INFO1112 OS and Network Platforms Study Guide Flashcards

A comprehensive collection of vocabulary flashcards covering key topics from INFO1112 (Computing 1B), including binary representation, machine instructions, Unix shell, user permissions, virtualization, processes, system calls, and Docker.

Binary System

A base-$2$ positional number system using two symbols ($0$ and $1$) that serves as the native representation for computers because physical hardware distinguishes two states (on/off).

Hexadecimal System

A base-$16$ positional number system using $16$ symbols ($0\text{--}9$ and $\text{A\text{--}F}$) used as a compact shorthand for binary where each hex digit maps to exactly $4$ bits.

Byte-Addressable Memory

A memory layout where every byte ($8$ bits), rather than every bit, possesses its own unique address.

ASCII

American Standard Code for Information Interchange; a character encoding scheme that uses $7$ bits per character to represent values from $0$ to $127$.

Unicode

An international character encoding standard created in $1991$ using up to $32$ bits ($4$ bytes) per character, designed to universally represent writing systems, historical scripts, and emoji.

Opcode

The portion of a machine instruction bit pattern that specifies which operation the CPU is to perform.

Operand

The portion of a machine instruction bit pattern that specifies the data value or target memory address to be operated on.

System Mode

A hardware-enforced privileged execution mode (also called kernel mode) that grants the operating system kernel unrestricted access to hardware and instructions.

User Mode

An unprivileged CPU execution mode in which user applications run, preventing direct access to physical hardware or system memory.

System Call

A special CPU instruction that switches execution from user mode to system mode so the kernel can execute a privileged operation on behalf of an application.

Absolute Path

A file pathname that specifies a location starting directly from the root directory ($/$).

Relative Path

A file pathname that specifies a location relative to the current working directory.

Shell

A command interpreter program (such as bash) that reads typed character input, interprets commands, and executes corresponding programs.

Arithmetic Expansion Syntax Bash

The shell syntax $\$(( \text{expr} ))$ that evaluates integer arithmetic expressions and substitutes the computed numeric result into a string.

Redirection Operator >

A shell operator that redirects standard output to a specified file, creating the file if missing or overwriting its existing contents.

Redirection Operator >>

A shell operator that redirects standard output to a specified file, appending content to the end of the file without overwriting existing data.

Pipe Operator |

A shell operator that connects the standard output ($\text{stdout}$) of the left command directly into the standard input ($\text{stdin}$) of the right command.

Shebang

The initial line of a shell script (e.g., $\text{\#!/bin/bash}$) that tells the operating system which interpreter binary to run the script with.

UID (User Identification Number)

A numeric identifier used by the Unix kernel to track process identity, file ownership, and access permissions.

GID (Group ID)

A numeric identifier used by Unix to group multiple users together for managing permissions across many users simultaneously.

Superuser (root)

The administrative account assigned $\text{UID } 0$ that possesses unrestricted authority to access all files, execute any program, control devices, and terminate any process.

/etc/passwd

A colon-separated system configuration file mapping usernames to UID, primary GID, comment, home directory, and default shell.

/etc/group

A system configuration file mapping GID numbers to group names and listing additional member usernames for each group.

Device File

A special file in the Unix filesystem namespace (such as $/dev/sda$) through which hardware devices are accessed using standard file operations.

Right Shift >>

A bitwise operation that shifts bits $N$ positions to the right, discarding bits that fall off the edge and filling vacant positions on the left with zeros.

Bitwise AND &

A bitwise operator that yields $1$ only when both corresponding input bits are $1$, commonly used with a mask to isolate specific bit fields.

Emulator

A software application that reads, decodes, and carries out binary machine instructions by simulating CPU registers and operations without physical target hardware.

Virtual Machine (VM)

A complete system-level emulation managed by a hypervisor that emulates physical hardware (CPU, memory, I/O) to execute a full separate guest operating system.

Hypervisor

A software layer (such as VirtualBox) that creates, manages, and executes one or more virtual machines on top of a host operating system and physical hardware.

Container

An isolated environment with its own processes, network interfaces, and mounts that shares the underlying host operating system kernel rather than running a separate guest OS.

Process

A program in execution, consisting of code and data loaded into memory alongside OS tracking metadata such as PID, UID, and open file descriptors.

fork

A Unix system call that creates a new child process as an exact duplicate copy of the calling parent process, returning $0$ in the child and the child's PID in the parent.

exec

A family of Unix system calls that completely replaces the memory image and code of the calling process with a new program.

wait - UNIX Syntax

A Unix system call that suspends the calling parent process until one of its child processes exits, returning that child's PID.

Zombie Process

A child process that has exited execution but remains in the process table because its parent process has not yet called $\text{wait}$.

kill

A Unix command and system call used to send a signal (defaulting to $\text{TERM}$) to a target process owned by the same UID or by the superuser.

Docker Image

A static, read-only package containing application source code, environment configurations, dependencies, and file structures required to run an application.

Docker Container

A live, runnable, isolated instance created from a Docker Image that virtualizes the OS application layer while sharing the host OS kernel.

Docker Desktop

A software application for Windows and macOS that runs a lightweight hypervisor-managed Linux distribution to supply the Linux kernel required by Linux Docker containers.

docker run

A Docker CLI command that creates and starts a brand-new container instance from a specified Docker image.

docker start

A Docker CLI command that restarts and reuses an existing, stopped container rather than creating a new container instance.