1. Defintion
1.1. programs that acts as an intermediary between a user of a computer and the computer hardware
2. Computer Startup
2.1. Bootstrap Program
2.1.1. first thing that is loaded at reboot
2.1.1.1. ROM
2.1.1.2. EPROM
2.2. bootloader
2.2.1. a small program that places the OS in the memory
3. Interrupter
3.1. Types
3.1.1. Hardware
3.1.2. Software
3.2. Handling
3.2.1. Polling
3.2.2. Vector
4. OS
4.1. resource allocator
4.1.1. Decides between conflicting requests for efficient and fair resource use
4.2. control program
4.2.1. Controls execution of programs to prevent errors and improper use of the computer
5. Protection & Security
5.1. Protection : any mechanism for controlling access of processes or users to resources defined by the OS
5.2. Security : defense of the system against internal and external attacks
6. Computer System
6.1. Structure
6.1.1. User
6.1.1.1. people
6.1.1.2. machines
6.1.1.3. other computers
6.1.2. Application Program
6.1.2.1. which the system resources are used to solve the computing problems of the users
6.1.2.1.1. Google chrome
6.1.2.1.2. Video Games
6.1.2.1.3. Compilers
6.1.3. Operating System
6.1.3.1. controls & coordinates use of hardware among various applications and users
6.1.3.1.1. Windows 10
6.1.3.1.2. Windows 8
6.1.3.1.3. Linux
6.1.4. Hardware
6.1.4.1. provides basic computing resources
6.1.4.1.1. CPU
6.1.4.1.2. memory
6.1.4.1.3. I/O devices
6.2. Architecture
6.2.1. Multiprocessor
6.2.1.1. Asymetric
6.2.1.2. Symmetric
7. Management
7.1. Process
7.2. Memory
7.3. Storage
7.4. Mass-Storage
8. Operations
8.1. Dual-Mode
8.1.1. User
8.1.2. Kernel
9. Structure
9.1. Storage
9.1.1. Main memory
9.1.2. Secondary
9.2. Multiprogramming
9.2.1. 1 job selected & run via job scheduling
9.3. TimeSharing
9.3.1. several jobs ready to un at the same time - CPU scheduling