Introduction to Computer Software

Introduction to Software

• Software consists of a series of instructions that tells the computer what to do
• Also known as a program, software can be categorized into two major categories: System Software and Application Software

Application Software

• Designed to make users more productive and/or assist with personal tasks
• Examples include:
  • Word processing software (e.g., creating and manipulating documents)
  • Spreadsheet software (e.g., organizing data, performing calculations, and creating charts)
  • Presentation software (e.g., creating visual aids for presentations)

System Software

• Serves as the interface between the user, application software, and the computer's hardware
• Two types of system software are:
  • Operating System (OS)
  • Utility programs

Operating System (OS)

• A set of programs that coordinates all activities among computer hardware devices and allows users to run application software
• Examples of OS include:
  • MS DOS
  • Windows (3.X, 95, 98, ME, 2000, XP, NT, VISTA, 7, 8, 10, 11)
  • Apple operating systems (MAC OS X, iOS)
  • Linux and Unix

Booting Process

• The process of starting or restarting a computer
• Two types of booting processes are:
  • Cold Boot (turning on a computer that has been powered off)
  • Warm Boot (restarting a computer using the operating system)

Classification of OS

• Multi-user: allows two or more users to run programs at the same time
• Multiprocessing: supports running a program on more than one CPU
• Multitasking: allows more than one program to run concurrently
• Multiprogramming: allows different parts of a single program to run concurrently
• Real-time: responds to input instantly

Modes of Processing

• Batch Processing: data is collected and processed at a certain time (e.g., weekly, monthly)
• Online Processing: data is collected and processed immediately, user interacts directly with the computer
• Real-time Processing: inputting, processing, and outputting data continuously (e.g., anti-missile systems, aeroplane landing control system)
• Interactive Processing: simplest way to work on a system, using command line or graphical environment
• Time-sharing Processing: allows many users to use a computer system simultaneously

Components of OS

• Kernel: the main part of the OS, executes processes and handles interruptions
• Scheduler: initiates and terminates jobs, allocates computer resources
• Process Manager: enables processes, allocates resources, and protects resources
• File Manager: manages files and memory
• Shell: interface between the user and the OS, allows user to enter commands

Functions of OS

• Starting a computer
• Providing a user interface
• Managing computer resources
• Managing files and memory
• Maintaining security
• Managing tasks
• Multiprocessing

Process Management

• Allocates time for processes to use the CPU
• Keeps a check on other processes waiting to use the CPU
• Signals when CPU is available

Main Memory Management

• Allocates memory for programs and data
• Uses virtual memory to split large programs into manageable blocks

File Management

• Manages files in secondary storage
• Checks the amount of memory needed for file operations
• Organizes files in secondary storage

I/O System Management

• Manages the flow of information among devices
• Uses buffers to manage devices

Secondary Management

• Manages secondary storage (e.g., disk management)
• Allocates storage space
• Manages disk scheduling

Utility Software

• Supports the OS in housekeeping tasks
• Examples include:
  • Protecting software against damage caused by viruses
  • Making copies of files (back up) software