An operating system (OS) is system software that manages a computer's hardware and software resources. It provides the environment in which application software runs and acts as an interface between applications, users, and hardware.
The OS coordinates resources so that programs can operate efficiently and securely. When an application requests a resource, it normally communicates with the OS rather than controlling the hardware directly.
| OS function | What it does |
|---|---|
| Processor management | Schedules processes, allocates processor time, and supports multitasking by switching between processes. |
| Memory management | Allocates RAM to processes, prevents unauthorized access to memory locations, and releases memory when it is no longer needed. It may also manage virtual memory. |
| Peripheral management | Communicates with devices through device drivers and handles input, output, buffering, and interrupts. |
| File management | Organizes files and directories, tracks storage locations, and controls operations such as creating, opening, saving, and deleting files. |
| Security and user management | Authenticates users and controls access through permissions and different privilege levels. |
| User interface | Provides a graphical user interface or command-line interface through which users interact with the system. |
| Error handling | Detects hardware or software errors, records them, and attempts to prevent one failure from disrupting the entire system. |
For example, when a user opens a document, the OS locates the file, checks access permissions, loads the application and data into memory, schedules processor time, and sends output to the display using the appropriate driver.
A common misconception is that the OS is simply the desktop interface. The interface is only one OS function; the OS continues managing processes, memory, files, and devices even when the user is not directly interacting with it.
In an IB exam, a command term such as explain requires both the function and its effect. Do not merely write “the OS manages memory”; explain that it allocates memory to processes, protects memory areas, and releases memory when processes finish.
