CS-150 Operating Systems – Vocabulary Flashcards

A comprehensive set of vocabulary flashcards covering operating-system fundamentals discussed in the CS-150 lecture, including OS roles, process and memory management, CPU scheduling, paging, file systems, and directory structures.

Application Software

Programs written to solve specific real-world problems for a user.

System Software

Software that manages a computer system at a fundamental level.

Operating System (OS)

The central piece of system software that manages hardware resources, provides user and program interfaces, and coordinates all other software.

Process

A program that is currently being executed by the computer.

Process Management

The OS activity that tracks, schedules, and controls all active processes.

CPU Scheduling

Selecting which ready process should be moved to the running state and given the CPU.

Single-tasking Operating System

An OS that can execute only one program at a time.

Multi-tasking Operating System

An OS that allows several programs to run concurrently.

Single-user Operating System

An OS that supports one user at a time even if multiple programs run.

Multi-user Operating System

An OS that supports multiple users, associating processes and resources with specific user accounts.

Distributed Operating System

An OS that makes several networked computers appear as one unified system.

Embedded Operating System

A small, specialized OS designed for devices with limited resources.

Real-time Operating System

An OS that guarantees responses within hard time bounds for control or monitoring tasks.

Batch Processing

Executing a group of jobs sequentially without further user interaction.

Time-sharing

Allocating short CPU time slices to many users to give the illusion of dedicated machines.

Multi-processor Environment

Distributing processes across two or more CPU cores or processors.

Process State

The current condition of a process (ready, running, blocked, etc.) during its lifecycle.

Process Creation

The act of starting a new process, either by the OS or by another running process.

Child Process

A new process created by another (parent) process.

Process Termination

The ending of a process due to completion, error, logout, or system shutdown.

Process Suspension

Temporarily halting a process, often to free resources or await an event.

Process Control Block (PCB)

OS data structure that stores all information needed to manage a particular process.

Context Switch

The saving of a running process’s state and loading of another’s so the CPU can switch processes.

Thread

A lightweight unit of execution within a process that has its own context but shares memory.

Non-pre-emptive Scheduling

A policy where the running process keeps the CPU until it voluntarily releases it.

Pre-emptive Scheduling

A policy where the OS may forcibly move the CPU from one process to another.

First-Come, First-Served (FCFS)

A scheduling algorithm that runs processes in the order they arrive.

Shortest Job Next (SJN)

A scheduling algorithm that selects the ready process with the shortest estimated runtime.

Round Robin Scheduling

A pre-emptive algorithm that cycles through processes, giving each a fixed time slice.

Turnaround Time

Total time from a process’s arrival in the ready state to its completion.

Percent Delay

(Turnaround – Service Time) ÷ Service Time × 100; measures scheduling overhead.

Processor Utilization

Percentage of time the CPU performs useful work rather than idling.

Memory Management

OS techniques that track and allocate main memory to processes safely and efficiently.

Logical Address

An address used in program code, expressed relative to the process’s own space.

Physical Address

The actual location in main memory where data or instructions reside.

Process Isolation

Keeping each process’s memory separate so they cannot interfere with each other.

Single Contiguous Memory Management

A scheme with only the OS and one application in memory at once.

Address Binding

Translating logical addresses to physical addresses during program execution.

Base Register

CPU register holding the starting physical address of the current partition or program.

Bounds (Limit) Register

Register holding the size of the current partition; used for address validity checks.

Partition Memory Management

Dividing memory into regions (partitions) to hold multiple processes simultaneously.

Fixed Partition Scheme

Memory is split into a predetermined set of partitions of fixed sizes.

Dynamic Partition Scheme

Partitions are created on the fly to fit program sizes exactly.

Best-Fit Allocation

Choosing the smallest free partition large enough for a program.

First-Fit Allocation

Choosing the first free partition encountered that is large enough.

Next-Fit Allocation

Continuing the search for a free partition from the last allocation point forward.

Worst-Fit Allocation

Choosing the largest available partition for a program (mainly for dynamic partitions).

Fragmentation

Unusable memory created when free space is broken into small pieces.

Internal Fragmentation

Wasted space inside an allocated partition because it is larger than requested.

External Fragmentation

Total free memory is adequate but split into many small non-contiguous blocks.

Paged Memory Management

Dividing processes into equal-size pages loaded into equally sized frames in memory.

Page

A fixed-size block of a process under paged memory management.

Frame

A fixed-size block of main memory that can hold one page.

Page Management Table (PMT)

Per-process table mapping each page to its frame location.

Demand Paging

Loading pages into memory only when they are actually referenced.

Page Swap

Bringing a page into memory and (usually) writing another page back to disk.

Virtual Memory

The illusion of a large address space because an entire process need not reside in RAM.

Thrashing

Severe performance loss caused by excessive page swapping.

File

A named collection of related data stored on secondary memory.

File System

The OS’s logical organization and management of files and directories.

Directory

A named group (folder) that contains files or other directories.

Text File

File containing human-readable characters (ASCII or Unicode).

Binary File

File storing data in non-textual form, requiring specific programs to read it.

File Type

The kind of information a file stores, such as image or audio.

File Format

The internal structure defining how data is stored in a file.

File Extension

The part of a filename after the last dot indicating its type/format (e.g., .txt, .jpg).

Sequential Access

Retrieving file content strictly in order from beginning to end.

Direct Access

Retrieving data from arbitrary locations within a file using an address or offset.

File Protection

Mechanisms that control which users can access a file and how.

Directory Tree

A hierarchical structure showing nested directories and files.

Root Directory

The top-level directory in a directory tree.

Parent Directory

The directory that directly contains another directory or file.

Subdirectory

A directory contained within another directory.

Working Directory

The directory in which a user or process is currently operating.

Path

A textual description of a file or directory’s location in the tree.

Absolute Path

A path that starts at the root directory.

Relative Path

A path that starts from the current working directory.