Application Development

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Application Development

• SA, Chapter 10

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Chapter Topics

• Software development process
• Programming languages
• Compilation and link editing
• Interpretation
• Symbolic debugging
• Application development tools

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The Application Development Process

• The process of designing and constructing
  software translates users information processing
  needs into CPU instructions that, when executed,
  address those needs.
• Software development is a complex process that
  requires significant effort and resources. The
  complexity of software development creates many
  possibilities for error.

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The Application Development Process
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The Application Development Process

• Systems Development Life Cycle
• The SDLC breaks the complex process of software
  development into smaller and more management
  pieces.
• The output of each phase of the SDLC produces
  input to the next phase.

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Application Development
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The Application Development Process

• Methodologies and Models
• Developers attempt to minimize errors during the
  SDLC by using proven development methodologies.
• Structured methods document the flow of data or
  the relationship of various processes.
• Object-oriented development models objects and
  classes.

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The Application Development Process

• Tools
• Software development is supported by many
  automated tools.
• Software development tools vary with the target
  system deployment environment.

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The Application Development Process

• Tools
• The declining cost of computer hardware and the
  increasing cost of application development labor
  supports the development of automated system and
  software development tools.
• Which costs more today?

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Programming Languages

• A programming language is a language that is used
  to instruct a computer to perform a task.
• Program instructions are called code.
• Programs are written by a programmer or coder.

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Programming Languages

• Two ways to make programs easier to write and
  applications easier to develop are
• 1. Make the programming language easier for
  people to understand.
• 2. Develop languages and program development
  approaches that require people to write fewer
  instructions.

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Programming Languages
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Programming Languages

• First Generation Languages
• Program are written using machine language.
• Disadvantages
• Difficult for people to remember to code.
• Difficult to find errors.
• Tedious to write program statements.

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Programming Languages

• Second Generation Languages
• Programs are written using assembly language.
• Assembly language uses short mnemonics to
  represent CPU instructions.
• Easier for people to remember and manipulate than
  binary code.
• Must be translated to binary code.

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Programming Languages

• Third Generation Languages
• Examples COBOL, C
• Allow programmers to specify many CPU actions
  with a single program instruction.
• Uses mnemonics to represent instructions,
  variables, and labels.
• Must be translated to binary code.
• Most have significant limitations with respect to
  modern hardware, GUIs and DBMSs.

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Structured Development
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Programming Languages

• Fourth Generation Languages
• Examples VB, SQL
• Instructions or prewritten functions to implement
  interactive and GUIs.
• Instructions to interact directly with an
  internal or external relational databases.
• Ability to describe processing requirements
  without precisely specifying solution procedures.

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Programming Languages

• Fifth Generation Languages
• Nonprocedural language suitable for developing
  software that mimics human intelligence.
• Contains a set of nonprocedural rules that mimic
  rules people use to solve problems.

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O-O Development
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Programming Languages

• Object-Oriented Programming
• Good for program reuse, maintenance
• OOP views data and programs as two parts of an
  object.
• Objects respond to messages without changing the
  data
• Procedures that manipulate the data are called
  methods.
• Only methods can manipulate and change the
  original data.

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Programming Languages
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Programming Languages

• Programming Language Standards define
• Language syntax and grammar.
• Machine behavior for each instruction or
  statement.
• Test programs with expected warnings, errors and
  execution behavior.

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Programming Languages

• Terms to know.
• Instruction explosion
• Procedural which languages?
• Non-procedural can you name one?
• Machine independence

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Compilation

• Data Declarations
• Data Operations
• Control Structures
• Function Calls

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Compilation

• Program Editor used to input the program into
  the computer system. (Source code)
• Compiler translates some source code
  instructions directly into executable code and
  other source code instructions into library
  calls, which are further processed by the Link
  Editor. (Object Code)

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Compilation
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Compilation

• Data Declaration defines the name and data type
  of one or more program variables.

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Compilation

• Data Operations
• Any instruction that updates or computes a data
  value.
• The compiler translates data operation
  instructions into an equivalent sequence of data
  movement and data transformation instructions for
  the target CPU.

