Today and Tomorrow 12 th Edition Understanding Computers Chapter 13: Program Development and Programming Languages
Dec 25, 2015
Today and Tomorrow 12th Edition
Understanding Computers
Chapter 13:
Program Development and Programming
Languages
Chapter 13 Understanding Computers, 12th Edition 2
Learning Objectives
• Understand the differences between structured programming, object-oriented programming (OOP), aspect-oriented programming (AOP), and adaptive software development.
• Identify and describe the activities involved in the program development life cycle (PDLC).
• Understand what constitutes good program design and list several tools that can be used by computer professionals when designing a program.
Chapter 13 Understanding Computers, 12th Edition 3
Learning Objectives• Explain the three basic control structures and how
they can be used to control program flow during execution.
• Discuss some of the activities involved with coding, debugging, maintaining, documenting, and ensuring the quality of programs.
• List some tools that can be used to speed up or otherwise facilitate the program development process.
• Describe several programming languages in use today.
Chapter 13 Understanding Computers, 12th Edition 4
Overview• This chapter covers:
– The most common approaches to program design and development
– The steps in the program development life cycle (PDLC)
– Tools that can facilitate program development
– Popular programming languages
Chapter 13 Understanding Computers, 12th Edition 5
Approaches to Program Design and Development
• Procedural programming: Focuses on the step-by-step instructions that tell the computer what to do– Uses procedures (modules, subprograms): Smaller
sections of code that perform particular tasks– Allows each procedure to be performed as many
times as needed without requiring multiple copies of code
– Prior to procedural programming, programs were one large set of instructions containing statements that sent control to different parts of the program as needed (i.e. GOTO statements)
– Structured programming: Breaks the program into small chunks
• Top-down design
Chapter 13 Understanding Computers, 12th Edition 6
Approaches to Program Design and Development
– Variables: Named memory locations that are defined for a program
• Used to store the current value of data items used in the program
Chapter 13 Understanding Computers, 12th Edition 7
Approaches to Program Design and Development
• Object-oriented programming (OOP): Programs consist of a collection of objects
– Objects: Contain data and methods to be used with that data
– Class: Group of objects that share some common properties
– Instance: An individual object in a class
– Attributes: Data about the state of an object
– Methods: Perform actions on an object
Chapter 13 Understanding Computers, 12th Edition 8
Approaches to Program Design and Development
• Aspect-oriented programming (AOP): Breaks program into small pieces that overlap in functionality as little as possible
– Program components can be developed and modified individually, and easily reused
• Adaptive software development: Designed to make program development faster and more efficient and focus on adapting the program as it is being written– Iterative: Cyclical approach that allows the
repetition of steps and tasks as needed– Incremental: Developing one piece at a time– Includes RAD (rapid application development) and
extreme programming (XP)– More recent adaptive software development
approaches are called agile software development
Chapter 13 Understanding Computers, 12th Edition 9
The Program Development Life Cycle (PDLC)
• Program development: The process of creating application programs
• Program development life cycle (PDLC):The steps involved with creating programs:
Chapter 13 Understanding Computers, 12th Edition 10
• Problem analysis: The problem is considered and the program specifications are developed
– Specifications developed during the SDLC are reviewed by the systems analyst and the programmer (the person who will code the program)
– Goal: To understand the functions the software must perform
– Documentation: Includes program specifications (what it does, timetable, programming language to be used, etc)
The Program Development Life Cycle (PDLC)
Chapter 13 Understanding Computers, 12th Edition 11
• Program design: The set of steps needed in order for the program to perform the tasks it is supposed to perform (algorithm) is developed
– Good program design is extremely important
– Program design tools
• Structure charts: Depict the overall organization of a program
• Flowcharts: Show graphically step-by-step how a computer program will process data
• Use special symbols andrelational operators
The Program Development Life Cycle (PDLC)
Chapter 13 Understanding Computers, 12th Edition 12
Flowcharts
Chapter 13 Understanding Computers, 12th Edition 13
• Pseudocode: Uses English-like statements to outline the logic of a program
The Program Development Life Cycle (PDLC)
Chapter 13 Understanding Computers, 12th Edition 14
• Unified Modeling Language (UML) Models: Set of standard notations for creating business models
– Widely used in object-oriented programs– Includes class diagrams, use case diagrams,
etc.• Business Processing Modeling Notation
(BPMN): Graphical notation used to depict the steps in a business process
– Expresses business processes graphically using Business Process Diagrams
– Look similar to flowcharts– Designed to be understood by everyone
The Program Development Life Cycle (PDLC)
Chapter 13 Understanding Computers, 12th Edition 15
Unified Modeling Language (UML) Models
Chapter 13 Understanding Computers, 12th Edition 16
The Program Development Life Cycle (PDLC)
– Control structure: A Pattern for controlling the flow of logic in a computer program
• Sequence control structure: Series of statements that follow one another
• Selection control structure: Multiple paths, direction depends on result of test
– If-then-else
– Case
• Repetition control structure: Repeat series of steps
– Do-while
– Do-until
Chapter 13 Understanding Computers, 12th Edition 17
Control Structures
Chapter 13 Understanding Computers, 12th Edition 18
Control Structures
Chapter 13 Understanding Computers, 12th Edition 19
The Program Development Life Cycle (PDLC)
– Good program design: • Saves time• Creates better programs
– Good program design principles:• Be specific
– All things the program must do need to be specified
• One-entry-point/one-exit-point rule• No infinite loops or other logic errors
– Infinite loop: Series of steps that repeat forever
– Design should be tested to ensure logic is correct• Desk check; tracing tables
– Documentation: Includes design specifications
Chapter 13 Understanding Computers, 12th Edition 20
Good Program Design
Chapter 13 Understanding Computers, 12th Edition 21
Program Design Testing
Chapter 13 Understanding Computers, 12th Edition 22
The Program Development Life Cycle (PDLC)
• Program coding: The process of writing the programming language statements to create a computer program– When choosing a programming language,
consider:• Suitability to the application• Integration with other programs• Standards for the company • Programmer availability• Portability if being run on multiple platforms• Development speed
– Coding creates source code
Chapter 13 Understanding Computers, 12th Edition 23
Coding Standards– Coding standards: A list of rules designed to
standardize programming styles• Make programs more universally readable and
easier to maintain• Includes the proper use of comments to:
– Identify the programmer and last modification date
– Explain variables used in the program– Identify the main parts of the program
– Reusable code: Generic code segments that can be used over and over again with minor modifications
• Can greatly reduce development time– Documentation: Includes documented source code
Chapter 13 Understanding Computers, 12th Edition 24
Coding Standards
Chapter 13 Understanding Computers, 12th Edition 25
The Program Development Life Cycle (PDLC)
• Program debugging and testing: The process of ensuring a program is free of errors (bugs) and works as it is supposed to
– Before they can be debugged, coded programs need to be translated into executable code
• Source code: Coded program before it is compiled
• Object code: Machine language version of a program
• Language translator: Program that converts source code to machine language
Chapter 13 Understanding Computers, 12th Edition 26
The Program Development Life Cycle (PDLC)
• Types of language translators:
– Compilers: Combines program with other object modules and creates a finished executable program
– Interpreters: Translates one line of code at one time
– Assemblers: Convert assembly language programs into machine language
Chapter 13 Understanding Computers, 12th Edition 27
The Program Development Life Cycle (PDLC)
E Preliminary debugging: Finds initial errors• Compiler errors: Must be corrected before the
logic of the program can be tested• Syntax errors: Occur when the programmer
has not followed the rules of the programming language
E Program won’t run; usually an error message is displayed
• Run time error: Occurs when the program is running
E Often logic errors: Program will run but produces incorrect results
E Dummy print statements can help locate logic errors and other run time errors
Chapter 13 Understanding Computers, 12th Edition 28
Preliminary Debugging
Chapter 13 Understanding Computers, 12th Edition 29
Preliminary Debugging
Chapter 13 Understanding Computers, 12th Edition 30
The Program Development Life Cycle (PDLC)
– Testing occurs after the program appears to be correct to find any additional errors
• Should use good test data • Tests conditions that will occur when the
program is implemented• Should check for coding omissions (product
quantity allowed to be < 0, etc.)• Alpha test (inside organization)• Beta test (outside testers)
– Documentation: Completed program package (user’s manual, description of software commands, troubleshooting guide to help with difficulties, etc.)
Chapter 13 Understanding Computers, 12th Edition 31
The Program Development Life Cycle (PDLC)
• Program implementation and maintenance: Installing and maintaining the program
– Once the system containing the program is up and running, the implementation process is complete
– Program maintenance: Process of updating software so it continues to be useful
• Very costly
– Documentation: Amended program package
Chapter 13 Understanding Computers, 12th Edition 32
Tools for FacilitatingProgram Development
• Application Lifecycle Management (ALM): Creating and managing an application during its entire lifecycle, from design through testing
– Tools include:
• Requirements management: Keeping track of and managing the information needs of users
– Requirements definition software
– Requirements management software
• Configuration management: Keeping track of the progress of a program development project
• Program design tools to generate diagrams, code, etc.
