Prelim Exam Study Notes

Operating System

System software that manages computer hardware and software resources and provides services for application programs.

Operating System

It acts as an intermediary between users, applications, and hardware. Common examples include Microsoft Windows, Linux distributions, Android, macOS, and operating systems used in networking equipment. 

Process Management

Creates, schedules, synchronizes, and terminates processes.

Memory Management

allocates and releases RAM and keeps track of memory usage. 

File Management

Creates, organizes, reads, writes, and protects files and directories. 

Device Management

Controls hardware devices through device drivers. 

Security and Protection

controls access to resources, accounts, and data. 

Networking

Supports communication between computers and network resources. 

User Interface

Provides graphical interfaces or command-line environments. 

Error Detection

Identifies and handles hardware and software errors. 

Resource Allocation

Distributes CPU time, memory, storage, and devices among programs. 

Batch Operating System

Executes jobs in groups with little or no direct user interaction. 

Time-Sharing Operating System

Allows multiple users or programs to share CPU time. 

Distributed Operating System

Coordinates resources across multiple networked computers.

Network Operating System

Provides services for network users and devices. 

Real-Time Operating System

Responds to events within strict timing requirements.

Mobile Operating System

Designed for smartphones and tablets, such as Android and iOS.

Embedded Operating System

Designed for specialized devices such as appliances, vehicles, and controllers. 

Kernel

The core of the operating system responsible for controlling hardware and essential system resources. 

Shell

A command interpreter through which users can interact with the operating system. 

Device Drivers

Software that allows the OS to communicate with hardware. 

File System

Organizes and stores files and directories.

System Calls

Interfaces that allow programs to request operating-system services. 

Red Hat Enterprise Linux (RHEL)

An enterprise Linux operating system developed by Red Hat.

Red Hat Enterprise Linux (RHEL)

It is widely used for servers, enterprise applications, cloud environments, virtualization, and infrastructure management.

RHEL

Based on open-source Linux technology and emphasizes stability, security, administration, and long-term enterprise support.

Key Features of RHEL

pwd

displays the current directory. 

ls

Lists files and directories. 

cd

changes the current directory.

mkdir

creates a directory. 

cp

copies files or directories. 

mv

moves or renames files. 

rm

removes files or directories.

cat

displays file contents. 

grep

searches text. 

ps

displays process information. 

top

monitors running processes. 

systemctl

manages system services. 

dnf

installs, updates, and removes packages. 

chmod

changes file permissions.

chown

changes file ownership.

Users and Groups

Accounts are organized to control access to resources. 

Permissions

Read, write, and execute permissions determine what users can do. 

Services

background programs can be started, stopped, enabled, or disabled. 

Logs

system events are recorded for troubleshooting and security monitoring.

Networking

Administrators configure interfaces, IP addresses, routing, DNS, and firewall rules. 

Cisco IOS (Internetwork Operating System)

The operating system traditionally used on many Cisco routers and switches.

Cisco IOS (Internetwork Operating System)

It provides the command-line interface and software functions needed to configure, manage, secure, and troubleshoot networking devices.

User EXEC Mode

basic monitoring commands are available. Prompt commonly ends with >. 

Privileged EXEC Mode

provides higher-level monitoring and administrative commands. Prompt commonly ends with #. 

Global Configuration Mode

used to change device-wide configuration. 

Interface Configuration Mode

used to configure a particular network interface. 

Line Configuration Mode

used to configure console, auxiliary, or virtual terminal lines. 

enable

enters privileged EXEC mode. 

configure terminal

enters global configuration mode. 

hostname

changes the device hostname. 

show running-config

displays the active configuration.

show startup-config

displays the saved configuration. 

show ip interface brief

summarizes interface status and IP addresses.

interface

selects an interface for configuration. 

ip address

assigns an IP address and subnet mask. 

no shutdown

enables an interface. 

copy running-config startup-config

saves the running configuration. 

ping

tests network connectivity.

traceroute

helps identify the path to a destination. 

Basic Configuration Workflow 

Microsoft Windows

• Widely used on personal computers, business workstations, and servers.

• It provides a graphical user interface, hardware management, networking, security features, and tools for application execution and system administration.

Windows Kernel

manages CPU, memory, processes, devices, and other system resources.

File Explorer

manages files, folders, drives, and storage locations. 

Task Manager

displays and manages processes, performance, applications, users, and services. 

Device Manager

manages hardware devices and their drivers. 

Command Prompt

provides a command-line environment. 

PowerShell

provides a powerful command-line shell and scripting environment. 

Services

manages background system and application services. 

Settings/Control tools

provide configuration options for hardware, software, accounts, and networking. 

NTFS

The primary modern Windows file system and supports permissions, security features, large volumes, and other advanced capabilities. 

FAT32

An older file system still encountered on removable storage but has limitations such as a 4 GB maximum individual file size. 

exFAT

Commonly used for removable storage and supports large files. 

User Accounts

identify users and determine access rights. 

Processes

running programs and system tasks that consume resources. 

Services

background components that perform specific functions. 

Drivers

software that allows Windows to communicate with hardware. 

Updates

deliver security fixes, bug fixes, and feature improvements. 

Security

includes authentication, permissions, firewall features, malware protection, and encryption technologies.

Linux

• open-source operating-system family built around the Linux kernel.

• widely used in servers, cloud platforms, development environments, networking, supercomputing, and embedded systems.

Hardware

physical components such as CPU, memory, storage, and devices. 

Kernel

manages hardware, memory, processes, devices, networking, and system calls. 

System Libraries

provide common functions used by programs.

Shell

accepts and interprets commands. 

System Utilities

provide administration and file-management functions.

Applications

software used to perform user tasks.

/home

contains user home directories. 

/etc

contains system and application configuration files. 

/var

contains variable data such as logs and caches. 

/usr

contains many user applications and system resources