Key OS Terms · solulu

OS Architecture & Memory Terms

Important concepts in OS design and operation:

System Call: The programmatic way in which a computer program requests a service from the kernel of the operating system it is executed on.
Kernel: The central component of most computer operating systems; it is a bridge between applications and the actual data processing done at the hardware level.
Monolithic kernel: Includes all operating system code in a single executable image.
Micro kernel: Runs minimal performance affecting services; other operations performed by processor.
Macro Kernel: Combination of micro and monolithic kernel.
Re-entrancy : Memory saving technique where multiple users can share a single copy of a program during the same period.
Demand paging: Specifies that if an area of memory is not currently being used, it is swapped to disk.
Virtual memory: Enables processes to execute outside of memory, especially when a program cannot fit in physical memory.
RAID: Redundant Array of Independent Disks, used to store data redundantly to improve performance (7 levels).
Logical address space: Address generated by the CPU. Physical address space: Address seen by the memory unit.

Terms related to OS efficiency and resource management:

Throughput: The number of processes that complete their execution per time unit.
Fragmentation: Memory wastage. Internal (fixed size units) and External (variable size units).
Compaction: A technique to overcome external fragmentation. It involves shifting all the occupied memory blocks to one end of the memory, creating a single large contiguous block of free memory.
Spooling: Data gathered to be used and executed by a device (e.g., printing).
Starvation: Resource management problem where a process doesn’t get resources for a long time.
Aging: Technique used to avoid starvation in the resource scheduling system.
Thrashing: Phenomenon in virtual memory schemes when the processor spends most of its time in swapping pages rather than executing instructions.
Advantages of multithreaded programming: Enhanced responsiveness, resource sharing, economical, utilizes multiprocessing architecture.

The process of starting a computer:

Booting: The process of starting a computer. It can be initiated by hardware such as a button press, or by a software command.
BIOS (Basic Input/Output System): Firmware used to perform hardware initialization during the booting process (power-on startup), and to provide runtime services for operating systems and programs.

Types of user interfaces:

GUI (Graphical User Interface): Allows users to interact with electronic devices through graphical icons and audio indicator such as primary notation, instead of text-based UIs, typed command labels or text navigation.
CLI (Command-Line Interface): Processes commands to a computer program in the form of lines of text.

How data is organized on storage devices:

File System: A method and data structure that the operating system uses to control how data is stored and retrieved.
Directory Structure: The organization of files into a hierarchy of folders (directories). Common structures include Single-Level, Two-Level, Tree-Structured, Acyclic-Graph, and General Graph Directory.