Operating system final

What is fixed partitioning?

Memory is split into fixed-size partitions ahead of time.

What is dynamic partitioning?

Partitions are created as needed when processes are loaded.

What is paging?

A process is divided into pages; physical memory is divided into equal-sized frames. Pages map to frames.

What is segmentation?

A process is divided into logical units (segments) of varying sizes.

What is internal fragmentation?

Wasted space inside an allocated memory block.

What is external fragmentation?

Free memory exists, but it's scattered in small holes — no single hole is large enough.

What does compaction do?

Reduces external fragmentation by shuffling memory contents to combine free space into one large block.

What is a page table?

A data structure that maps a page number to a frame number.

What is an inverted page table?

A page table indexed by frame number rather than page number.

What is a page fault?

Occurs when a process accesses a page that is not currently in physical memory — the OS must load it.

What is demand paging?

Only load a page into memory when it is actually needed.

What is prepaging?

Load the needed page plus nearby pages, anticipating future access.

What is the first-fit allocation strategy?

Allocate the first hole that is large enough.

What is the next-fit allocation strategy?

Like first-fit, but the search continues from where the last allocation was made.

What is the best-fit allocation strategy?

Allocate the smallest hole that is large enough

What is local page replacement?

Replace a page belonging to the same process that caused the fault.

What is global page replacement?

Replace a page from any process in memory.

What is a working set?

The set of pages a process is actively using at a given point in time.

What is PFF (Page Fault Frequency)?

A strategy that adjusts a process's memory allocation based on its page fault rate — high rate = give more frames.

What is the difference between a page and a frame?

A page is a fixed-size chunk of a process; a frame is a fixed-size chunk of physical memory. Pages are loaded into frames.

Does paging eliminate external fragmentation?

Yes. Does it eliminate internal fragmentation? No — the last page of a process may not fill its frame completely.

What is a field?

The smallest unit of data (e.g., a single attribute like a name or number).

What is a record?

A collection of related fields.

What is an inode?

A data structure storing a file's metadata (size, permissions, timestamps, pointers to data blocks).

What is a dentry?

A directory entry — maps a file name to its inode.

What is a superblock?

Stores metadata about the entire file system (size, free blocks, etc.).

What is a device driver?

OS-level software that controls a specific hardware device. It is part of the OS

What is logical I/O?

The user/application-level view of I/O (reading records, files).

What is physical I/O?

The actual transfer of bits between memory and a device.

What is contiguous file allocation?

A file is stored in adjacent (contiguous) blocks on disk.

What is a sequential file?

A file where records are accessed in order, one after another.

What is a direct file?

A file where any record/block can be accessed directly by its address.

What is an indexed file?

A file that uses an index structure to locate records.

What is a Type-1 hypervisor?

Runs directly on bare metal hardware — no host OS. Better performance. (e.g., VMware ESXi)

What is a Type-2 hypervisor?

Runs on top of a host OS. Easier to set up, lower performance.

What is Ring 0?

The most privileged CPU execution mode — where the OS kernel runs.

What is Ring 3?

The least privileged mode — where user applications run.

What does DRS do in VMware?

Distributes/balances workloads across hosts in a cluster.

What is Storage VMotion?

Migrates a VM's storage (data) to a different host while the VM is still running.

What is VMware Fault Tolerance?

Keeps a VM running through a hardware failure by maintaining a live shadow copy.

What do Linux capabilities do?

Split the all-or-nothing root privilege into smaller, more granular privileges.