The telephone system model is organized as a highly redundant, multilevel hierarchy. It comprises of the following components −Telephone of the subscriber or end userEnd office − Local central office directly connected to end user at a distance of 1 – 10km.Local loop − A two-way connection between the telephone and the end office.Toll office − switching centres which are called tandem offices when located within the same local area.Toll connecting trunk − Lines that connect end offices with toll offices.Intermediate switching offices − Interconnected non-hierarchical switching offices for connecting toll offices.Inter toll trunk − Very high bandwidth channels that ... Read More

Public Switched Telephone Network (PSTN) is an agglomeration of an interconnected network of telephone lines owned by both governments as well as commercial organizations. Properties of PSTN It is also known as Plain Old Telephone Service (POTS) It has evolved from the invention of telephone by Alexander Graham Bell. The individual networks can be owned by national government, regional government or private telephone operators. Its main objective is to transmit human voice in a recognizable form. It is an aggregation of circuit-switched networks of the world. Originally, it was an entirely analog network laid with copper cables ... Read More

Frequency division multiplexing (FDM) is a technique of multiplexing, where the users are allowed the total available bandwidth on time sharing basis. Here the time domain is divided into several recurrent slots of fixed length, and each signal is allotted a time slot on a round-robin basis.Concept and ProcessIn TDM, the data flow of each input stream is divided into units. One unit may be 1 bit, 1 byte, or a block of few bytes. Each input unit is allotted an input time slot. One input unit corresponds to one output unit and is allotted an output time slot. During ... Read More

A computer system is basically a machine that simplifies complicated tasks. It should maximize performance and reduce costs as well as power consumption. The different components in the Computer System Architecture are Input Unit, Output Unit, Storage Unit, Arithmetic Logic Unit, Control Unit etc.A diagram that shows the flow of data between these units is as follows −The input data travels from input unit to ALU. Similarly, the computed data travels from ALU to output unit. The data constantly moves from storage unit to ALU and back again. This is because stored data is computed on before being stored again. ... Read More

Clustering 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. There are two types of Clustering systems i.e. asymmetric and symmetric clustering systems. Details about these are given as follows −Asymmetric Clustering SystemIn this system, one of the nodes in the clustered system is in hot standby mode and all the others run the required applications. The hot standby mode is a failsafe in which a hot standby node is part of the system . The hot standby ... 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.Clustered System StructureThe structure of a clustered system is given as follows −Some details about the above structure are −The clustered system contains tightly couples individual nodes. However, the degree of coupling in the system may vary. Some jobs may require constant communication between the nodes while there are also jobs that may only ... Read More

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