Computer Storage contains many computer components that are used to store data. It is traditionally divided into primary storage, secondary storage and tertiary storage. Details about these storage types and devices used in them are as follows −Primary StoragePrimary storage is also known as the main memory and is the memory directly accessible by the CPU. Some primary storage devices are −ROMROM is read only memory. This memory cannot be changed, it can only be read as required. Since ROM is unchangeable memory, it is used by data and programs that are frequently required and seldom changed, like the system ... Read More

Clustered systems are similar to parallel systems as they both have multiple CPUs. However a major difference is that clustered systems are created by two or more individual computer systems merged together. Basically, they have independent computer systems with a common storage and the systems work together.A diagram to better illustrate this is −The clustered systems are a combination of hardware clusters and software clusters. The hardware clusters help in sharing of high performance disks between the systems. The software clusters makes all the systems work together .Each node in the clustered systems contains the cluster software. This software monitors ... Read More

A bitmap is a mapping from one system such as integers to bits. It is also known as bitmap index or a bit array.The memory is divided into units for bitmap. These units may range from a few bytes to several kilobytes. Each memory unit is associated with a bit in the bitmap. If the unit is occupied, the bit is 1 and if it is empty, the bit is zero.The bitmap provides a relatively easy way to keep track of memory as the size of the bitmap is only dependent on the size of the memory and the size ... Read More

An operating system is a construct that allows the user application programs to interact with the system hardware. Operating system by itself does not provide any function but it provides an atmosphere in which different applications and programs can do useful work.The major operations of the operating system are process management, memory management, device management and file management. These are given in detail as follows:Process ManagementThe operating system is responsible for managing the processes i.e assigning the processor to a process at a time. This is known as process scheduling. The different algorithms used for process scheduling are FCFS (first ... Read More

I/O devices are very important in the computer systems.They provide users the means of interacting with the system. So there is a separate I/O system devoted to handling the I/O devices.The different Components of the I/O systems are −I/O HardwareThere are many I/O devices handled by the operating system such as mouse, keyboard, disk drive etc. There are different device drivers that can be connected to the operating system to handle a specific device. The device controller is an interface between the device and the device driver.A diagram to represent this is −I/O Application InterfaceThe user applications can access all ... Read More

Protection and security requires that computer resources such as CPU, softwares, memory etc. are protected. This extends to the operating system as well as the data in the system. This can be done by ensuring integrity, confidentiality and availability in the operating system. The system must be protect against unauthorized access, viruses, worms etc. Threats to Protection and Security A threat is a program that is malicious in nature and leads to harmful effects for the system. Some of the common threats that occur in a system are − Virus Viruses are generally small snippets of code embedded in a ... Read More

A computer system uses many devices, arranged in different ways to solve many problems. This constitutes a computing environment where many computers are used to process and exchange information to handle multiple issues.The different types of Computing Environments are −Let us begin with Personal Computing Environment −Personal Computing EnvironmentIn the personal computing environment, there is a single computer system. All the system processes are available on the computer and executed there. The different devices that constitute a personal computing environment are laptops, mobiles, printers, computer systems, scanners etc.Time Sharing Computing EnvironmentThe time sharing computing environment allows multiple users to share ... Read More

The kernel data structures are very important as they store data about the current state of the system. For example, if a new process is created in the system, a kernel data structure is created that contains the details about the process.Most of the kernel data structures are only accessible by the kernel and its subsystems. They may contain data as well as pointers to other data structures.Kernel ComponentsThe kernel stores and organizes a lot of information. So it has data about which processes are running in the system, their memory requirements, files in use etc. To handle all this, ... Read More

Virtualization in operating system changes a normal operating system so that it can run different types of applications that may be handled on a single computer system by many users. The operating system may appear different to each user and each of them may believe they are interacting with the only operating system i.e. this does not interfere with user experience.Operating system virtualization can also be used to migrate a process from one instance of the operating system to another. However, all the processes in the system are isolated and there operations are strictly monitored so there are no discrepancies ... Read More

Hashing is the process of generating a value from a text or a list of numbers using a mathematical function known as a hash function.There are many hash functions that use numeric numeric or alphanumeric keys. Different hash functions are given below:Hash FunctionsThe following are some of the Hash Functions −Division MethodThis is the easiest method to create a hash function. The hash function can be described as −h(k) = k mod nHere, h(k) is the hash value obtained by dividing the key value k by size of hash table n using the remainder. It is best that n is ... Read More