Chapter 13 Understanding Computers, 12th Edition 33
Tools for FacilitatingProgram Development
• Application generator: Software product that enables users to code new applications quickly– Macro recorders: Record and play back a series of
keystrokes
– Report and form generators: GUI tools that enable individuals to prepare reports and forms quickly
Chapter 13 Understanding Computers, 12th Edition 34
Tools for FacilitatingProgram Development
• Device software development tools: Assist with developing software to be used on devices, such as cars, ATM machines, consumer devices, etc
• Software development kits (SDK): Programming package designed for a particular platform that enables programmers to develop applications more quickly and easily– Released by hardware or software companies
(Microsoft, Apple, etc.)• Application Program Interfaces (API): An interface
designed to help applications interface with a particular operating system– Often used in conjunction with Web sites
Chapter 13 Understanding Computers, 12th Edition 35
Programming Languages• Programming language: A set of rules used to write
computer programs– To write a program, you need appropriate software
for the programming language you will be using• Categories of programming languages
– Low-level languages: Difficult to code in; machine dependent
• Machine language: 1s and 0s• Assembly language: Includes some words and
symbols
Chapter 13 Understanding Computers, 12th Edition 36
Programming Languages
Chapter 13 Understanding Computers, 12th Edition 37
Programming Languages– High-level languages: Closer to natural languages
and so are easier to write in• Machine independent• Includes third-level procedural languages such
as FORTRAN, BASIC, COBOL, Pascal, and C, as well as newer object-oriented languages such as Visual Basic, C++, C#, Python, Ruby, and Java
– Fourth-generation languages (4GLs): Even closer to natural languages and easier to work with than 3GLs
• Declarative rather than procedural• Includes structured query language (SQL) used
with databases
Chapter 13 Understanding Computers, 12th Edition 38
Programming Languages
– Natural programming languages: Users can communicate in their native language
• Doesn’t have to follow program syntax• In the infancy stage
– Visual programming languages: Uses a visual programming environment
• User can use mouse and graphical interface and the code is automatically generated
• Visual versions of many programming languages
• Visual programming environment (VPE): Use visual elements to assist in program development but still require some coding
Chapter 13 Understanding Computers, 12th Edition 39
Common Programming Languages
• FORTRAN: High-level programming language used for mathematical, scientific, and engineering applications
– Efficient for math and scientific applications
Chapter 13 Understanding Computers, 12th Edition 40
Common Programming Languages• COBOL: Designed for business transaction
processing– Makes extensive use of modules and submodules– Being phased out in many organizations
Chapter 13 Understanding Computers, 12th Edition 41
Common Programming Languages• Pascal: Created as a teaching tool to encourage
structured programming– Contains a variety of control structures used to
manipulate modules systematically
Chapter 13 Understanding Computers, 12th Edition 42
Common Programming Languages• BASIC: Easy-to-learn, high-level programming
language that was developed to be used by beginning programmers
– Visual Basic: Object-oriented version of BASIC which helps programmers quickly and easily create programs through the use of a visual environment
Chapter 13 Understanding Computers, 12th Edition 43
Common Programming Languages• C: Designed for system programming
• C++, and C#: Object-oriented versions of C
Chapter 13 Understanding Computers, 12th Edition 44
Common Programming Languages
• Java: High-level, object-oriented programming language frequently used for Web-based applications– Platform independence is one of Java’s biggest
advantages– Any operating system or browser that understands
Java (compiled Java programs) can run Java bytecode applications
– Is one of the most popular programming languages today
– Can be used to write Java applets
Chapter 13 Understanding Computers, 12th Edition 45
Common Programming Languages
Chapter 13 Understanding Computers, 12th Edition 46
Common Programming Languages• Python: Open-source, dynamic, object-oriented
language that can be used to develop a variety of applications– Gaming, scientific, database, and Web applications– Only recently gaining a following
Chapter 13 Understanding Computers, 12th Edition 47
Common Programming Languages• Ruby: Open-source, object-oriented language that can
be used to create general-purpose or Web applications
– Uses a syntax that is fairly easy to read and write, allowing programmers to create database-driven Web applications easily and quickly
Chapter 13 Understanding Computers, 12th Edition 48
Summary• Approaches to Program Design and Development
• The Program Development Life Cycle (PDLC)
• Tools for Facilitating Program Development
• Programming Languages