Operating Systems Overview and Core Concepts

Vocabulary flashcards covering core operating system principles, components, memory management, scheduling algorithms, and architecture classifications.

Operating System (OS)

An interface between computer hardware and the user (programs or humans) that facilitates the execution of other programs and governs access to hardware and software resources.

Bootstrap Program

A small program held in ROM that executes when the computer is turned on to load the operating system from storage into RAM memory.

Batch Operating System

An early operating system developed in the 1950s to control mainframe computers by transferring resources from one job to the next without interactive user intervention.

Multiprogramming

A technique that holds several jobs in memory at the same time and executes them concurrently by allocating available resources.

Time-Sharing System

A system where computer resources are shared among multiple jobs by allocating each job a specific portion of time, providing users the illusion of exclusive access.

Parallel System

A computer system with multiple CPUs on the same machine designed to accomplish tasks in parallel by serving programs or parts of programs simultaneously.

Distributed System

A system in which jobs and resources are shared among multiple distinct computers connected via an internetwork.

Real-Time System

A system designed to execute tasks within specific time constraints, commonly used to monitor, respond to, or control external physical processes and environments.

User Interface (Shell)

A program in the operating system that accepts requests from users or processes and interprets them for the rest of the system.

Monoprogramming

A memory management scheme where only one program can run at a time, occupying the majority of memory while a small portion holds the operating system.

Partitioning

A memory allocation technique that divides main memory into multiple contiguous, variable-length address spaces to contain individual programs.

Paging

A memory management method that divides physical memory into fixed-size units called frames and programs into equal-sized units called pages to eliminate external fragmentation.

Demand Paging

A memory management scheme combining paging and swapping where pages remain in secondary storage and are swapped into memory only when needed by the executing process.

Demand Segmentation

A memory management technique that partitions memory into variable-length, logically related units called segments, managed using a segment table.

Virtual Memory

An architecture where a process's address space is divided into pages and mapped by the operating system from virtual addresses to physical memory addresses.

Program

A nonactive set of instructions stored on a secondary storage medium, such as a disk or tape.

Job

A program from the moment it is selected for execution by the operating system until it finishes running and returns to residing on the disk.

Process

A program in execution that has been loaded into memory and is either executing or waiting for CPU time.

Job Scheduler

The component of the process manager responsible for moving a job from the hold state to the ready state and from the running state to the terminated state.

Process Scheduler

The component of the process manager that moves processes among the ready, running, and waiting states based on CPU readiness, events, and time-slice expirations.

First-Come First-Served (FCFS)

A CPU scheduling algorithm where processes are assigned the CPU strictly in the order in which they arrive.

Shortest Job First (SJF)

A scheduling policy where the scheduler selects the process with the smallest service time among waiting processes of equal priority.

Round-Robin (RR) Scheduling

A preemptive scheduling algorithm that distributes CPU time equally by allocating each process a fixed time interval known as a time quantum or time-slice.

Deadlock

A condition occurring when two or more processes are permanently prevented from continuing because each is holding a resource required by another and waiting for a resource held by the other.

Starvation

A situation where a process is permanently blocked from obtaining required resources due to continuous prioritization of other processes.

Device Manager

The operating system component responsible for the efficient use of input/output devices, device monitoring, queue maintenance, and access policies.

File Manager

The operating system component that oversees file access control, naming conventions, storage allocation, creation, deletion, modification, and archiving.

32-Bit Operating System

An operating system built on CPU registers, address buses, or data buses of 32 bits, allowing a maximum addressable memory capacity of $2^{32}\text{ bytes}$ ($4\text{ GB}$).

64-Bit Operating System

An operating system built on 64-bit architectures capable of addressing up to $2^{64}\text{ bytes}$ ($16\text{ EB}$) of physical or virtual memory.