The evolution and scope of OSs

OSs can be classified along two major dimensions.

1. The evolution of OSs over time, as driven by advances in new hardware technologies.
2. OSs into classes based on the main application environments.

The Five Generations of Computer Systems

Operating systems have evolved across five major generations, each driven by new hardware technologies.

1. First Generation: Vacuum Tubes

• Enabling Hardware: Vacuum tubes
• OS Type: None
• Defining Characteristics: Early computers did not have an operating system. Programmers had to work directly in machine language to create programs without any OS support. This meant only experts could program these machines, and operations were very limited.

2. Second Generation: Transistors

• Enabling Hardware: Transistors, replacing vacuum tubes
• OS Type: Batch OS
• Defining Characteristics: Transistors made computers faster and smaller. The operating system in this generation handled batches of jobs, automating the compilation, loading, and execution of programs. Multiprogramming allowed the OS to execute multiple jobs more efficiently by scheduling CPU time and resources.

3. Third Generation: Integrated Circuits (IC)

• Enabling Hardware: Integrated circuits (ICs) replaced individual transistors
• OS Type: Interactive multi-user OS
• Defining Characteristics: This generation saw the introduction of time-sharing systems, which allowed multiple users to interact with the computer simultaneously through terminals. The OS managed interruptions and helped manage more memory and secondary storage resources.

4. Fourth Generation: Very Large Scale Integration (VLSI)

• Enabling Hardware: VLSI, which enabled the creation of microprocessors and personal computers (PCs)
• OS Type: Desktop and laptop OS
• Defining Characteristics: Personal computers became widespread, and the OS handled everything from booting to multitasking. User-friendliness became a priority, with the introduction of Graphical User Interfaces (GUIs) allowing easier interaction with machines.

5. Fifth Generation: Networking Hardware

• Enabling Hardware: Networking hardware
• OS Type: OSs for supercomputers, distributed systems, and mobile devices
• Defining Characteristics: This generation was marked by powerful chips, supercomputers, and the rise of the internet. OSs now managed parallel processing, networking, and security. Wireless communication and mobile devices created additional requirements for OS capabilities.

Classification Based on Application Environments

1. Mainframe Systems: Used in large organizations for high-volume data processing and management.
2. Server Systems: Designed to provide services to multiple clients, such as web and email processing.
3. Desktop and Laptop Systems: Intended for personal use, offering a user-friendly interface for various tasks.
4. Embedded Systems: Found in devices like smartphones, tablets, and IoT devices, often with limited resources and specialized functions.
5. Real-Time Systems: Used in applications requiring immediate responses, such as industrial control and medical equipment.