Computer knowledge

Deadlock Questions and Answers pdf Define a deadlock? A process is said to be in a state of deadlock if it is waiting for a particular event (e.g. allocation of resources) that will never occur. Name four necessary conditions for Deadlock? Mutual Exclusion  Hold-and-Wait No Preempting  Circular Wait Describe the Mutual Exclusion condition for deadlock? Mutual exclusion condition indicates the locking of resources in exclusive mode, also known as a non-shareable mode. Each resource may be allocated to only one process at a time. If another process needs to use that resources, then the requesting process must wait until the resources have been released. What is the Hold-and Wait condition for deadlock? In a deadlock, each involved process holds one or more resources and waits for additional resources, which are currently being held by other processes in the system. It means that a deadlock may occur only if every involved process holds one or more resources and further needs add...

 Virtual Memory Exam Questions and Answers Define Virtual memory. What is its main advantage? Virtual memory is a logical technique that allows the execution of processes that are not completely in the main memory of a computer system. Only the main pages of a process are loaded into memory while the remaining pages are kept on the backing store. The main advantage of the virtual memory technique is that it allows users to execute processes that are larger than the actual size of physical memory. What do you know about demand paging? Demand paging is a logical technique, which is commonly used to implement virtual memory in a system. This logical technique has combined features of simple paging and overlaying in a system. In a demand-paged system, each page of a process is stored contiguously in the paging swap space on secondary storage (disk). With demand paging, a page is loaded into main memory only when it is needed (or demanded) during process execution. What is meant by page...

File Management Questions and Answers pdf  Define a File system? Files are managed by the operating system. The part of the operating system that deals with files are known as the file system. The major responsibilities of the file system are: How files are structured? How files are accessed and used? How files are protected? etc. What are File attributes? All operating systems associate the following information with each file, such as: Date and Time when the file was created or modified. Size of the file in bytes or KB or MB or higher memory units. Location of the file with the complete path on the storage media. Type of file. The Identifier, which identifies the file within a file system. The file name and the above-mentioned information about a file is known as attributes of the file. The attributes vary from one operating system to another. Describe the Direct Access Method? The direct access method is also known as the random access method. It is a very fast method to access ...

 CPU scheduling questions and answers pdf: What is CPU scheduling? The method or procedure to schedule the processes to execute on a CPU is known as CPU scheduling or process scheduling. What is the difference between preemptive and Non-preemptive scheduling in a system? In non-preemptive scheduling, once the CPU is allocated to a process, the process holds (retains) the CPU until it switches from running state to waiting for the state, or running state to ready state, or waiting for the state to a ready state, or it terminates. In preemptive scheduling, a process may be released from the CPU by the operating system. The scheduler may suspend the execution of a process before it is blocked or terminated, to allocate the CPU to another process. What is a dispatcher? In multiprogramming and multitasking environments, switching of processes occurs so frequently that the operating system needs a special program (or module) to accomplish this task. This program is known as dispatcher. T...

 Computer Organization Quiz Questions With Answers Answer the following question briefly: What is the main function of an I/O Module?  For this purpose, the computer uses an Input /Output System or I/O system. This I/O system consists of two parts:(i) I/O device and (ii) I/O module. I/O device is also called a peripheral device, whereas I/O module is also known as I/O controller or controller device or simple controller. The data or program instructions are moved between the computer and its peripheral devices through the I/O module. What does the CPU do when there is no program to run in a system network? The CPU remains busy to do something as long as the computer is turned on. When there is no user program to run, the operating system will execute a loop that does nothing until an interrupt (break to normal executed) occurs. This loop is called the busy-wait loop or idle loop. Write down the function of MAR in a computer system? This register holds the address of memory whe...

What are Linux Basic Commands? LINUX COMMAND Some important Linux commands are as follows: The PWD Command: ''pwd'' stands for present working directory. This command shows the required name and location of the current directory in a list, which is the directory (also called a folder on some operating systems) in which the user is currently working a system. PWD [press Enter] The Is Command: The Is command displays the names of the files and directories in the current working directory. Several options are available for displaying details about the file. Basic Command for the Linux vi Editor: The vi started b y simply entering ''vi''(it is case sensitive) at the Linux prompt, and once started is excited using ESC:q! to abandon changes or SHIFT+ZZ (case sensitive) to save changes. If you want to edit (or create) a specific file uses the command ''vi/path-to-file/name-of-file''. The ''path-to-file'' must already exist as vi ...

Virtual File System in OS VIRTUAL FILE SYSTEM: A virtual file system (VPS) or virtual system switch is an abstraction layer on top of a more concrete file system of computer technology to handle every system clearly also in a kernel operating system. The purpose of a VPS is to allow client applications in a files management system to access different types of concrete file systems uniformly.  for example:  A VPS can be used to access local and network storage devices that are CD-ROM, Disk Drive, etc transparently without the client application noticing the difference. The Linux kernel of the operating system implements the concept of Virtual System (VPS, originally virtual Filesystem Switch) so that it is possible to separate actual ''low-level'' file system code from the rest of the kernel operating system in the computer management system. The operating system kernel file system (VFS) is an interesting aspect of the Linux kernel because it provides a common interface ...

How to Prevent Computer Security Threats THREAT TO SECURITY:   A threat is defined as a computer program, a person, an accident, or events that violate (or break) the security system. A threat causes loss of data and attacks data privacy. The realization or understanding of a threat is known as an attack.  Threats may be categorized by the type of activity or by the type of the attacker. Three are four general categories of attacks: Interruption: This type of attack does not allow authorized users to access the system. This type of attack is also known as a denial of service attack. In this type of attack, some components of a system are destroyed or become unavailable. For example, a hard disk may be destroyed, or a communication line is cut off, etc. Interception: In this type of attack, unauthorized persons or programs can access computer resources (such as important information stored on I computer) The attacker can illegally copy some important data programs. The data can...

security management in an operating system Components of Security: All of the latest operating systems have to provide the security mechanism to protect the resources against potential security threats. The major components of security are as follows: User Authentication Prevention  Detected Identification  Correction  Password Vulnerability: Vulnerability means weakness or drawback. Although password protection is easy to implement it has problems too. It does not provide complete security. The major problems are as follows: It can be stored through a guess or secret observation There are two ways to guess a password. An Intruder: It may be a human or a program, which tries to guess the password of a specific user by entering information about the user such as names of his children, wife, departments, friends, his favorite hobbies or fruits, birds, animal,s, etc. Brute Force: Using this way, the password is guessed by trying all combinations of valid password characters,...

Importance of Operating System Security  Introduction of Security: In the modern age of computer networking, security has become a very important issue. The operating system must have well-designed mechanisms for protecting computer resources against potential threats like data theft, virus programs, accidental or intentional data loss, and unauthorized access. The computing resources include information stored in the system as well as memory, CPU, disks, devices, etc. Most of the information stored inside the computer system is highly valuable. Similarly, a process must be protected from improper interference by other processes. The protection mechanisms are implemented through protection policies. The protection policies may be built into the operating system or determined by the system administrator.  For example: a protection policy may determine which processes are authorized to abort another process. The protection policy may determine which processes are authorized to a...