Operating System Fundamentals – Types, Functions, CLI/GUI & OS Structures

These handwritten notes introduce core OS concepts — definition, functions, and types (Batch, Multiprogrammed, Time-Sharing, Multiprocessor, Distributed, Real-Time, Mobile) with diagrams and comparisons. Key comparison tables cover Multitasking vs Multiprogramming, Real-Time vs Time-Sharing, and CLI vs GUI systems. Specific operating systems — DOS, UNIX, Windows, macOS, and Linux — are explained with their architecture, features, and pros/cons. The notes close with the eight Services of an Operating System, Types of System Calls (process, file, device, information, communication), and the five core OS Components (process, memory, file, I/O, and secondary storage management). Clear, exam-ready, and diagram-rich throughout.