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Compilation

• Data Operations
• For Example f_temperature 212

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Compilation

• Control Structures - a source code instruction
  that controls the execution of other source code
  instructions
• Control structures include
• Unconditional branches (Goto statements)
• Conditional branches (If statements)
• Loops

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Compilation

• Unconditional Branch Example
• Source code
• F_temperature 0
• Loop F_temperature F_temperature 1
• Goto Loop
• What happens to the computer if you run this code?

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Compilation

• Compiled Unconditional Branch
• 2000 MOV 1000 lt0gt
• 2004 MOV R2 lt1gt
• 2008 MOV R1 1000
• 200C RADD R1 R2 R1
• 2010 MOV 1000 R1
• 2014 JMP 200C

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Compilation

• Loop Example
• F_temperature 0
• While (F_temperature lt 10)
• F_temperature F_temperature 1

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Compilation

• Conditional Branch Example
• If (c_temperature gt -273.16)
• f_temperature (c_temperature 1.8) 32
• Else
• f_temperature -999

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Compilation

• Function Calls a call instruction transfers
  control to the first instruction in the function
  and the function transfers control to the
  instruction following the call by executing a
  return instruction.

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Compilation

• To implement the call and return instructions,
  the compiler generates CPU instructions to
• Pass input parameters to the function
• Transfer control to the function
• Execute CPU instructions within the function
• Pass output parameters back to the calling module
• Transfer control back to the calling module at
  the statement immediately following the function
  call statement.

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Compilation

• Function Example
• float Fahrenheit_to_Celsius(float F)
• float Cel
• Cel (F 32) / 1.8
• return (Cel)

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Link Editing

• A link editor searches an object code for
  external function calls.
• When an external function call is found, the link
  editor searches other object code files or
  compiler libraries to find executable code that
  implements the function.

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Link Editing

• Benefits of a link editor
• A single executable program can be constructed
  from multiple object code files compiled at
  different times.
• A single compiler can generate executable
  programs that run under multiple operating
  systems.

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Dynamic and Static Linking

• Dynamic Linking linking is performed during
  program loading or execution.
• Static Linking library and other subroutines
  cannot be changed once they are inserted into the
  executable code.

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Dynamic and Static Linking

• Dynamic Linking Advantages
• Smaller application program files
• Flexibility
• Static Linking Advantages
• Execution speed
• Improved reliability and predictability of
  executable programs

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Interpreters

• Read a single source code instruction, translates
  it into CPU instructions or a DLL call on the
  fly.
• Advantage flexibility to incorporate new or
  updated code into an application program.
• Disadvantage increased memory and CPU
  requirements during program execution.

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Interpreters vs. Compilers
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Java
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Whats different about Java?

• Compilation for the Java Virtual Machine
• Translated by the VJM byte code interpreter
• Two types of programs
• Applets in a sandbox
• Stand alone
• How does this compare to native applications?
  Advantages?

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Symbolic Debugging
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Symbolic Debugging

• A symbolic debugger is an automated tool for
  testing executable programs.
• Symbolic debugger features
• Trace calls to specific source code statements or
  subroutines
• Trace changes to variable contents
• Execute source code instructions one at a time
• Detect run-time errors and report them to the
  programmer in terms of specific source code
  instructions and variables

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Integrated Application Development Tools

• Tools are needed during each phase of the SDLC
• Range from simple text editors to massive,
  multiply linked programs

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CASE Tools

• Computer Assisted Software Engineering (CASE)
  tool a tool that supports the SDLC analysis and
  design phases.
• Supports a broad range of system development
  activities with particular emphasis on model
  development.

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Integrated Application Development Tools
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Integrated Application Development Tools

• Programmers Workbenches an integrated set of
  automated support tools to speed development and
  testing.
• Smart program editor
• Compiler and/or interpreter
• Link editor and a large library of classes or
  subroutines

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Integrated Application Development Tools

• Programmers Workbenches cont.
• Interactive facility for prototyping and
  designing user interfaces
• Symbolic debugger
• Integrated window-oriented graphical user
  interface

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Integrated Application Development Tools
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Summary

• Application systems can be developed by following
  the steps of the systems development life cycle.
  (SDLC)
• Executable software consists entirely of CPU
  instructions.
• All programming language generations other than
  the first must be translated into CPU
  instructions prior to execution.

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Summary

• Compiled and interpreted programs must be linked
  to libraries of executable functions or methods.
• Application development is more efficiently
  supposed by integrated suites of automated tools.