Operating Systems: Memory Management and File Systems

Dynamic relocation occurs when the mapping from virtual to physical addresses is performed at runtime, allowing programs to be moved in memory during execution.

Position-independent code (PIC) is machine code that executes correctly regardless of its absolute address in memory, which is essential for shared libraries.

In paging, physical memory is divided into fixed-size blocks called frames, while the logical address space is divided into blocks of the same size called pages.

Physical addresses are the actual addresses in the memory hardware (RAM) that the CPU uses to access data.

Dynamic relocation is performed at runtime, meaning the address mapping can change while the process is running.

Virtual addresses are generated by the CPU and used by the process to reference memory, which are then translated into physical addresses.

The buddy system is a memory allocation algorithm that divides memory into partitions to try to satisfy a memory request as suitably as possible, allowing for easy merging of free blocks.

Static relocation occurs when the addresses are bound to physical memory at load time, meaning the program cannot be moved once execution begins.

Paging allows a process to be stored in non-contiguous physical memory frames, eliminating the need for a single large contiguous block of memory.

In segmentation, a segment descriptor table holds the base address, limit, and access rights for each segment of a process.

The optimal page replacement algorithm (or Belady's algorithm) replaces the page that will not be used for the longest period of time in the future.

A page table is the data structure used by an operating system in a virtual memory system to store the mapping between virtual addresses and physical addresses.

The Least Recently Used (LRU) algorithm replaces the page that has not been accessed for the longest time, based on the principle of locality.

First-In-First-Out (FIFO) is a simple page replacement algorithm that replaces the page that has been in memory the longest.

In paging, the virtual address space is divided into fixed-size blocks called pages, which correspond to physical frames.

A file is the standard unit of storage for logically related data on secondary storage devices.

A flat directory structure is one where all files are located in the same directory, meaning there is only one level of organization.

A single-level directory system is commonly referred to as a flat directory structure because it lacks sub-directories.

A hierarchical directory structure allows users to create sub-directories, enabling a tree-like organization of files.

On a magnetic disk, data is organized into concentric circles known as tracks.

Each track on a disk is divided into smaller segments called sectors, which are the smallest addressable units of storage.

A cylinder is a collection of all tracks that are at the same radial distance from the center across all surfaces of a disk pack.

Fixed-head disks have a dedicated read/write head for every track, which eliminates the seek time required to move a head to a specific track.

Moving head disks, such as standard hard disk drives, use an actuator arm to position read/write heads over specific tracks. Fixed head disks use a dedicated head for every track, which is a different architecture.

Rotational latency specifically refers to the time required for the desired sector to rotate under the read/write head after the head is positioned over the correct track. This is a component of total access time, which also includes seek time and any controller overhead.