CS 149 Operating Systems - Vocabulary Review

Vocabulary review flashcards covering C programming basics, process creation, system calls, memory layout, file I/O, IPC, and operating system scheduling concepts.

Kernel Layer

The layer in an operating system model that manages all hardware-dependent functions.

Operating System

A collection of programs that acts as a resource manager, provides a user interface, and handles hardware and software interrupts.

Operating System Model

A three-layer architectural model consisting of the kernel layer, service layer, and user interface layer.

Open Source Operating System

An operating system whose source code is freely available to read and inspect.

Linux Distribution

A custom build or package of the Linux operating system.

main() Function

The mandatory function in a C program that serves as the starting point of execution.

include

A C preprocessor directive that includes standard library header files for input and output before compilation.

include "mylib.h"

A C preprocessor directive that includes a user-defined library header file located in the current working directory before compilation.

define

A C preprocessor directive used to define a symbolic constant or literal that is replaced throughout the source code prior to compilation.

Forward Compatibility

The ability of software or code written under older standards to work with newer standards, or run on newer hardware platforms.

Backward Compatibility

The ability of a system or software standard to remain compatible with older standards or legacy components.

Prefix Increment (++x)

An operator in C that increments the variable $x$ first before returning or evaluating its value within an expression.

Postfix Increment (x++)

An operator in C that evaluates to the current value of variable $x$ first, then increments $x$ by $1$.

fork()

A Unix system call that creates a new child process that is a duplicate (clone) of the calling parent process.

exec System Call

A Unix system call (such as execlp) that transforms an executable binary file into a process by replacing the current process image.

getpid()

A system call that returns the process identifier (PID) of the current calling process.

wait()

A system call used by a parent process to suspend execution until a child process terminates, returning the child's process ID.

Process

A program in execution; it serves as the active unit of work in an operating system.

Program

A passive collection or group of instructions stored on disk designed to perform a specified task.

Stack Frame

A section of memory allocated on the stack at runtime storing temporary data such as function parameters, return addresses, and local variables.

Process Control Block (PCB)

A key data structure maintained by the kernel containing essential information about a process, such as its execution state and stored CPU register content.

System Call

A routine built into the operating system kernel that performs basic, privileged functions on behalf of user applications.

User Mode

The CPU execution mode in which user applications run, restricting direct access to hardware and system resources.

Kernel Mode

The privileged execution mode in which the operating system kernel executes with full hardware access.

lseek()

A system call used for positioning or repositioning the read/write offset pointer of an open file descriptor.

File Descriptor Table

A per-process data structure maintained in kernel memory that maps file descriptors to open file table entries.

Vnode Table

An in-memory kernel data structure (also called the virtual node table or inode table) that stores metadata about an open file.

Inter-Process Communication (IPC)

Mechanisms provided by the kernel and operating system that enable distinct processes to exchange data and communicate.

Pipe

An in-memory kernel buffer data structure used for unidirectional inter-process communication between processes.

Ready State

The state of a process when it is residing in main memory and available for execution by the CPU scheduler.

Blocked State

The state of a process when it is residing in main memory awaiting an event or I/O completion.

Running State

The state of a process whose instructions are currently executing on the processor.

First-Come-First-Served (FCFS)

A non-preemptive job scheduling policy where processes are executed strictly in the order of their arrival in the ready queue.

Round Robin

A scheduling algorithm effective in general-purpose time-sharing systems that assigns a fixed CPU time quantum to each process cyclically.

Multilevel Feedback Queue

A process scheduling algorithm that classifies processes into distinct priority queues and allows them to move between queues.

sigaction()

A POSIX function used to establish or modify a signal handler routine for one or more signals.

kill System Call

A system call in UNIX used to send signals to processes.