Found 494 Articles for Computer Engineering

Secondary storage devices are non-volatile devices where the data is stored for long-term storage. Disks are the mainly used secondary storage devices. They provide the bulk of secondary storage in operating systems today.The main activity that is performed in secondary storage management is disk scheduling. There are many disk scheduling algorithms. However, the important ones are FCFS scheduling, SSTF scheduling, SCAN scheduling and LOOK scheduling.All the disk scheduling algorithms are explained using the following requests for the disk -10, 95, 23, 78, 80First Come First Served SchedulingIn first come first served scheduling, the requests are serviced in their coming order. ... Read More

System programs provide an environment where programs can be developed and executed. In the simplest sense, system programs also provide a bridge between the user interface and system calls. In reality, they are much more complex. For example, a compiler is a complex system program.System Programs PurposeThe system program serves as a part of the operating system. It traditionally lies between the user interface and the system calls. The user view of the system is actually defined by system programs and not system calls because that is what they interact with and system programs are closer to the user interface.An ... Read More

The operating system is split into various layers In the layered operating system and each of the layers have different functionalities. This type of operating system was created as an improvement over the early monolithic systems. Why Layering in Operating System? Layering provides a distinct advantage in an operating system. All the layers can be defined separately and interact with each other as required. Also, it is easier to create, maintain and update the system if it is done in the form of layers. Change in one layer specification does not affect the rest of the layers. Each of ... Read More

The entire operating system works in the kernel space in the monolithic system. This increases the size of the kernel as well as the operating system. This is different than the microkernel system where the minimum software that is required to correctly implement an operating system is kept in the kernel.A diagram that demonstrates the architecture of a monolithic system is as follows −The kernel provides various services such as memory management, file management, process scheduling etc. using function calls. This makes the execution of the operating system quite fast as the services are implemented under the same address space.Differences ... Read More

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

Code division multiplexing (CDM) is a multiplexing technique that uses spread spectrum communication. In spread spectrum communications, a narrowband signal is spread over a larger band of frequency or across multiple channels via division. It does not constrict bandwidth’s digital signals or frequencies. It is less susceptible to interference, thus providing better data communication capability and a more secure private line. Code Division Multiple Access When CDM is used to allow multiple signals from multiple users to share a common communication channel, the technology is called Code Division Multiple Access (CDMA). Each group of users is given a shared code ... Read More