Short Description

These notes summarize Chapter 2 of the course material based on the textbook Operating Systems Concepts. This chapter delves into the structure of operating systems (OS), focusing on their services, system calls, structure types, and user interfaces such as the command line interpreter. Topics such as microkernels, modular systems, system calls, and APIs are explained in detail.

Operating System Services

The operating system provides a variety of services to users and system processes, which can be categorized as user services and system services.

User Services

  1. User Interface: Interaction with the OS via command-line interface (CLI), graphical user interface (GUI), or touch screen interface.
  2. Program Execution: Loading and running programs, managing program termination.
  3. I/O Operations: Facilitates input and output operations from devices (e.g., reading from a keyboard or writing to a display).
  4. File-System Manipulation: Creation, deletion, reading, and writing of files and directories.
  5. Communications: Enables communication between processes, either on the same machine or over a network.
  6. Error Detection: Monitors and handles hardware and software errors to maintain system reliability.

System Services

  1. Resource Allocation: Efficiently manages system resources like CPU time, memory, and I/O devices.
  2. Accounting: Keeps track of system resource usage for auditing and performance evaluation.
  3. Protection and Security: Ensures that users and processes are properly authenticated and authorized, protecting against malicious activities.

Command Line Interpreter (CLI)

A Command Line Interpreter (CLI), or shell, provides a direct interface for users to enter commands. The CLI fetches a command from the user, executes it, and returns the result.