Systems Architecture, Fifth Edition

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SCSC 311 Information Systems hardware and
software
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Chapter Goals

• Application development process
• Programming languages
• Program translation software
• Integrated application development software
• Programmers workbenches
• CASE tools

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The Application Development Process

• Application software development is a complex and
  expansive process.
• Translates user requests into machine
  instructions
• Software development bridges two gaps
• Human language to machine language (binary)
• High-level abstraction to low-level detail

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Systems Development Life Cycle (SDLC) Unified
Process (UP)

• Systems development life cycle (SDLC)
• IS professionals follow a series of steps when
  developing an IS
• e.g. Unified Process (UP)
• Business Modeling and Requirements Disciplines
• Design Discipline
• Implementation and Testing Disciplines
• Deployment Discipline

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Methodologies, Models Tools

• Methodology
• Methodology is an integrated collection of
  models, tools, and techniques
• Developers attempt to minimize errors by using
  proven development Methodologies.
• UP is methodology that employs OOA, design and
  deployment models
• e.g., Class diagrams document user and system
  requirements
• Tools
• to support or completely automate software
  development tasks
• e.g., OS, programming language, program
  translator, DBMS, hardware, etc.
• Proper tool selection is a critical

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Chapter Goals

• Application development process
• Programming languages
• Program translation software
• Integrated application development software
• Programmers workbenches
• CASE tools

7
Programming Languages

• Programming languages instruct computer to
  perform a task, a.k.a. code
• Have evolved through several generations
• All but 1GL must be translated into CPU
  instructions prior to execution (compilers and
  interpreters)
• Programmer goals
• Make language easier for people to understand
• Develop languages and development approaches that
  require people to write fewer instructions to
  accomplish a task
• Understand two key terms in programming language
• Instruction explosion (p395)
• Procedural vs. non-procedural (p398)

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Why are there so many different programming
languages?
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1st Generation Languages

• A machine-level programming language. It consists
  of 1s and 0s
• Required programmers to remember binary codes
  that represented each CPU instruction and to
  specify all operands as binary numbers
• Pros Cons
• run very fast and efficiently
• Tedious to program error-prone

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2nd Generation Languages

• Use mnemonics to represent variables (program
  instruction memory address) and labels (data item
  memory address)
• The code can be read and written fairly easily by
  a human
• but it must be converted into binary code by
  compiler in order to run on a computer.
• Pros and Cons
• Easier to manipulate than binary code

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3rd Generation Languages

• Use mnemonics to represent instructions,
  variables, and labels
• Translated with compilers, link editors, and
  interpreters
• Developed before GUIs, database managers, and
  Internet
• e.g. FORTRAN, Basic, Cobol, Pascal, C
• Pros and Cons
• Machine independent
• Have degree of instruction explosion greater than
  11

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4th Generation Languages

• Majority were proprietary
• many were optional components of database
  management systems
• Most support mixture of procedural and
  nonprocedural instructions
• E.g., SQL, VB, etc.

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5th Generation Languages

• Nonprocedural language suitable for developing
  software that mimics human intelligence
• Rule processor accepts a starting state as input
  and iteratively applies rules to achieve a
  solution
• First appeared in 1960s not widely used until
  1980s
• E.g., Lisp, Prolog

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Object-Oriented Programming (OOP) Languages

• View data and programs as two parts of integrated
  whole (object)
• Not clear successors to 5GLs neither
  nonprocedural nor exclusively used for developing
  artificial intelligence
• E.g., Smalltalk, C, Java, C
• Pros and Cons
• Promote reusability and portability of source
  code
• Uniquely suited to developing real-time programs

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Scripting Languages

• Enable programmers to develop applications that
  do most of their work by calling other
  applications and system software
• Evolved from 4GLs, though most now incorporate
  OOP concepts
• E.g., VB Script, JavaScript, PHP
• Pros and Cons
• Enable rapid assembly of application software by
  gluing together capabilities of other programs
• Limited capacity, Slow

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Programming Language Standards (self study)

• Set by ANSI and ISO
• Include definitions of
• Language syntax and grammar
• Machine behavior for each instruction or
  statement
• Test programs with expected warnings, errors, and
  execution behavior
• Guarantee program portability among operating
  systems and application programs

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Chapter Goals

• Application development process
• Programming languages
• Program translation software
• Integrated application development software
• Programmers workbenches
• CASE tools

