Ppt chapter01

Chapter 1
Background
Fundamentals of Java

2
Objectives
 Give a brief history of computers.
 Describe how hardware and software make
up computer architecture.
 Understand the binary representation of data
and programs in computers.

3
Objectives (cont.)
 Discuss the evolution of programming
languages.
 Describe the software development process.
 Discuss the fundamental concepts of object-
oriented programming.

4
Vocabulary
 Application software
 Bit
 Byte
 Central processing unit (CPU)
 Hardware
 Information hiding
 Object-oriented programming

5
Vocabulary (cont.)
 Primary memory
 Secondary memory
 Software
 Software development life cycle (SDLC)
 System software
 Ubiquitous computing
 Waterfall model

6
History of Computers
 1940s: ENIAC (One of world’s first digital
electronic computers)
 1950s: IBM sells first business computers
 1960s: Time-sharing computers
 1970s: Networking takes hold

7
History of Computers (cont.)
 1980s: Many PCs, LANs become popular
 1990s: Explosion in computer use
– Internet becomes prevalent
 21st century: Ubiquitous computing

8
Computer Hardware and Software
 Hardware: Physical devices that you see on
your desktop
 Software: Programs that give the hardware
useful functionality

9
Bits and Bytes
 Bit (binary digit): Smallest unit of
information processed by a computer
– A single 0 or 1
 Byte: 8 adjacent bits
 Capacity of computer memory and storage
devices usually expressed in bytes

10
Bits and Bytes (cont.)
Table 1-1: Some commonly used quantities of information
storage

11
Computer Hardware
 Six major sub-systems:
– User interface: Supports moment-to-moment
communication between user and computer
 Keyboard and mouse
– Auxiliary I/O devices: Printers and scanners
– Auxiliary storage devices: Secondary
memory
 Hard disks, CD-ROMS, flash memory sticks

12
Computer Hardware (cont.)
 Six major sub-systems (continued):
– Network connection: Connection to Internet
 Modems
– Internal memory: Random access memory
(RAM) or primary memory
 Fast and relatively small
– Central processing unit (CPU): Performs the
work on a computer
 Consists of billions of transistors

13
Computer Software: System
Software
 Supports basic operations of a computer and
allows human interaction
– Operating system
– Communications software
– Compilers
– User interface subsystem

14
Computer Software: Application
Software
 Allows human users to accomplish
specialized tasks
– Word processors
– Spreadsheets
– Database systems
– Multimedia software

15
Binary Representation of
Information & Computer Memory
 Computer memory stores patterns of
electronic signals.
– CPU reads, manipulates, and transforms
patterns.
– Patterns can be stored/viewed as strings of bits.
 Sequences of 1s and 0s
– To determine what a sequence of bits
represents, you must know the context.

16
Integers
 Computers use binary (base 2) notation.
– 100112 = (1 * 24) + (0 * 23) + (0 * 22) + (1 * 21) +
(1 * 20)
 Computer scientists use binary, octal (base
8), and hexadecimal (base 16) notation.

17
Integers (cont.)
Table 1-2: Some base 10 numbers and their base 2 equivalents

18
Floating-Point Numbers
 Numbers with a fractional part
 Mantissa/exponent notation: Number is
rewritten as a value between 0 and 1 times a
power of 10.
– 354.9810 = 0.3549810 * 103
 IEEE standard: Mantissa contains one digit
before the decimal point.

19
Characters and Strings
 ASCII (American Standard Code for
Information Interchange) encoding
scheme: Each character represented as a
pattern of 8 bits (1 byte)
– 256 characters may be represented
 Java uses Unicode encoding scheme:
– 2 bytes used to represent a character
– 65,536 characters may be represented

20
Characters and Strings (cont.)
Table 1-3: Some characters and their corresponding
ASCII bit patterns

21
Sound
 Information contained in sound is analog.
– Continuous waveform
 In order to represent in a computer, sound
must be digitized.
– Sampled at regular intervals on the waveform
– Standard sampling rate is 44,000 samples per
second
 Requires large amount of storage

22
Sound (cont.)
Figure 1-4a: Sampling a waveform

23
Images
 Also analog information
– Set of color and intensity values spread across
a two-dimensional space
– Sampling devices: Scanners and digital
cameras
– Measure discrete values at pixels on a grid
 Black-and-white: 2 bits per pixel
 Grayscale: 8 bits per pixel for 256 shades of gray
 True color (RGB): 24 bits per pixel

