Application Software

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Application Software Data

• Davis Rajkumar (6th), Chp. 3

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Overview

• Software
• Absolute vs relative addressing
• Languages
• Layers of abstraction
• Structured software
• Object-oriented software
• Libraries
• API

• Data
• Data elements
• Data structures
• Data files
• Relative records
• Access techniques
• DBMS
• HexMac
• Data
• Machine language

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Software

• Instructions for computer
• Machine instruction
• Opcode and operand
• Binary
• Higher level use words or symbols
• Classifications of software
• Application
• Systems
• Network

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Absolute vs Relative Addressing

• Absolute addressing specifies actual memory
  location
• Relative addressing
• Base addresscan change w/each execution
• Offsetdisplacement from base address

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Languages

• Machine code binary
• Assembler processor dependent
• Mnemonics for opcodes
• Symbolic addresses for variables
• Low level languages C
• Allow bit manipulation
• Permit access to devices
• High level languages COBOL, Pascal, Basic
• Use complex statements
• Limit access to devices and bit manipulations
• Object-oriented Java, C
• Encapsulate data
• Objects have attributes and behaviors

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Programming Process

• Edit
• Source code
• Create program in editor
• Compile or interpret
• Object code
• Convert source code to binary, byte-code, or
  p-code
• Link
• Image
• Incorporate existing modules with object code
• Run
• Load image
• Execute image

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Layers of Abstraction

• Layers
• Applications
• Operating system
• Hardware
• Each layer views processing in more detail
• Applicationinstructions and variables
• Operating systemopcodes and operands
• Hardwarecircuits and pulses

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Alternate System Model

• Specialty layer
• Users, procedures, and macros
• Users data and models of data
• Application layer
• Presentation and business logic software
• Program's view of data
• Infrastructure layer
• DBMS, operating systems, network, hardware
• Processes and system settings

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Structured Software

• Modular
• Hierarchical
• Primary logic
• Secondary logic
• Utilities
• Goal to maximize cohesion and limit coupling
• Cohesioneach route does one thing with local
  data
• Couplingconnection of routines through global or
  control data or spaghetti code

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Object-oriented Software

• Emphasis on entities rather than processes
• Encapsulates data and routines that manipulate
  the data
• Promotes cohesion
• Discourages coupling
• Objects
• Attributes
• Behaviors
• Event-driven
• Objects communicate using messages
• Behaviors triggered by messages from objects or
  operating system

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Libraries

• Collections of code
• Each language has some predefined functions or
  subroutines
• Java's awt, io, and math packages
• Some languages permit development of user
  (programmer) defined libraries
• Riley's aLibrary for Java
• HexMac uses both predefined and user defined
  libraries

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API

• Application Programming Interface
• Used to define programming language or
  programming features
• Source level functions and conventions
• Provide consistent
• Look and feel
• Calling conventions between program and operating
  system

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Data

• Facts or representations of facts
• Subject of processing
• States concerning processing
• Bit patterns manipulated by processors,
  transmitted through buses, and stored in
  registers, memory, or other storage devices

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Data Elements

• Single meaningful unit of data
• Common types for data elements
• Integer
• Float
• Character
• Boolean
• Pointer
• Blobbinary large object
• String is array of characters, but some languages
  treat as data element

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Data Structures

• Combinations of data elements
• Common data structures
• Array
• Linked list and tree
• Stack
• Record
• File

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Data Files

• File
• Collection of records usually with same record
  structure
• Used for storing related facts about group of
  entities
• Recordcollection of fields
• Record structure
• Order of fields
• Data type of fields
• Fielddata element

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Relative Records

• Records have a location in a file
• Location can be absolute or relative
• Absolute location specifies physical address of
  record
• Relative location gives order of record in file,
  such as record one, record two, and so forth

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Access Techniques

• Three types of record access
• Sequential
• Indexed
• Direct or random
• Sequential files
• Read records in order written
• Write records one after another
• Cannot access a record directly
• Direct files
• Use hashing algorithm to write and read records
• Records can be accessed in any order
• Indexed
• Records stored sequential
• Have index for direct access

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DBMS

• Database management system
• Combination of data and software
• Software organizes, stores, retrieves, updates,
  and deletes data
• Models data with respect to its relationships
  with other data in collection
• Special languages used to define (model) data and
  query data

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HexMac

• Data
• Inputhexadecimal only
• Output
• Hexadecimal
• Decimal
• Character
• Machine Language
• Demo

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Summary

• Softwareordered series of instructions
• Application softwareprograms that specialize
  computer
• Operations softwareprograms and utilities that
  manage resources and provide services to
  applications
• Languages used to write software
• Machine
• Assembly
• High level
• Object oriented
• Data
• Subject of computation
• States of computation
• Configuration settings for computations
• Data elementsbasic unit of data
• Data structurecombinations of elements

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Questions?