An Application Programming Interface (API) contains software building tools, subroutine definitions as well as communication protocols that facilitate interaction between systems. An API may be for a database system, operating system, computer hardware or a web-based system.An Application Programming Interface makes it simpler to use certain technologies to build applications for the programmers. API can include specifications for data structures, variables, routines, object classes, remote calls etc.A diagram that shows the API in the system is as follows −Uses of Application Programming InterfacesAPI’s are useful in many scenarios. Some of these are given in detail as follows −Operating SystemsThe interface ... Read More

GUI is an interface that allows users to interact with different electronic devices using icons and other visual indicators. The graphical user interfaces were created because command line interfaces were quite complicated and it was difficult to learn all the commands in it.In today’s times, graphical user interfaces are used in many devices such as mobiles, MP3 players, gaming devices, smartphones etc.The below diagram provides the position of the graphical user interface with respect to the computer system −Elements in Graphical User InterfaceGraphical User Interface makes use of visual elements mostly. These elements define the appearance of the GUI. Some ... Read More

Modem is an abbreviation of “modulator demodulator”. It is a network device that modulates digital information or bits into analog signals for transmission at the sending end, and demodulates the analog signals to bits at the receiving end. Telephone modems enables data communication between two computers over voice – grade telephone lines. Purpose and Usage The computers are digital devices that are connected via analog local loops of the telephone networks. So, there is a need to convert the bits to analog signals so that they can be transmitted via the physical channels; and conversely convert analog signals in the ... Read More

In a telephone system, the local loop is a two-wire connection between the subscriber’s house and the end office of the telephone company. It is commonly referred to as the “last mile” of the telephone network. The loop may run from 1km to as far as 10 km.CompositionTraditionally, local loops are composed of twisted pair copper cables. The old local loops have several limitations − narrow bandwidth, high attenuation, distortion of symbols, crosstalk's etc.In recent times, copper wires are being replaced by fiber optic cables for faster and more accurate performance. Installation of fiber cables is popularly known as FttH ... Read More

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

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

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

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