History and Overview of DOS

Brief History of DOS

• MS-DOS was introduced by Microsoft for IBM PCs in 1981 becoming the most widely used OS in the early 1980s
• IBM released PC-DOS in 1982, which was a customized version of MS-DOS for IBM PCs
• DOS continued to evolve with several versions from 1983-1990, each with added features and capabilities
• DOS started to decline with the introduction of Windows 95 but remained important for bootstrapping Windows and running certain applications

Overview of DOS

• DOS is a text-based OS relying on command-line input through commands
• MS-DOS was developed by Microsoft for IBM PCs
• PC-DOS which was essentially the same but customized for IBM hardware
• DOS is a single-tasking OS, meaning it can run only one application at a time

Key Features of DOS

• File Management: Commands can create, delete, copy, and manage files and directories on a disk
• Batch Files: Users can create .BAT files to automate command sequences
• Memory Management: Uses conventional memory (first 640KB) and can access extended and expanded memory with specific drivers
• Device Drivers: Requires drivers to interact with hardware devices

Basic DOS Commands

• DIR: Lists files and directories in the current directory
• COPY: Copies files from one location to another
• DEL: Deletes files
• CD: Changes the current directory
• FORMAT: Prepares a disk for use by erasing all data on it

Historical Significance of DOS

• DOS laid the groundwork for many modern OS concepts and features
• DOS started to decline with the advent of Windows 95 as Windows' GUI became more popular

Comparison: DOS vs. Modern OS - User Interface

• DOS: Uses command-line interface (CLI), requiring users to type commands
• Modern OS: Uses a graphical user interface (GUI), which allows users to interact with visual elements

Comparison: DOS vs. Modern OS - Multitasking

• DOS: Single-tasking, meaning it can execute just one task or program at a time
• Modern OS: Multitasking, which allows multiple applications to run simultaneously

Comparison: DOS vs. Modern OS - Memory Management

• DOS: Limited to managing conventional memory (first 640KB) and needs specific configurations for extended or expanded memory
• Modern OS: Advanced memory management, handling large amounts of RAM and virtual memory

Comparison: DOS vs. Modern OS - Device Drivers

• DOS: Requires manual installation and configuration of device drivers
• Modern OS: Automatically detects and installs drivers for most hardware

Comparison: DOS vs. Modern OS - File System

• DOS: USES the FAT (File Allocation Table) file system, which has limitations in file size and disk partition size
• Modern OS: Supports advanced file systems, offering better security, reliability, and performance

Comparison: DOS vs. Modern OS - Networking

• DOS: Has limited networking capabilities, often requiring third-party software and complicated setups
• Modern OS: Built-in networking support

Comparison: DOS vs. Modern OS - Security

• DOS: Basic security features, with limited user authentication and protection against malware
• Modern OS: Comprehensive security measures

Comparison: DOS vs. Modern OS - Software Support

• DOS: Limited software support is available, primarily for older, text-based applications
• Modern OS: Offers extensive software ecosystems

Comparison: DOS vs. Modern OS - User Experience

• DOS: Steeper learning curve due to the command-line interface
• Modern OS: Intuitive and user-friendly

Memory Management in DOS

• Conventional Memory: DOS operates in real mode, accessing only the first 640KB of memory
• Extended Memory (XMS): DOS can access memory beyond 1MB using Extended Memory Specification (XMS) and specific drivers
• Expanded Memory (EMS): Uses Expanded Memory Specification (EMS), an older method, plus DOS applications supporting EMS access additional memory

Memory Management in Modern Operating Systems

• Virtual Memory: Modern OS uses virtual memory, system uses hard disk space as RAM, increasing memory
• Protected Mode: Provides access to the full address space of the CPU and allows for advanced memory management techniques
• Memory Protection: Modern OS ensures memory protection, preventing one process from accessing another's memory space
• Multitasking and Process Management: Modern OS supports pre-emptive multitasking, OS manages memory allocations and deallocations for each process

Advanced Memory Allocation Techniques

• Modern OS uses demand paging and memory-mapped files for resource utilization

Function of DOS - File Management

• Allows creating, reading, writing, and deleting files and directories

Function of DOS - Memory Management

• Manages 640KB of conventional memory, accesses memory beyond 1MB using drivers

Function of DOS - Device Management

• Facilitates communication between the computer and hardware devices, supports peripheral devices

Function of DOS - Command Execution

• Provides a command-line interface (CLI), users can create batch files (.BAT) to automate tasks

