Glossary of Terms

Access Control

A method used to restrict access to system resources based on user identity or role. Access control determines which users or processes are authorized to access or modify data.

Address Space

The range of memory addresses that a process can use. Each process has its own virtual address space isolated from others.

Asynchronous Signal

A signal delivered to a process at an unpredictable time, often in response to an external event like a keyboard interrupt.

Atomic Operation

An operation that completes without the possibility of interference from other operations. It is indivisible and guarantees consistency.

Background Process

A process running independently of user interaction, typically started with an & in Unix shells.

BSS Segment

A region of memory used to store statically allocated variables that are declared but not initialized. Example: Uninitialized global variables reside in the BSS segment.

Buffer

A temporary storage area used to hold data while it is being transferred between two locations.

Child Process

A process created by another process (the parent) using a system call like fork().

Command-Line Argument

An input value passed to a program at the time of execution, used to control program behavior. Example: ./minitar -c -f archive.tar file1.txt

Condition Variable

A synchronization primitive used to block a thread until a particular condition is met.

Context Switch

The act of saving and restoring the state of a CPU so that execution can switch from one process or thread to another.

CPU Scheduling

The method by which the operating system decides which process or thread should be executed next on the CPU.

Critical Section

A section of code that must be executed by only one thread at a time to prevent race conditions.

Daemon

A background process that runs without user interaction, often initiated at boot time to perform system-level tasks.

Deadlock

A condition where two or more processes are waiting for each other to release resources, resulting in a cycle that prevents progress.

Disk I/O

Operations involving reading from or writing to disk storage.

Dynamic Memory Allocation

The process of allocating memory at runtime using functions like malloc().

Endianness

The byte order used to store data in memory. Common types are little-endian and big-endian.

Environment Variable

A variable that defines system-wide or process-specific settings, accessible via the process's environment.

Error Code

A numeric or symbolic value returned by a function or system call to indicate the outcome of an operation.

Exit Status

A value returned by a process when it terminates, used to signal success or failure to the parent process.

File Descriptor

An integer handle used by the operating system to identify an open file, socket, or pipe.

File Metadata

Attributes of a file such as size, permissions, timestamps, and ownership.

File Pointer

A pointer used to access a specific location in a file, typically used with the fseek() and ftell() functions.

File System

A structure for organizing and storing files on a storage device.

Fork

A system call used to create a new process by duplicating the calling process.

Free

A function used to deallocate memory previously allocated using malloc() or similar functions.

GDB

The GNU Debugger, a tool used to debug C/C++ programs by inspecting variables and controlling program execution.

Header Block

A 512-byte block in a tar archive that stores metadata for a file. Example: fill_tar_header() populates this structure in minitar.

Heap

A region of a process's memory used for dynamic memory allocation.

I/O Redirection

The practice of changing the standard input/output of a command to read from or write to a file.

Inode

A data structure in a Unix file system that stores information about a file except its name.

Interrupt

A signal sent to the CPU to indicate an event that needs immediate attention.

IPC (Inter-Process Communication)

Mechanisms provided by the OS to allow processes to communicate and synchronize.

Kernel

The core component of an operating system responsible for managing hardware and system resources.

Kernel Space

A protected memory region where the operating system kernel executes and manages operations.

Linked List

A dynamic data structure consisting of nodes that contain data and a pointer to the next node.

Listener Socket

A socket that waits for incoming connection requests in a server program.

Load Address

The starting address in memory where a program is loaded.

Lock

A mechanism that prevents concurrent access to a resource by multiple threads.

Makefile

A script used to manage the build process of a project using the make utility. Example: make test runs all automated tests.

Memory Leak

A condition where allocated memory is not properly deallocated, leading to wasted resources.

Memory Mapping

A technique that maps a file or device into memory so that file I/O can be treated as memory operations.

Message Queue

An IPC mechanism for sending and receiving messages between processes.

Minitar

A simplified, POSIX-compliant implementation of the tar utility. Example: minitar can create and extract archive files.

Mode

A file attribute indicating read, write, and execute permissions.

Mount Point

A directory in which an additional file system is attached to the existing directory tree.

Mutex

A mutual exclusion lock used to prevent simultaneous access to a resource.

Named Pipe

A special file that acts as a conduit for communication between processes. Unlike anonymous pipes, named pipes have a name in the file system.

Octal Notation

A base-8 numbering system often used to represent file permissions and tar metadata.

Offset

The position of a byte or block within a file or memory region.

Orphan Process

A process whose parent has terminated, leaving it under the control of the init or systemd process.

Page Fault

An event triggered when a process accesses a part of its address space that is not currently in physical memory.

Page Table

A data structure used by the memory management unit to map virtual addresses to physical addresses.

Parent Process

A process that creates one or more child processes.

Path

A string that specifies the location of a file or directory in the file system hierarchy.

Permissions

Attributes that define the access rights of users to files and directories.

Pipe

A unidirectional communication channel between two processes.

Pointer

A variable that holds the memory address of another variable.

Posix

A family of standards specified by IEEE to maintain compatibility between operating systems. Example: minitar follows the Posix archive format.

Process

An independent execution unit with its own memory space, created using a system call like fork().

Process Table

A data structure maintained by the OS to track all running processes.

Race Condition

An undesirable effect where the outcome of a program depends on the timing of uncontrollable events.

Read System Call

A system call used to read data from a file or input device.

Recursion

A programming technique where a function calls itself to solve smaller sub-problems.

Return Code

A value returned by a function or program indicating success or failure.

Scheduler

The OS component responsible for determining which process/thread runs at any given time.

Semaphore

A synchronization primitive that is used to control access to a common resource in concurrent systems.

Shell

A command-line interpreter that allows users to interact with the operating system.

Signal

A notification sent to a process to inform it of an event. Example: SIGINT interrupts a program from the terminal.

Socket

An endpoint for communication between two machines or processes over a network.

Stack

A region of memory used for function calls, storing return addresses, parameters, and local variables.

Standard Input (stdin)

The default source of input for a program, usually the keyboard.

Standard Output (stdout)

The default destination for output from a program, usually the terminal.

Standard Error (stderr)

The standard output stream used for error messages.

Static Variable

A variable that retains its value across function calls and has a fixed memory location.

Strace

A diagnostic tool that traces system calls made by a process.

Swap Space

Disk space used to supplement RAM by holding inactive pages of memory.

System Call

A request from user space to the operating system to perform a privileged operation.

Tar

A Unix utility that combines multiple files into a single archive. minitar replicates this functionality in a simplified form.

TCP (Transmission Control Protocol)

A reliable, connection-oriented protocol used for transmitting data over networks.

Thread

A lightweight process that shares memory with other threads in the same process.

A method for allowing multiple processes to use the CPU by switching between them quickly.

TLB (Translation Lookaside Buffer)

A cache used to reduce the time taken to access page table entries.

UID (User Identifier)

A numeric value that uniquely identifies a user on a Unix system.

Unnamed Pipe

A pipe created without a name in the file system, typically used for communication between a parent and child process.

Update Operation

A minitar operation that appends new versions of existing files in an archive.

User Space

The portion of memory where user applications run, separate from kernel space.

Virtual Address

An address used by a process that is translated to a physical address by the MMU.

Virtual Memory

An abstraction that allows processes to use more memory than physically available by using disk storage.

Wait

A system call used by a parent process to wait for its child to terminate.

Write System Call

A system call used to write data to a file or output device.

Zero Block

A 512-byte block of zeros marking the end of a tar archive.