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Computer Science IGCSEPDF 48
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4.1 Types of Software
Software is a collection of instructions, data, or programs used to operate computers and
perform specific tasks. There are two main types of software:
4.2 Operating Systems (OS)
An Operating System is the most essential system software. It acts as a bridge between the
user/application software and computer hardware.
A. Key Functions of an Operating System
Definition: Software designed to perform specific tasks for the user — solving particular
problems or carrying out a user-defined function.
●
Allocates and tracks RAM usage, ensuring programs don’t
interfere with one another. Uses virtual memory when RAM is full.
● Processor / Task Management (Multitasking): Allocates CPU time using scheduling
methods (round-robin, priority-based) so multiple applications can run.
Definition: Software designed to operate the computer’s hardware and provide a platform for
application software to run. It manages hardware resources and controls system operations.
Examples: Operating Systems (Windows, macOS, Linux), Utility Programs (Antivirus, Disk
Cleanup), Device Drivers.
●
Used for various tasks (Word processors, Spreadsheets,
Web browsers).
● Special-Purpose Software: Performs one specific task (Payroll systems, Ticket
booking).
● Bespoke / Custom-Written Software: Developed for a specific organization’s needs.
● Off-the-Shelf Software: Ready-made, mass-produced for general users (Microsoft
Office, Adobe Photoshop).
A. System Software
B. Application Software
Categories:
General-Purpose Software:
Memory Management: