Introduction

• Types of software
• System software
• Operating systems
• Application software

Types of computer software

Software Classification

System software

• controls the various components of the hardware
• helps programmers develop applications
• includes the operating system and compilers

Application software

• designed to perform a specific task for a user
• includes word processor, database, spreadsheet…

One way of showing the relationships between them…

Software Categories

Vertical software

• developed for a specific 'type' of client, usually a specialist of some kind (e.g. accountants, doctors, retail outlet)
• may be customisable

Custom software

• written for a specific client

Horizontal software

• designed to be useful for a wide range of users performing varied tasks

System software

• Primarily composed of the operating system
  • manages the hardware (using device drivers)
  • supports applications
  • "hosts" applications
  • may provide a graphical user interface (GUI)
• Provides utilities and services
  • file management
  • backup and restore
  • system maintenance
  • text and image editing

User Interfaces

Text-based interfaces (CLIs)

• Command line: user tpes in specified commands with fixed syntax
• Menu-driven: user chooses from a 'list' of options ('point and shoot')

Graphical user interfaces (GUIs)

• user works with operating system through the GUI
• places special demands on hardware (especially display and memory)
• applications are 'tied' to the interface (how strongly varies with the GUI)
• supports multitasking though use of windows
• may support multiprocessing (multithreading in Windows 95)
• usually combines use of windows, icons, menus and pointers (WIMP)

Operating systems

• The need for an operating system (O/S)
  • in early computers
  • in modern systems
• Characteristics of O/S
  • single tasking vs multitasking
  • interactive vs batch
  • timesharing vs single user

Operating system developments on microcomputers

• Virtual memory
  • provides more memory without extra (costly) RAM
  • requires fast secondary storage
  • essential for multitasking
• Print Spooling
  • form of background processing
  • example of multitasking
• Various forms of cross-platform standardisation

Application software

• Software sold to a "mass market" rather than specialists
  • increasingly includes features previously only found in vertical or custom software
• Needs to provide extensive support for diverse users
  • documentation
  • tutorials
  • demonstrations (videos, animations)
  • help systems
    • general
    • context-sensitive