Computer Systems, Operating Systems, and Software: Key Concepts for IT Students

Components of a computer system

Hardware, software, and users.

IPOS cycle

Input → Processing → Output → Storage.

True/False: A computer system is just hardware and software.

False — it also includes users.

Examples of peripheral devices

printer, keyboard, mouse, monitor, external drive.

Short-term vs. long-term storage: which is volatile?

Short-term (main memory/RAM) is volatile; long-term (disk/SSD) is non-volatile.

What does a system administrator do?

Installs, configures, maintains, and supports systems, including user training and documentation.

What does a network administrator do?

Designs, configures, and maintains networks (LAN/WAN), addressing, routing, and connectivity.

What is 'software' and its two broad forms?

Programs that run on hardware; system software (OS, utilities) and application software.

Example of how a change at one layer of a socio-technical system can ripple to others

New regulation (society) → change to business processes → updates to application software → OS/config changes.

True/False: Most people who work in IT must have a 4‑year IT degree.

False — many paths exist; roles are diverse.

What is the motherboard?

The main circuit board that houses the CPU, memory, and expansion components.

Define 'storage capacity'

The amount of data that can be stored on a device or medium (e.g., bytes, GB, TB).

Give two responsibilities of a security administrator

Managing firewalls and access controls; monitoring security events and enforcing policies.

What is a MODEM used for?

Modulation/demodulation to send digital data over analog channels.

Define 'application system' in a socio-technical stack

Applications that implement business processes and interact with users and other layers.

Fill-in: The system unit houses the CPU and memory on the ________.

Motherboard.

Define an operating system (OS)

System software that manages hardware, provides services, and runs programs.

Kernel vs. shell

Kernel manages resources at a low level; shell is a user interface (CLI or GUI) to the OS.

Program vs. process

Program = passive code on disk; Process = active instance of a program in execution with state.

Define context switch

The CPU saves one process's state and loads another's, switching execution.

True/False: The OS is hardware.

False — the OS is software.

Competitive (preemptive) multitasking means...

A timer interrupt preempts processes periodically to switch among them.

What data structure maps virtual pages to physical frames?

The page table.

Define a page fault

An event when a referenced virtual page is not in RAM, requiring it to be loaded from disk.

Virtual memory enables...

Programs to use address spaces larger than physical RAM via paging.

Swapping is...

Moving process memory between RAM and disk to free RAM.

Device driver

Software that lets the OS talk to hardware devices like printers or keyboards.

Role: protection vs. security

Protection: mechanisms to control access; Security: broader policies/practices for safeguarding systems.

File permissions are part of which OS role?

Protection.

True/False: 'Process' and 'program' are interchangeable terms.

False — program ≠ process.

Name four major OS responsibilities

Process management, memory management, file systems, I/O devices (plus networking, protection).

CPU scheduling purpose

To decide which ready process runs next on the CPU.

Interrupt

A hardware or software signal that causes the CPU to stop current execution and run a handler.

Ready queue

The set of processes that are ready to run but waiting for CPU time.

Atomic operation

An operation that runs completely or not at all; can’t be interrupted.

Critical section problem is about...

Coordinating access to shared data to avoid race conditions.

Program counter

holds the address of the next instruction; part of the saved state, but doesn’t cause context switches.

Page table

Maps a program’s virtual addresses to physical memory locations.

Context switch

When the CPU saves one process’s state and loads another’s, allowing multitasking between programs.

CLI vs. GUI

CLI accepts text commands; GUI uses windows, icons, menus, and pointers.

File allocation table / inode map

A system map that shows where each file’s data is stored on the disk so the OS can find and read it.

Memory management goal

Allocate RAM fairly/efficiently, isolate processes, and support virtual memory.

System call

A controlled interface by which a program requests a service from the OS.

Protection

Rules in the operating system that control who or what can access files, memory, or devices.

Compilation vs. interpretation

Compilation translates source to machine code ahead of time; interpretation executes source step-by-step via an interpreter.

High-level vs. low-level language

High-level is human-friendly (e.g., Python, Java); low-level is close to machine (assembly).

