Functions of Operating Systems

An Operating System acts as a communication interface between the user and computer hardware. Its purpose is to provide a platform on which a user can execute programs conveniently and efficiently. The main goal of an operating system is to make the computer environment more convenient to use and to utilize resources most efficiently.

Operating System handles the following responsibilities:

• Controls all the computer resources.

• Provides valuable services to user programs.

• Coordinates the execution of user programs.

• Provides resources for user programs.

• Provides an interface (virtual machine) to the user.

• Hides the complexity of software.

• Supports multiple execution modes.

• Monitors the execution of user programs to prevent errors.

1. Process Management

Process management in operating system is about managing processes. A Process is a running program. The life cycle of process is from the moment program start until it finishes. Operating system makes sure each process:

• gets its turn to use the CPU

• synchronized when needed

• has access to the resources it needs, like memory, files, and input/output devices.

It also handles issues like process coordination and communication, while preventing conflicts such as deadlocks. This way, the OS ensures smooth multitasking and efficient resource use.

Core Functions in Process Management:

A. Process Scheduling

• Allocates CPU time to processes based on scheduling algorithms like Round Robin or Priority Scheduling.

• Ensures fair distribution of CPU time, avoiding starvation of lower-priority processes.

• Maximizes CPU utilization by determining which process runs at any given time.

B. Process Synchronization

• Coordinate multiple processes to ensure orderly execution and prevent conflicts.

• Prevents race conditions by ensuring that only one process can access a shared resource at a time.

• Uses synchronization mechanisms like locks, semaphores, and monitors to coordinate process access.

C. Deadlock Handling

• Prevents deadlocks by using strategies like resource allocation graphs or avoiding circular wait conditions.

• Detects deadlocks when they occur, allowing the system to identify and resolve the issue.

• Recovers from deadlocks by aborting or rolling back processes to free up resources.

D. Inter-Process Communication (IPC)

• Facilitates communication between processes through shared memory, allowing processes to exchange data directly.

• Uses message passing to send data between processes in different address spaces.

• Enables efficient data exchange and coordination in a multitasking environment, improving system performance.

2. Memory Management

Memory management is an essential task of the operating system that handles the storage and organization of data in both main (primary) memory and secondary storage. The OS ensures that memory is allocated and deallocated properly to keep programs running smoothly. It also manages the interaction between volatile main memory and non-volatile secondary storage.

Key Activities in Memory Management:

A. Main Memory Management

• Memory Allocation: Assigns memory to processes using techniques like paging and segmentation.

• Memory Deallocation: Frees memory when no longer needed.

• Memory Protection: Prevents processes from accessing each other’s memory.

• Virtual Memory: Uses disk space as extra memory to run larger processes.

• Fragmentation: Manages wasted memory space (internal/external) through compaction.

B. Secondary Memory Management

• Disk Space Allocation: Organizes how files are stored on the disk (contiguous, linked, indexed).

• File System Management: Manages files and directories for efficient data access.

• Free Space Management: Tracks available space on the disk.

• Disk Scheduling: Organizes the order of disk read/write requests.

• Backup and Recovery: Ensures data is backed up and can be restored after failure.

3. File System Management

File management in the operating system ensures the organized storage, access and control of files. The OS abstracts the physical storage details to present a logical view of files, making it easier for users to work with data. It manages how files are stored on different types of storage devices (like hard drives or SSDs) and ensures smooth access through directories and permissions.

File System Management includes managing of:

A. File Attributes

• File Name: Identifies the file with a name and extension (e.g., .txt, .jpg).

• File Type: Defines the format of the file (e.g., text, image, executable).

• Size: The amount of storage the file occupies.

• Permissions: Determines who can read, write, or execute the file.

B. File Types

• Text Files: Contain human-readable content (e.g., .txt, .md).

• Binary Files: Store data in binary format (e.g., .jpg, .mp3).

• Executable Files: Contain program code (e.g., .exe, .out).

C. Operations on Files

• Create: Allows users to create new files.

• Read: Opens files to read their contents.

• Write: Modifies the contents of a file.

• Delete: Removes a file from the system.

D. Access Methods

• Sequential Access: Reads data in order, from start to finish.

• Direct Access: Jumps to a specific part of the file.

• Indexed Access: Uses an index for quick data retrieval.

4. Device Management (I/O System)

Device management of an operating system handles the communication between the system and its hardware devices, like printers, disks or network interfaces. The OS provides device drivers to control these devices, using techniques like Direct Memory Access (DMA) for efficient data transfer and strategies like buffering and spooling to ensure smooth operation.

Major components in Device Management:

A. Device Drivers

The operating system uses device drivers to interact with hardware devices. There are two types of device drivers:

• Kernel-space drivers run in the OS kernel, offering direct access to hardware.

• User-space drivers run outside the kernel and are more isolated, providing safety but less performance.

B. Buffering & Caching

• Buffering temporarily stores data in memory to manage differences in device speeds. Block devices (e.g., hard drives) use larger blocks of data for buffering, while character devices (e.g., keyboards, mice) use smaller, byte-by-byte buffering.

• Caching improves access speed by storing frequently accessed data in a faster storage medium (like RAM).

C. Spooling 

Spooling manages data waiting to be processed, particularly in devices like printers. The OS places print jobs in a spool (a temporary storage area), allowing the CPU to continue other tasks while the printer works through the queue. Other examples include mail spooling (for managing outgoing email) and batch-job spooling (for managing scheduled tasks).

5. Protection and Security

Protection and security mechanisms in an operating system are designed to safeguard system resources from unauthorized access or misuse. These mechanisms control which processes or users can access specific resources (such as memory, files, and CPU time) and ensure that only authorized users can perform specific actions. While protection ensures proper access control, security focuses on defending the system against external and internal attacks.

A. Access Control

The operating system ensures that processes and users can only access resources they are authorized to. This is achieved through mechanisms like memory-addressing hardware (which keeps processes within their own address space) and timer interrupts (which prevent processes from monopolizing the CPU).

B. User Authentication

A system identifies users through user IDs (UIDs) or Security IDs (SIDs). During login, the operating system verifies the user’s credentials, ensuring that only authorized users can access their data or system resources.

C. Resource Protection

Mechanisms like file protection (ensuring only authorized users can access or modify files) and device protection (restricting direct access to device-control registers) ensure the integrity of system resources, preventing unauthorized or harmful use.

D. Security Against Attacks

Security mechanisms defend against external threats like viruses, worms, denial-of-service attacks, and identity theft. These attacks can misuse system resources, steal sensitive data, or disrupt system operation. The OS works to prevent these threats and minimize damage.

6. Additional Functions of the Operating System

Beyond core tasks like process and memory management, operating systems also focus on system performance, resource utilization and error detection. These functions ensure smooth operation, efficient resource allocation and system reliability.

A. Control Over System Performance

The OS monitors system performance by recording delays between service requests and system responses. This helps identify bottlenecks and optimize resource usage, ensuring efficient system operation.

B. Job Accounting

The OS keeps track of time and resources used by various tasks and users. This information is valuable for auditing, billing, and optimizing resource allocation among users and applications.

C. Error-Detecting Aids

The OS produces dumps, traces, error messages, and other debugging aids to detect and diagnose errors. This proactive approach helps maintain system stability and aids in troubleshooting issues.