Introduction to Operating Systems
Introduction to Operating Systems tests the OS as a resource manager: how it schedules processes, allocates memory, organizes files and controls devices. Expect function-matching questions, OS-type identification and GUI versus CLI comparisons.
Core rules and concepts
- The kernel is the privileged core; the shell is the command interpreter users interact with.
- Five core functions: process management, memory management, file management, device management, and security/protection.
- Multiprogramming keeps several jobs in memory; multitasking switches rapidly between tasks; multiprocessing uses two or more CPUs.
- Time-sharing gives each user a time slice; a real-time OS guarantees a response within a deadline.
- Booting loads the OS: cold boot starts from power-off, warm boot restarts a running system.
- A GUI uses windows and icons; a CLI uses typed commands, is faster for scripting but less discoverable.
Worked example
An airbag controller must fire within milliseconds of a crash sensor signal. Choose an OS type. The deciding requirement is a guaranteed worst-case response time, not average speed or user convenience. A time-sharing or batch system may delay the process, so a real-time operating system (RTOS) is correct. If missing the deadline is fatal, it is a hard real-time system; if performance merely degrades, it is soft real-time.
Traps that cost marks
- Treating multitasking and multiprocessing as synonyms; only multiprocessing requires multiple processors.
- Saying the shell is the kernel, or that the kernel is a user application.
- Defining real-time as merely 'very fast' instead of 'deadline-guaranteed'.
- Claiming the OS drives hardware without device drivers.
- Marking Android as a desktop OS; it is a mobile OS built on a Linux kernel.