Unit 1 Introduction to Operating System
Most Frequently Asked Question with Answer
Q1. Write down the different types of an operating system and also write function of an operating system?
Types of Operating Systems:
- Single-user operating systems: These are designed to be used by only one user at a time. Examples include Windows 10, macOS, and Linux distributions such as Ubuntu, Fedora, and Debian.
- Multi-user operating systems: These are designed to be used by multiple users simultaneously. Examples include Windows Server, UNIX, and Linux distributions such as CentOS and Red Hat Enterprise Linux.
- Real-time operating systems: These are designed for systems that require quick response times and predictable behavior. Examples include systems used in robotics, medical equipment, and aerospace.
- Network operating systems: These are designed to manage and control network resources. Examples include Novell Netware, Microsoft Windows Server, and Linux distributions such as Ubuntu Server and Red Hat Enterprise Linux.
Functions of Operating Systems:
- Resource management: The operating system manages the computer’s hardware resources, such as memory, CPU, input/output devices, and storage.
- Memory management: The operating system allocates and deallocates memory to running programs, ensuring that each program has the necessary memory to run correctly.
- Process management: The operating system manages the execution of multiple programs, ensuring that each program gets the necessary CPU time and other resources to run correctly.
- File management: The operating system manages the creation, deletion, and manipulation of files and directories, ensuring that data is stored and retrieved efficiently and securely.
- Security: The operating system provides security mechanisms to protect the system and user data from unauthorized access and other security threats.
- User interface: The operating system provides a user interface for users to interact with the computer and run applications.
- Device driver management: The operating system manages the communication between the computer hardware and software, ensuring that device drivers are loaded correctly and working correctly.
- Networking: The operating system provides networking functionality, allowing computers to communicate with each other and share resources.
Q2. Differentiate between the following
- Hard Real Time and Soft Real Time
- Multi Processing and Multi Programming
1. Hard Real Time vs Soft Real Time:
Hard Real Time Operating Systems are designed to meet strict timing constraints, where the system must respond to events within a guaranteed time frame. For example, real-time systems used in aerospace, medical equipment, or automotive applications require hard real-time operating systems. If the system misses the deadline, it can lead to catastrophic consequences.
On the other hand, Soft Real Time Operating Systems are designed to meet less strict timing constraints, where the system does not need to respond within a guaranteed time frame, but it should respond as quickly as possible. Examples include multimedia applications or online video conferencing, where a delay can cause inconvenience but not a catastrophic failure.
2. Multi Processing vs Multi Programming:
Multiprocessing is the use of multiple CPUs or cores in a single computer system, allowing multiple processes to run concurrently. In multiprocessing, multiple processes can be executed simultaneously, providing high performance and better resource utilization. Multiprocessing can be implemented in both hardware and software, and it requires a specialized operating system to manage the multiple CPUs.
On the other hand, Multiprogramming is the technique of running multiple programs concurrently on a single processor. In Multiprogramming, multiple programs can be stored in the main memory, and the CPU switches between them to give the illusion that they are running simultaneously. Multiprogramming improves the CPU utilization and reduces the waiting time for I/O operations.
In summary, multiprocessing involves multiple CPUs or cores, while multiprogramming involves multiple programs running on a single CPU. Multiprocessing improves performance by executing multiple processes simultaneously, while multiprogramming improves CPU utilization by allowing multiple programs to use the CPU concurrently.
Q3. Explain layered structure of operating system?
The layered structure of an operating system is a common architecture used to organize the various components and services of an operating system. It is also known as a hierarchical structure or a modular structure. In this architecture, the components of the operating system are organized into layers, where each layer provides a set of services to the layer above it and utilizes services provided by the layer below it.
The layered structure typically consists of four to five layers, with each layer representing a different level of abstraction. The exact number and type of layers can vary depending on the specific operating system and design. Here is a general overview of the layers:
- Hardware Layer: The bottom layer of the operating system is the hardware layer, which provides low-level access to the computer hardware, such as the CPU, memory, and I/O devices.
- Kernel Layer: The kernel layer sits on top of the hardware layer and provides basic operating system services, such as memory management, process scheduling, and device drivers. The kernel layer is the heart of the operating system and directly interacts with the hardware.
- System Call Layer: The system call layer sits on top of the kernel layer and provides an interface for user programs to access the services provided by the kernel. System calls are a set of functions that allow user programs to request services from the operating system.
- Utility Layer: The utility layer sits on top of the system call layer and provides high-level operating system services, such as file management, network services, and security services. The utility layer is typically implemented as a set of user-level programs that run on top of the operating system.
- User Layer: The user layer is the topmost layer of the operating system and consists of user applications that run on top of the utility layer. User applications are programs that are written to perform specific tasks, such as word processing, email, or web browsing.