Algorithm

A step-by-step, finite procedure to solve a problem.

Pseudocode purpose

Express algorithmic steps in structured, language-agnostic form.

Variable

A named storage location with a type and value.

Compiler output

Object/machine code (and possibly intermediate files) for the target platform.

Runtime error vs. compile-time error

Compile-time: detected by the compiler; Runtime: occurs during execution (e.g., divide-by-zero).

Scripting language example

Bash, PowerShell, Python, JavaScript.

Control structures

Sequence, selection (if/else/switch), and iteration (for/while).

Function/procedure

A named block of code that can be called with arguments and may return a value.

Structured programming

Programming style from 1970s using sequence, selection, and loops for clarity.

Object-oriented programming core concepts

Encapsulation, abstraction, inheritance, polymorphism.

Source code management purpose

Track changes, collaborate, and manage versions (e.g., Git).

Debugger

Lets you step through code, inspect variables, and set breakpoints to find bugs.

Unit testing

Testing individual components in isolation to ensure correctness.

Compilation

Translating human-readable code to machine code.

IPv4 address length

32 bits (four octets).

Octet

An 8-bit byte; IPv4 addresses have 4 octets separated by dots.

Subnet mask

Identifies the network vs. host portion of an IP address.

Default route purpose

Where packets are sent when no specific route is known (usually a router/gateway).

LAN vs. WAN

LAN = local area network (campus/office/home); WAN = wide area network (large geographic).

Bandwidth vs. latency

Bandwidth is capacity (throughput); latency is delay (time to deliver).

Role of a router

Connects different networks and forwards packets between them.

Role of a switch

Connects devices within a LAN and forwards frames based on MAC addresses.

DNS purpose

Translates human-readable domain names to IP addresses.

TCP vs. UDP

TCP is connection-oriented and reliable; UDP is connectionless and best-effort.

NAT purpose

Maps private internal IPs to a public IP for Internet access.

CIDR notation example

255.255.255.0 = /24 (first 24 bits are network)

Port number

Endpoint identifier for transport-layer services on a host (e.g., HTTP 80, HTTPS 443).

ARP

Resolves IP addresses to MAC addresses on a LAN.

Ping

Tests connectivity and round-trip time to a host.

Traceroute

Shows the path (hops/routers) a packet takes to reach a destination.

DHCP

Provides automatic IP settings: address, mask, gateway, DNS.

Private IPv4 ranges

10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16.

Loopback IPv4 address

127.0.0.1.

Applying a netmask with AND yields the ________ address.

Network.

True/False: If two devices have different network addresses, they must use a router to talk.

True.

True/False: DNS translates IP addresses into MAC addresses.

False — ARP maps IP→MAC; DNS maps name→IP.

Broadcast in IPv4

Packet sent to all hosts on the local network (e.g., 192.168.1.255 with /24).

Database vs. DBMS

Database: organized collection of data; DBMS: software to create, read, update, and manage databases.

Table/row/column meanings

Table = relation; row = record/tuple; column = attribute/field.

Primary key

A column (or set) whose values uniquely identify each row.

Foreign key

A column in one table that references the primary key of another table.

Normalization purpose

Reduce redundancy and update anomalies by structuring tables into normal forms.

SQL SELECT

Query to retrieve columns from one or more tables with optional filtering and joins.

JOIN

Combines rows from two tables using a shared column (key).

Index

Auxiliary data structure that accelerates lookups for specific columns.

Transaction

A unit of work that is atomic, consistent, isolated, and durable (ACID).

View

A virtual table defined by a query.

Schema

The structure of the database: tables, columns, data types, relationships.

Integrity constraint example

NOT NULL, UNIQUE, PRIMARY KEY, FOREIGN KEY, CHECK.

True/False: A table can have multiple primary keys.

False — only one primary key (but it may be composite).

True/False: A foreign key must match values in the referenced primary key or be NULL (if allowed).

True.

A ________ key uniquely identifies a row.

Primary.

A ________ key references a primary key in another table.

Foreign.

Which file lists currently mounted file systems in Linux?

/etc/mtab.