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Program development

• Program development with a program editor,
  compiler and link editor

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Compiler

• Checks for syntax and other errors issues
  warning or error messages
• Updates internal tables that store information
  about data items and program components
• Generates CPU instructions or library calls to
  carry out the source code instruction

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Four Source Code Instruction Types

• Data declarations
• Data operations
• Control structures
• Function, procedure, or subroutine calls

(Self-study)
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Data Declarations

• Define name and data type of program variables
• Stored in memory allocated by compiler

The compiler updates a symbol table to keep track
of data names, types, and assigned memory
addresses.
(Self-study)
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Data Operations

• Instructions that update or compute a data value
• Translated by compiler into equivalent sequence
  of data movement and data transformation
  instructions
• Compiler refers to entries in symbol table to
  determine source and destination memory addresses
  for data movement instructions
• E.g., f_temperature 212
• f_temperature f_temperature 1

(Self-study)
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Control Structures Function Calls

• Control structures are source code instructions
  that control the execution of other source code
  instructions
• Common thread is transfer of control among CPU
  instructions
• E.g. Conditional branch, loop
• Function calls named instruction sequences
  executed by call instructions
• Transfer control to the instruction following the
  call by executing a return instruction
• E.g.,
• c_temperature fahrenheit_to_celsius(f_temperatur
  e)

(Self-study)
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Implementing Function Call and Return Instructions

• 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
• (This is the same stack operation studied in
  interrupt handling. P231)

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Static v.s. Dynamic Linking

• Statically links external reference calls in
  object code to library functions combines them
  into a single file containing executable code
• Dynamically link external calls by statically
  linking them to an OS service function that loads
  and executes dynamic-link library (DLL) functions
  at run time

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Dynamic Linking vs. Static Linking

• Static linking
• Library and other subroutines cannot be changed
  once inserted into executable code
• Execution speed
• Improves reliability and predictability of
  executable programs
• Dynamic linking
• Performed during program loading or execution
• Smaller application program executable files
• Flexibility

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Key Benefits of Link Editors in Program
Translation

• 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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Interpret vs. Compilation

• Interpreters interleave source code translation,
  link editing, and execution, one source code
  instruction at a time
• Advantage (vs. compilation)
• Provide flexibility to incorporate new or updated
  code into an
• application program (dynamic linking)
• Disadvantage (vs. compilation)
• Increase memory and CPU requirements during
• program execution

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Programming Language Example Java

• OO programming language and program execution
  environment
• Maximizes reliability of applications and
  reusability of existing code
• Has a standardized target machine language JVM
  for Java interpreters and compilers

(self study)
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Features of Java

• Provision of compilers and virtual machines at
  little or no cost
• Incorporation of JVMs into Web browsers
• Increasing development of application software
  that uses a Web browser as primary I/O device
• Ability of Java programs to execute on any
  combination of computer hardware and OS
• Drawback Reduced execution speed due to use of
  interpreted byte codes and OS translation

(self study)
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Symbolic Debugging

• Use of an automated tool for testing executable
  programs to
• Trace calls to specific source code statements or
  subroutines
• Trace changes to variable contents
• Execute source code instructions one at a time
• Detect and report run-time errors to programmer
• Uses symbol table, memory map, and source code
  files to trace memory addresses to specific
  source code statements and variables
• Inserts debugging checkpoints after each source
  code instruction program execution can be paused
• Debugging vs. production/distribution version
• Incorporated directly in most interpreters

(self study)
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Chapter Goals

• Application development process
• Programming languages
• Program translation software
• Integrated application development software
• Programmers workbenches
• CASE tools

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Application Development Tools
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Integrated Application Development Tools
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Programmers Workbench Components

• Programmers Workbench contains
• Smart program editor
• Compiler and/or interpreter
• Link editor and large library of classes or
  subroutines
• Interactive tool for prototyping and designing
  user interfaces
• Symbolic debugger
• Integrated window-oriented GUI
• E.g. NetBean, JBuilder

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CASE Tools

• Computer-Assisted Software Engineering (CASE)
• Front-end CASE tools
• Support development of requirements and design
  models
• Back-end CASE tools
• Generate program source code from models
• E.g. Rational Rose
• By integrating the modeling and development
  environments using the Unified Modeling Language
  (UML), Rational Rose enables all team members to
  develop individually, communicate collaboratively
  and deliver better software.

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