Unit 2: Types of Operating Systems

Operating Systems (OS) are the backbone of computer systems. Depending on the environment and system requirements, different types of operating systems have evolved. In this post, we’ll explore various OS types such as batch-processing, multiprogramming, multitasking, multiprocessing, distributed, and real-time operating systems.

This is Day 2 of our OS blog series.

1. Single Process Operating System

A Single Process OS can execute only one process at a time from the ready queue. It's one of the oldest and simplest types of OS.

Key Point: Only one job runs at any given time.

Example: MS-DOS

2. Batch-Processing Operating System

This type of OS was common in the early days of computing when user interaction with the processor was minimal.

Example: ATLAS, Manchester Univ, Late 1950s, early 1960s

How it works:

1. Users prepare jobs (e.g., using punch cards).

2. Jobs are submitted to a computer operator.

3. The operator collects and groups jobs into batches based on similar requirements.

4. Each batch is submitted to the processor one at a time.

5. All jobs in a batch are executed together.

Drawbacks:

• No job prioritization (urgent jobs may have to wait).

• Possibility of starvation for certain jobs.

• CPU can be idle during I/O operations.

3. Multiprogramming Operating System

Multiprogramming increases CPU utilization by keeping multiple jobs in memory at once.

Only one job is executed at a time, but others are ready in memory.

Example: THE, Dijikstra, early 1960s

Key Features:

• Uses context switching.

• Switches when a process goes to a wait state (e.g., I/O).

• Reduces CPU idle time.

4. Multitasking Operating System

Multitasking is an extension of multiprogramming that improves responsiveness by allowing multiple tasks to run seemingly at the same time.

Used in desktops, laptops, and personal computers.

Example: CTSS, MIT

Key Characteristics:

• Single CPU.

• Multiple tasks can run simultaneously (via time-sharing).

• Increases system responsiveness.

• Efficient context switching between tasks.

5. Multiprocessing Operating System

This OS supports systems with multiple CPUs.

Example: Windows-NT

Advantages:

• Parallel processing: jobs can be split across CPUs.

• Higher reliability – if one CPU fails, others continue.

• Improved throughput and reduced process starvation.

6. Distributed Operating System

A Distributed OS manages a group of independent computers and presents them as a single system to the user.

Example: LOCUS

Key Features:

• Loosely connected, autonomous systems.

• Shared resources across networked nodes (CPUs, memory, storage).

• Systems work together but may be physically separate.

• Ideal for large-scale resource sharing and load distribution.

7. Real-Time Operating System (RTOS)

RTOS is designed for systems where timing is critical.

Example: ATCS

Characteristics:

• Provides predictable and timely response to events.

• Prioritizes completing tasks within strict time boundaries.

• Used in:

  • Air traffic control systems

  • Industrial automation

  • Medical devices

  • Robotics

Summary