24
Video
 Consists of a soundtrack and frames
– Sets of images recorded in sequence during a
given time interval
 Primary challenge in digitizing video is data
compression

25
Program Instructions
 Represented as a sequence of bits in RAM
 Example:
– 0000 1001 / 0100 0000 / 0100 0010 / 0100 0100
 First 8 bits represent the ADD command
– Operation code or opcode
 Second 8 bits represent first operand
 Third 8 bits represent second operand
 Fourth 8 bits used to store sum

26
Computer Memory
 Address: A byte’s location in memory
– Numbered from 0 to 1 less than the number of
bytes of memory installed on the computer
– Adjacent bytes may store different types of
data.
 Depends on context

27
Computer Memory (cont.)
Figure 1-5: A 32MB RAM

28
Programming Languages
 Generation 1—machine languages:
Program data entered directly into RAM in
form of 1s and 0s
– Using switches and, later, punch cards
– Error prone, tedious, and slow

29
Programming Languages (cont.)
 Generation 2—assembly languages:
Mnemonic symbols represent instructions
and data.
– One-to-one correspondence with machine-
language instructions
 Assembler: Translates to machine language
 Loader: Loads machine language into memory

30
Programming Languages (cont.)
 Generation 3—high-level languages:
Designed to be easy to write, read, and
manipulate.
– C, C++, Java
– High-level instructions may represent many
machine-language instructions.
– Compiler translates high-level language into
machine language.

31
The Software Development
Process
 Software development life cycle (SDLC): A
view of software development in which
phases of development occur incrementally
 Standardizes software development
– Simplifies understanding the project scope
– Minimizes software flaws

32
Process (cont.)
 Waterfall model: A version of the SDLC
– Phases:
 Customer request
 Analysis
 Design
 Implementation
 Integration
 Maintenance

33
Process (cont.)
Figure 1-6: Waterfall
model of the software
development life cycle

34
Process (cont.)
Figure 1-7: Relative costs of repairing mistakes when
found in different phases

35
Process (cont.)
Figure 1-8: Percentage of total cost incurred in each
phase of the development process

36
Basic Concepts of Object-
Oriented Programming
 Two major groups of high-level languages:
– Procedural languages: COBOL, FORTRAN,
BASIC, C, Pascal
– Object-oriented languages: Smalltalk, C++,
Java
 Object-oriented approach is superior

37
Oriented Programming (cont.)
 Object-oriented programming takes a divide-
and-conquer approach to reduce code.
– Code can easily be reused
 A program consists of different types of
software components called classes.
– Defines data resources and methods
 Rules of behavior

38
 Encapsulation: Combining the description
of resources and behaviors into a single
software entity
 A program is written first and then run.
 A running program is composed of
interacting objects.
– Each object’s data resources (instance
variables) and rules of behavior (methods) are
defined by a class.

39
Oriented Programming (Cont.)
 While a program is executing, it instantiates
(creates) objects as needed.
 Objects work together to accomplish the
mission of the program.
– Send each other messages to request services
or data
 When an object receives a message, it refers
to its class to find the corresponding method
to execute.

40
 Information hiding: Providing access to
services, but not to data resources
 Classes are organized in a hierarchy.
 Root class defines methods and instance
variables shared by its subclasses.
– Those below it in the hierarchy
 Subclasses define additional methods and
instance variables.

41
 Inheritance: The hierarchical class structure
and sharing of instance variables and
methods with subclasses
 Polymorphism: Different types of objects
can understand the same message.
– An object’s response to a message depends on
the object’s class.

42
Summary
 The modern computer age began in the late
1940s with the development of ENIAC.
Business computing became practical in the
1950s, and time-sharing computers
advanced computing in large organizations in
the 1960s and 1970s. The 1980s saw the
development and first widespread sales of
personal computers, and the 1990s saw
personal computers connected in networks.

43
Summary (cont.)
 Modern computers consist of two primary
components: hardware and software.
Computer hardware is the physical
component of the system. Computer
software consists of programs that enable us
to use the hardware.

44
Summary (cont.)
 All information used by a computer is
represented in binary form. This information
includes numbers, text, images, sound, and
program instructions.
 Programming languages have been
developed in the course of three generations:
generation 1 is machine language,
generation 2 is assembly language, and
generation 3 is high-level language.

45
Summary (cont.)
 The software development process consists
of several standard phases: customer
request, analysis, design, implementation,
integration, and maintenance.
 Object-oriented programming is a style of
programming that can lead to better quality
software. Breaking code into easily handled
components simplifies the job of writing a
large program.

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