The layered structure of an operating system provides a modular and organized way to develop and maintain the operating system. Each layer can be developed and tested independently, making it easier to add new features or fix bugs without affecting other layers. It also provides a clear separation of concerns between the hardware and the user applications, making it easier to understand and manage the system.
Q4.Define the services provided by the operating system?
Operating systems provide a range of services to applications and users to ensure efficient and secure use of computer hardware and resources.
The services provided by the operating system can be broadly categorized into the following categories:
- Process Management Services: The operating system provides services to manage processes or programs running on the computer. This includes creating and deleting processes, scheduling processes to run on the CPU, and managing process communication and synchronization.
- Memory Management Services: The operating system provides services to manage computer memory efficiently. This includes allocating and deallocating memory for processes, managing memory access permissions, and providing virtual memory support to enable programs to access more memory than physically available.
- File Management Services: The operating system provides services to manage files and directories stored on the computer. This includes creating, deleting, and renaming files and directories, managing file access permissions, and providing file input/output services to enable programs to read and write files.
- Device Management Services: The operating system provides services to manage computer devices such as input/output devices, storage devices, and networking devices. This includes managing device drivers, providing device input/output services to enable programs to communicate with devices, and managing device access permissions.
- Security Services: The operating system provides services to ensure the security of the computer and its resources. This includes providing user authentication and access control services, managing system-level security settings, and providing virus protection and other security services.
- Network Services: The operating system provides services to enable communication and data transfer between computers on a network. This includes providing networking protocols, managing network connections and devices, and providing network security services.
Overall, the operating system plays a critical role in managing computer resources and providing essential services to applications and users, ensuring the efficient and secure use of the computer.
Q5. Differentiate between the following’
- Shell and Kernel
- Monolithic Kernel and Micro Kernel
1. Shell and Kernel:
Shell is a user-level program that provides an interface for users to interact with the operating system. It accepts commands from users and executes them by making system calls to the kernel. In other words, the shell acts as an intermediary between the user and the operating system. The shell provides a command-line interface (CLI) or a graphical user interface (GUI) to interact with the operating system.
Kernel, on the other hand, is the core of the operating system that manages the hardware resources and provides services to user programs. It directly interacts with the hardware and provides low-level services such as process scheduling, memory management, device management, and security. The kernel is responsible for managing the system resources and ensuring that user programs have access to them.
2. Monolithic Kernel and Micro Kernel:
Monolithic Kernel is an operating system architecture where the entire operating system is implemented as a single executable file running in kernel mode. In a monolithic kernel, all operating system services, such as process management, memory management, device drivers, and file systems, are implemented in a single module that runs in kernel mode. The monolithic kernel architecture provides high performance since all system services are located in the same address space, making communication between them fast and efficient.
Micro Kernel, on the other hand, is an operating system architecture where the kernel is divided into small, independent modules, with only the essential services, such as process management and memory management, implemented in the kernel. Other services, such as device drivers, file systems, and network stacks, run as separate processes in user space. The microkernel architecture provides better security and reliability since a bug or crash in a user-level process does not affect other processes or the kernel. However, this architecture may result in a performance overhead due to the increased communication overhead between user-level processes.
In summary, the shell provides an interface for users to interact with the operating system, while the kernel manages the hardware resources and provides services to user programs. The monolithic kernel is an operating system architecture where all system services are implemented in a single module, while the microkernel architecture divides the kernel into small, independent modules, with only essential services implemented in the kernel.
Q6. How is a system call handled by the system? Enumerate the five system calls used in process management?
When a user program needs to perform a privileged operation, such as reading or writing to a file, allocating memory, or creating a new process, it must make a system call to request the operating system to perform that operation on its behalf. Here is a general overview of how a system call is handled by the system:
- User program makes a system call by invoking a special instruction, such as INT 0x80 on x86 processors or SVC on ARM processors.
- The CPU switches from user mode to kernel mode and transfers control to the interrupt handler or system call handler, which is a part of the operating system.
- The system call handler checks the parameters passed by the user program and verifies that they are valid and authorized.
- The system call handler performs the requested operation on behalf of the user program. For example, if the user program requested to read data from a file, the system call handler would read the data from the file and return it to the user program.
- The system call handler returns control to the user program, and the CPU switches back to user mode.
Here are five system calls commonly used in process management:
- fork(): This system call creates a new process by duplicating the calling process. The new process, called the child process, is an exact copy of the calling process, called the parent process, except for some values such as process ID and file descriptors.
- exec(): This system call replaces the current process image with a new process image. It loads a new program into the current process, replacing the previous program.
- wait(): This system call suspends the calling process until one of its child processes terminates. It allows the parent process to synchronize with its child processes.
- exit(): This system call terminates the calling process and frees all its resources, such as memory and file descriptors.
- kill(): This system call sends a signal to a specified process or a group of processes. Signals are used for inter process communication and can be used to terminate a process, interrupt a process, or handle various events.