Program General Structure

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Program General Structure

• Data descriptions, which define all the data to
  be manipulated and transformed by the
  instructions.
• A sequence of instructions, which defines all the
  transformations to be carried out on the data in
  order to produce the desired results.

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Structure of a Program
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Software

• The system software is a collection of programs
  that control the activities and functions of the
  various hardware components. An example of system
  software is the operating system, such as Unix,
  Windows, MacOS, OS/2, and others.
• Application software consists of those programs
  that solve specific problems for the users. These
  programs execute under control of the system
  software. Application programs are developed by
  individuals and organizations for solving
  specific problems.

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Programming Languages

• A programming language is a formal notation that
  is used to write the data description and the
  instructions of a program.
• A language has a well-defined set of syntax and
  semantic rules.
• The syntax rules describe how to write sentences.
  The semantic rules describe the meaning of the
  sentences. These two types of rules must be
  consistent.

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High-level Programming Languages

• The purpose of a programming language is to allow
  a human to write instructions to the computer in
  the form of a program.
• Are so called because they are hardware
  independent and closer to the problem (or family
  of problems) to be solved.
• Allow more readable programs, and that are easier
  to write and maintain. Examples of these
  languages are Pascal, C, Cobol, Fortran, Algol,
  Ada, Smalltalk, C, Eiffel, and Java.

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Compilation

• The solution to a problem is implemented in an
  appropriate programming language. This becomes
  the source program written in a high-level
  programming language, such as C, Eiffel, Java,
  or others.
• Once a source program is written, it is compiled
  or translated to an equivalent program in machine
  language.
• The computer can only execute instructions that
  are in machine language.

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Compiling a Java Program
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Compiling Java Programs

• The Java compiler checks for syntax errors in the
  source program and then translates it into a
  program in byte-code, which is the program in an
  intermediate form.
• The Java bytecode is not dependent of any
  particular platform or computer system. This
  makes the bytecode very portable from one machine
  to another.

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Executing a Program in Bytecode
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KJP Translator

• The KJP translator analyzes the syntax of the
  program and then to converts the program from KJP
  to Java.

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KJP Notation

• With the KJP translator, students can quickly
  convert their OO programs to Java.
• KJP can be integrated with jGRASP.
• The semantics of KJP is the same as that of Java.
  

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Problem Solving

• Computer problem solving involves a series of
  tasks or phases to develop a computer solution.
• To carry out this process of developing programs
  in an appropriate manner, basic knowledge of the
  software development process is essential.

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Goal of Problem Solving

• Solve some real-world problem producing good
  quality software at a reasonable cost.
• The real challenge is to find some method of
  solution or some way to approximate a solution to
  the problem at hand.

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Problem Solving Process

• Computer problem solving is a creative process
  in a simple manner, it involves
• Describing the problem in a clear and unambiguous
  form
• Finding a solution to the problem
• Developing a computer implementation of the
  solution

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Parts of a Problem

• The given data
• Required results
• The necessary transformation to be carried out on
  the given data to produce the final results

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Algorithm

• The transformation on the data is described as a
  sequence of instructions that are to be carried
  out on the given data in order to produce the
  desired results.
• Transformation is a clear, detailed, precise, and
  complete description of the sequence of
  operations.
• The algorithm is a precise description of how to
  solve the problem.

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Transformation Applied to the Input Data
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A Program

• A group of data descriptions and one or more
  sequences of instructions to the computer for
  producing correct results when given appropriate
  data.
• Written in an appropriate programming language
  and it tells the computer how to transform the
  given data into correct results.

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Software Development Process

• A process for producing the software that
  implements the solution on a computer.
• Guides the developer into a well-defined process
  to be carried out in a disciplined manner and to
  accomplish development of correct software.
• The life cycle is used to organize and manage the
  software development process including the phases
  to maintain and retire the software.

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Software Life Cycle

• The entire development process consists of a
  sequence of activities or phases that are carried
  out by a team of developers.
• These activities represent the complete life of
  the software from birth to retirement.

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Understanding Life cycle

• Software development, which includes all the
  phases necessary to carry out the initial
  development of the software product.
• Using the developed software, this includes the
  activities that support the software in
  production.
• Maintenance, which include the activities that
  report defects in the software and the subsequent
  fixes and releases of new versions of the
  software product.
• Retirement, which takes the software off
  production when it can no longer be maintained.

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Waterfall Model

• One of the earliest and simplest models for the
  software life cycle is the waterfall model.
• This model represents the sequence of activities
  to develop the software system up to installation
  for using the software.
• The activity in a given stage or phase cannot be
  started until the activity of the previous phase
  has been completed.

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The Waterfall Model of Development Process
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Tasks in the Software Development Process

• Analysis
• Design
• Implementation
• Testing
• Deployment

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Analysis

• Describes what the problem solution is supposed
  to accomplish. The outcomes of this phase are the
  various requirement documents, which include
  specifying the requirements of the problem in a
  more complete, precise, clear, and understandable
  form.
• Entails a thorough understanding of the problem
  and describing the problem in a very precise
  manner and what is to be done.

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Design

• Describes the structure and behavior of the
  components of the system model. The outcome of
  this phase is a detailed description of the data
  structures and algorithms in each component of
  the model.
• The decomposition of the software into smaller
  parts is usually part of the preliminary design.
  The rationale for this step is that it is much
  easier to manage small pieces of the software
  instead of the whole product.

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Design (Cont.)

• The detailed design may be the most
  intellectually challenging in program
  development.
• In this phase, one or more solutions to the
  problem are investigated. The data structures and
  the algorithms are designed, written in some
  appropriate notation (i.e., pseudo-code and/or
  flowcharts), and documented.

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Implementation

• Includes the translation of the design solution
  into a programming language, followed by the
  compilation of the code written.
• This is the actual construction of the program(s)
  for the application. The outcome of this phase is
  the set of programs constructed.

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Testing

• Verifies the program(s) that the program works
  according to requirements with appropriate data
  according to the set of examples provided.
• This phase includes unit testing, which involves
  the testing of individual components (modules),
  and integration testing, which involves testing
  all the components together.
• The outcome of this phase is the verified
  application software.

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Limitation of the Waterfall Model

• It is not iterative, which is extremely necessary
  in practice.
• There are some variations proposed for the
  waterfall model. These include returning to the
  previous phase when necessary.
• Recent trends in system development have
  emphasized the iterative approach. In this
  approach, previous stages can be revised and
  enhanced.

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Other Life cycle Models

• The spiral model of software development is a
  more complete model that incorporates the
  construction of prototypes in the early stages.
• A prototype is an early version of the
  application that does not have all the final
  characteristics.
• Other development approaches involve prototyping
  and rapid application development (RAD).