OPERATING SYSTEMS

Operating System (OS)

A collection of computer programs that integrate hardware resources and make them available to users and programs.

Limitations without an OS

Instructions must be loaded into memory by hand, no user interface, system sits idle waiting for input, no facility for file management.

Interactive OS

Also known as conversational systems, allowing users to interact with the system during execution.

Batch Processing OS

Systems where users submit 'jobs' for processing with little to no interaction during execution.

Event Driven OS

Systems driven by interrupts or specific service requests.

Memory Resident (The Kernel)

Essential services always loaded in memory managing memory, processes, tasks, and storage.

Monolithic Kernel

A large kernel containing all services; requires careful stability management.

Hierarchical Kernel

Organized in layers where requests pass down to layers below.

Microkernel

Provides only minimum essential functionality; services are requested via messages.

Basic OS Services

Critical services that act as an interface between hardware and user.

User Interface in OS

Provides shells and interfaces (CLI or GUI) to accept user commands.

File Management in OS

Provides directory structures and tools to copy, move, and secure files.

Process Control in OS

Manages processes and threads.

Memory Management in OS

Tracks loaded programs, allocates/deallocates memory, prevents overwriting.

Scheduling in OS

Uses dispatching and multitasking to simulate concurrent execution of multiple programs.

Security in OS

Protects the OS and processes from unauthorized entry.

Single-user Systems/Workstations

Standard laptops and desktops (e.g., Windows, macOS, Linux).

Mobile OS

Designed for handheld devices with constraints on power and memory (e.g., iOS, Android).

Mainframe Systems

Designed for large-scale resources and high transaction volumes.

Network Servers

Focused on supporting clients with services like web, file, or database hosting.

Real-time Systems

Require immediate OS access for time-critical tasks.

Embedded Control Systems

Specialized for single pieces of equipment like a microwave or car engine.

Distributed Systems

Processing power spread across a cluster or network.