# Types of Operating System ## What is an operating system? - An operating system is fundamental software that manages computer hardware, provides common services for programs, and acts as an interface between users and the machine - Several different types of operating systems exist, each with unique characteristics and purposes - Understanding these types is essential for both developing and using computer systems effectively

An operating system (OS) manages hardware resources, provides services to applications, and enables user interaction with the computer

## Categories of operating systems There are five main types of operating systems, each designed for different use cases and environments: | Type | Description | |------|-------------| | **Distributed Operating Systems** | Run on multiple machines appearing as a single unit, used for efficient task distribution and load balancing | | **Embedded Operating Systems** | Designed for specific tasks, is the system running inside a device that is not primarily a computer system, e.g. smart thermostat, coffee maker, robot vacuum | | **Multi-tasking Operating Systems** | Allows multiple tasks to run concurrently on a single processor, manages system resources and allocates CPU time to different processes | | **Multi-user Operating Systems** | Supports multiple users accessing computer resources concurrently, efficiently manages resource allocation, and provides features for data security and user privacy | | **Real-Time Operating Systems (RTOS)** | Designed for immediate data processing, can ensure tasks are processed in specific timeframes, highly efficient | ## Distributed operating systems - Operate across multiple connected machines that function as a unified system - Tasks are distributed across different nodes in the network for efficient processing - Enable load balancing by spreading workload across available machines - Provide resilience - if one machine fails, others can continue processing **Example**: Apache Hadoop is an open-source distributed OS designed to process massive datasets using multiple nodes in a distributed network. Companies like Netflix use distributed systems to handle millions of simultaneous streaming requests. ## Embedded operating systems - Run inside everyday devices that aren't primarily computers - Typically have a simple, focused set of functions they perform efficiently - Often use proprietary software tailored to the specific device - Generally more limited in capabilities compared to general-purpose operating systems

Most household appliances with digital controls contain embedded systems: smart thermostats, coffee makers, robot vacuums, and digital watches

**Examples**: - IoT (Internet of Things) devices contain embedded OS with specialized functions - A smart refrigerator runs an embedded system to monitor temperature, track inventory, and connect to mobile apps - These devices don't typically run well-known operating systems like Windows or macOS ## Multi-tasking operating systems - Enable multiple applications to run simultaneously on a single processor - The OS rapidly switches between tasks, creating the illusion of parallel execution - Manages system resources to ensure smooth operation across all running programs - Most modern desktop and laptop operating systems support multi-tasking **Examples**: Windows, macOS, and Linux are multi-tasking OS that allow users to browse the web, edit documents, stream music, and run antivirus scans simultaneously.

When you have a browser, word processor, and music player open at once, the multi-tasking OS is rapidly switching CPU time between them

## Multi-user operating systems - Allow multiple users to access the same computer resources at the same time - Each user has their own account with separate files and settings - Efficiently manages resource allocation between different users - Provides security features to protect each user's data from others - Implements permissions systems to control what each user can access **Examples**: - Windows, macOS, and Linux are multi-user OSs where different family members can have separate accounts on the same computer - University computer labs use multi-user systems where dozens of students can log into different workstations

Multi-user systems require robust security to prevent users from accessing or modifying other users' data

## Real-time operating systems (RTOS) - Process data with minimal delay - responses occur within strict time constraints - Guarantee tasks complete within specified timeframes (deterministic behavior) - Prioritize time-critical operations over throughput - Essential in situations where delayed responses could be dangerous or costly **Applications where RTOS is critical**: - **Aerospace**: Flight control systems must respond instantly to sensor data - **Automotive**: Anti-lock braking systems (ABS) require immediate reaction to wheel sensors - **Medical devices**: Pacemakers must deliver electrical impulses at precise intervals - **Industrial robotics**: Assembly line robots need precise timing for coordination

In safety-critical systems like aircraft or medical devices, even millisecond delays in processing can have catastrophic consequences

**Example**: An autonomous vehicle uses an RTOS to process data from cameras, radar, and lidar sensors in real-time. If the system detects a pedestrian stepping into the road, it must react within milliseconds to brake safely. ## Comparison table | Type | Example Use Case | Key Benefit | Key Limitation | |------|------------------|-------------|----------------| | **Distributed** | Cloud computing platforms processing big data | Spreads workload across many machines | Complex to configure and maintain | | **Embedded** | Smart home devices | Efficient for specific, limited tasks | Cannot run general-purpose software | | **Multi-tasking** | Personal laptops and desktops | Run many programs at once | Performance degrades if too many processes active | | **Multi-user** | School or office computer networks | Multiple people share same hardware | Requires user authentication and permissions | | **Real-Time** | Industrial control systems | Guaranteed response times | Expensive and complex to develop | ## Worked example 1: Self-driving vehicles **Question**: A taxi firm is investigating replacing its drivers with self-driving cars. Explain why the self-driving system will use a real-time operating system. [3] ### How to answer: - State the purpose and advantages of a real-time operating system - Link the advantages to the specific scenario in the question - Consider safety implications of delayed processing ### Answer: A self-driving car system must process data in real-time from input sensors such as cameras and radar. Data needs to be processed instantly so that the vehicle can operate safely. A vehicle that cannot process data quickly will be an unreliable danger to people. Faster processing of input data will lead to safer operation of the vehicle. A real-time system will replicate hazard perception, navigation, and vehicle control that humans can instinctively do. **Acceptable shorter answer**: An operating system needs to process tasks quickly. A real-time operating system needs to process them instantly. A real-time operating system should be used in a self-driving car so that it can react to hazards quickly. ## Worked example 2: Virtual assistant device **Question**: A company releases an in-home virtual assistant called 'Smart Home Hub'. When placed in a room, the device listens out for the phrase "Hey Hub". When someone says that phrase, it listens to the following question and tries to give a relevant answer. The Smart Home Hub device runs off an embedded operating system. Define the term 'embedded operating system'. [2] ### How to answer: - Recall the features of an embedded system - Use the scenario to include examples in your answer ### Answer: Embedded systems are those running inside everyday items that are not primarily computers. Embedded systems usually have a simple set of features that they perform efficiently. Some other embedded systems, such as smart thermostats, have much simpler features and functions. **Acceptable shorter answer**: An embedded system runs in most household devices that require some processing, e.g. smart thermostats, coffee makers, digital alarm clocks. ## Worked example 3: Medical monitoring system **Question**: A hospital uses a patient monitoring system that continuously tracks heart rate, blood pressure, and oxygen levels. Medical staff need to be alerted immediately if any reading becomes dangerous. Explain why this system would use a real-time operating system rather than a multi-tasking operating system. [3] ### How to answer: - Identify the critical timing requirements of the medical scenario - Explain how RTOS guarantees timely responses - Contrast with limitations of multi-tasking systems ### Answer: A real-time operating system is essential for the patient monitoring system because it guarantees that critical alerts are processed within strict time constraints. If a patient's heart rate drops dangerously low, the system must alert medical staff within milliseconds. A multi-tasking operating system might delay this alert if the CPU is busy with other processes, potentially putting the patient's life at risk. RTOS prioritizes time-critical medical alerts over less urgent tasks, ensuring reliable and predictable response times in life-or-death situations. **Acceptable shorter answer**: Real-time operating systems process urgent tasks immediately within guaranteed timeframes. In patient monitoring, delays of even seconds could be fatal. Multi-tasking systems might delay alerts while handling other processes, making them unsuitable for this critical medical application.