series of eight binary digits, "01100001."
Extended ASCII code
uses eight bits (or one byte) to represent
input characters.
data representing
All data, including audio, visual, and
program instruction data can be
represented and stored using a sequence
of binary digits, or a sequence of bytes.
A file is a collection of data.
In some files, the bits of data directly
encode individual letters, numbers, and
punctuation symbols that make up words
and sentences.
In other files such as an image file, the bits
of data need to be computed in order for
them to transform to images that we can
interpret.
A file is a collection of data.
Most applications encode information in specialized
ways that are not readable by humans. such as
Microsoft Word or PowerPoint
even though Microsoft Word is often used to edit text, a
Word document cannot be properly displayed by a
simple text editor like Notepad because the document
includes information in a format specific to Microsoft
Word.
Therefore, it must be opened by Microsoft Word to be
read.
Some files have a header section that indicates which
format was used to encode the data in order to allow the
computer to reassemble the binary data back into the
human-readable form of the document.
Increasing Need for Bytes
Decade
1970s
Order of magnitude
in
Thousands
Storage capacity
Prefix
Abbreviation
Kilo
(103)
K
1980s
1990s
2000s
Millions
Billions
Trillions
Mega
(106)
Giga
(109)
Tera
(1012)
M
G
T
In terms of storage, more is
better—which
more information in the form of both data
and programs that act on that data can be
stored.
Corresponding to the growth in storage
capacity, memory capacity is also
increasing.
Moreover, memory technologies are
getting smaller, lighter, and faster, for
about the same price.
1.3.2 Number Systems
Decimal: base 10 (digits 0-9)
Binary: base 2 (digits 0-1)
Hexadecimal: base16 (digits 0-9 and A-F)
– Each hexadecimal digit represents four binary
places.
– Hex digit can be used as shorthand for binary
notation
One Hex digit
One byte = 8 bits
four bits
two Hex digits