Introduction to Computer Systems: Software Overview

Introduction to Computer Systems: Computer Software

• Lecture 3 focuses on computer software

Objectives

• Learn different types of software and their purposes
• Understand the operating system's function and types
• Differentiate between generations of programming languages

Computer Software

• Programs execute on hardware
• Program: a set of instructions to complete a task
• Categorized into system software and application software
  • System software: examples include operating systems
  • Application software: examples include web browsers

Types of Software

• Application software is used by users for specific tasks
• System software provides the basic functions performed by the computer.

System Software

• Provides fundamental functions to the computer
• Controls computer hardware
• Acts as an interface between users, application software, and hardware
• Categorized by function:
  • Management (BIOS, OS, Device Drivers, System Utilities)
  • Development (Compiler, Interpreter, Linker)

Operating System

• A special program automatically loaded when a computer starts
• Allows application software and users to interact with hardware without needing detailed hardware knowledge
• Manages and controls computer hardware resources
• A large and complex software with various components
• Examples include Windows, Android, Linux, and UNIX

Operating System Functions

• Process management
• Memory management
• File management
• Device management
• Protection and security
• User interface (or command interpreter)

Operating System Interfaces

• Command line interface (DOS, Unix)
• Graphical user interface (GUI)

Operating System Types

• Single-user, single-task (Palm OS, MS-DOS)
• Single-user, multi-tasking (MS-Windows)
• Multi-user, multi-tasking (UNIX)
• Multiprocessing (UNIX)
• Real-time (RTOS): for real-time applications (e.g., LynxOS)
• Embedded: used in appliances (e.g., microwaves, washing machines, traffic control systems)

System Software Utilities

• Device drivers
• Anti-virus
• Data and disk compression
• Cryptographic
• Disk cleaners
• Backup
• System profiling
• Network managers

Programming Languages

• A set of vocabulary and grammatical rules to express computations and tasks for the computer
• Categories:
  • Machine language
  • Assembly language
  • High-level languages (HLL)

Translator Software

• Assembler
• Compiler: translates an entire program at once; compiled programs execute faster (e.g., C++, Java)
• Interpreter: translates one line at a time; interpreted programs are easier to debug (e.g., Python, some BASIC versions.)

Program Execution Hierarchy

• Source code is translated by a compiler into object code.
• Other object code is combined with the object code by a linker.
• This produces executable code, which is machine language.

Application Software

• Programs designed for specific tasks or general purposes by users
• General Purpose (Word Processing, Spreadsheet, Image Processing, Suite of Software, CAD/CAM, GIS, Web Browser)
• Specialized (Problem-Specific programs, narrow focus on specific disciplines and occupations)

Software Acquisition

• Retail software: sold in stores
• OEM software: bundled with hardware
• Demo software: restricted version for demonstration
• Shareware: free trial period
• Freeware: free for personal use
• Public Domain software: free with no copyright restrictions
• Open-source software: source code is available for customization and alteration.