16.1 Purposes of an Operating System

An Operating System (OS) is a fundamental piece of software that manages computer hardware and software resources. Its primary purpose is to provide a platform for applications to run and to ensure efficient and effective utilization of the computer system. This section explores how an OS maximizes resource utilization.

Core Purposes of an Operating System

Operating systems serve several crucial purposes. These can be broadly categorized as:

• Resource Management: Controlling access to hardware and software resources.
• User Interface: Providing a way for users to interact with the computer.
• Process Management: Managing the execution of programs.
• Memory Management: Allocating and deallocating memory to processes.
• File Management: Organizing and managing files and directories.

Maximising Resource Use: How the OS Works

A key function of an OS is to optimise the use of available resources. This is achieved through various mechanisms:

1. CPU Scheduling

The CPU is a limited resource. The OS employs scheduling algorithms to determine which process gets to use the CPU and for how long. This prevents a single process from monopolizing the CPU and ensures fairness among competing processes.

Common CPU scheduling algorithms include:

• First-Come, First-Served (FCFS): Simple, but can lead to long waiting times for processes.
• Shortest Job First (SJF): Aims to minimise average waiting time.
• Priority Scheduling: Processes are assigned priorities, with higher priority processes getting preference.
• Round Robin: Each process gets a fixed time slice, promoting fairness.

2. Memory Management

The OS manages the computer's memory to ensure that processes have the memory they need to run, while preventing conflicts between processes. Techniques include:

• Virtual Memory: Allows processes to use more memory than is physically available by using disk space as an extension of RAM.
• Paging: Divides memory into fixed-size pages.
• Segmentation: Divides memory into logical segments.
• Memory Allocation Algorithms: Algorithms like First-Fit, Best-Fit, and Worst-Fit are used to allocate memory blocks to processes.

3. I/O Management

The OS manages input and output devices, ensuring efficient data transfer between the computer and peripherals. This involves:

• Device Drivers: Software that allows the OS to communicate with specific hardware devices.
• Interrupt Handling: The OS responds to signals from devices to handle I/O requests.
• Buffering: Temporarily storing data during I/O operations to improve efficiency.

4. Multitasking

The OS enables multitasking, allowing multiple processes to appear to run concurrently. This is achieved through time-sharing, where the CPU rapidly switches between processes, giving each process a small slice of time.

5. Resource Sharing

The OS facilitates sharing of resources like printers, files, and network connections among multiple processes. This reduces the overall cost and improves efficiency.

Technique	Description	Benefit to Resource Maximisation
CPU Scheduling (Round Robin)	Each process gets a time slice.	Prevents CPU monopolisation, ensuring fairness and better CPU utilisation.
Virtual Memory	Uses disk space as an extension of RAM.	Allows running larger programs than physical memory allows, improving overall system capacity.
Paging	Divides memory into fixed-size pages.	Efficient memory allocation and utilisation.
Multitasking	Allows multiple processes to run concurrently.	Maximises CPU utilisation by keeping the CPU busy.
Resource Sharing	Allows multiple processes to share resources.	Reduces the number of physical resources required and improves efficiency.

Conclusion

The operating system plays a vital role in maximising the use of computer resources. Through sophisticated scheduling, memory management, and I/O handling techniques, the OS ensures that the computer system operates efficiently and effectively, providing a smooth and productive computing experience.