Function of DOS - Program Execution

• Executes programs written for the DOS environment, single-tasking system

Function of DOS - System Configuration

• Uses configuration files to set system parameters and optimize performance, Bootstrapping Other Operating Systems

BOOT Process - Power-On Self-Test (POST)

• CPU starts executing the BIOS/UEFI firmware
• BIOS/UEFI tests RAM, hard drives and peripherals
• BIOS/UEFI will display error messages or beep codes if any issues are detected

BOOT Process - Boot Loader

• BIOS/UEFI checks the boot order settings to determine which device to boot from
• BIOS/UEFI reads MBR or GPT from the selected boot device
• BIOS/UEFI loads the boot loader into memory

BOOT Process - Operating System Initialization

• The boot loader locates and loads the OS kernel into memory
• The kernel initializes the system's hardware and sets up memory management

BOOT Process - System Startup

• The OS executes startup scripts and configuration files
• The OS presents a login screen (if required)
• The OS loads the GUI or CLI

BOOT Process - Ready for Use

• The computer is fully booted and ready for use

POST Process - Initiation

• CPU activated, executing BIOS/UEFI firmware

POST Process - Hardware Checks

• Memory Test: Checks RAM
• CPU Check: Verifies CPU
• Peripheral Devices: Checks keyboard, mouse etc
• Storage Devices: Checks hard drives and SSDs
• Graphics Card: Tests GPU

POST Process - Error Handling

• Beep Codes: Indicate specific hardware errors
• Error Messages: Display details about detected issues

POST Process - Initialization of Hardware

• BIOS/UEFI initializes peripherals, applies configuration settings

POST Process - Boot Device Selection

• BIOS/UEFI checks boot order settings, loads boot loader

POST Process - Transition to Boot Loader

• BIOS/UEFI hands over control to boot loader

Hardware Management

• OS manages the computer's hardware resources
• OS uses device drivers to communicate with hardware

Software Execution

• OS provides an environment for running software, modern OSs support multitasking

User Interface

• OS provides GUI and command-line interface (CLI)

File System Management

• OS manages the storage of files and directories, enforces file permissions

Security and Protection

• OS requires user login, includes security features

Memory Management

• OS manages memory, uses virtual memory

Networking

• OS provides networking capabilities and network management

System Stability and Error Handling

• OS offers crash recovery, resource monitoring

Operating System Selection Criteria

• Hardware and software compatibility
• Ease of use and customization options
• System and multitasking performance
• Security features and vulnerability management
• Official and community support and Licensing and ownership costs
• Receive updates and ease of maintenance and environment use

Windows Usability

• Windows has a user-friendly GUI compatibility making it popular for personal and business use
• Ideal For: Everyone
• Features: Support

macOS Usability

• macOS has design, interface, stability, user experience
• Ideal For: Professionals
• Features: Power and security

Linux Usability

• Linux is customizable with distributions, appealing to experienced users
• Ideal For: Experts
• Features: Community and support

Android Usability

• Android Is used for flexibility, customizability and extensive app ecosystem
• Ideal For: General Use
• Features: Support for Google Services

iOS Usability

• iOS design is for simplicity, performance, and security, seamless for consistent user experience.
• Ideal For: Users with a specific seamless and consistent user experience.
• Features: Access to their devices

Chrome OS Usability

• Chrome is lightweight for web and cloud
• Ideal For: Easy Web Based application
• Features: Google Integrations

Unix Usability

• Unix is a powerful, multi-user OS for stability and support
• Ideal For: Users with servers
• Features: security and networking features

Solaris Usability

• Solaris is scalable Known for Performance and security In enterprise
• Ideal For: Large Enterprises
• Features: Performance

Proprietary Operating Systems

• Definition: Developed and distributed by a single entity with exclusive control
• Cost: Purchases licenses or subscriptions
• Support: Official support, updates, and security patches
• Customization: Limited

Open-Source Operating Systems

• Definition: Distributed with the source code available to the public for modification and distribution
• Cost: Generally free
• Support: Rely on Community support
• Customization: Highly customizable

Choosing an OS Considerations for a Business

• Small Businesses (Retail, hospitality, small offices, freelancers)
• Medium-Sized Businesses (Professional services, manufacturing, healthcare, education)
• Large Enterprises (Finance, technology, telecommunications, large-scale manufacturing)
• Specialized Businesses (Data centers, research labs, development firms)