Introduction to Operating Systems

Study Notes

An operating system (OS) is a software program that manages a computer's hardware and software resources.
It acts as an intermediary between the user and the hardware, enabling efficient and convenient program execution.
The OS is fundamental to the computer system's overall operation, controlling everything from hardware access to application execution.

The OS serves as a control program, overseeing the execution of user programs to ensure proper system behavior.
It manages the allocation of system resources (like the processor, memory, and I/O devices) to different processes.
It acts as a security guard, controlling access to the system and preventing unauthorized users from accessing sensitive data.

Receptionist: The OS handles the user interface, providing the first point of contact when the computer boots up.
Dispatcher: It manages the queue of programs waiting to be processed and activated.
Security Guard: It controls system and file access, preventing unauthorized access and user interference.
Manager: It manages the efficient allocation of system resources, such as processor time, memory, and input/output devices.
Traffic Officer: It coordinates the flow of data and instructions within the system, ensuring efficient communication between processes.
Accountant: It keeps track of resource usage and potentially allocates charges for resources consumed.

When a user saves a document, the following steps occur:
- The user issues a save command in the application program.
- The application signals the OS that the document needs to be saved.
- The OS communicates with the disk device driver to save the document.
- The disk device driver controls the disk drive to write the document.

An OS is designed to meet specific goals, which guide the design process, ensuring the system achieves desired outcomes.
The design choices regarding algorithms and strategies are based on these goals.

The OS is a complex system comprised of many distinct components, each with specific input, output, and functions.

Operating systems for handheld computers are designed to provide a user-friendly interface, making it easy for users to interact with the device and execute programs.
Operating systems can be designed with a focus on convenience, efficiency, or a combination of both.

Depending on their specific functionality and design goals, operating systems can be grouped into different types, such as:
- Operating systems for personal computers.
- Server operating systems.
- Mobile operating systems.
- Embedded operating systems.