In passband transmission, the amplitude, phase or frequency of the carrier signal is regulated to transmit the bits. The incoming data stream is modulated onto a carrier and then transmitted over a band-pass channel. The types of passband transmission are illustrated as − Amplitude Shift Keying (ASK) In ASK, the amplitude of the signal is varied to represent the signal levels, while frequency and phase remains constant. In order to represent 0 and 1, two different amplitudes are used. Frequency Shift Keying (FSK) In FSK, the frequency of the signal is modulated to represent the signal levels, while ... Read More

In baseband transmission, the data bits are directly converted into signals. Generally a higher voltage level represents the bit 1, while a lower voltage level represents bit 0.The different encoding schemes are shown in the diagram. Among these, the first three are come in the category of polar encoding. In polar signaling, one logical state is represented by only one voltage state. In bipolar schemes, two voltage levels may be used to represent a logical state.NRZ (Non – Return to Zero)NRZ is an unipolar coding scheme. Here, a high voltage represents 1, while a low voltage represents 0. Non-return to ... Read More

Fiber optic communications and satellite communications are complementary to each other. Their properties are very different from one another and consequently their usage varies.Comparison between satellite communication and optical fiber communication can be done based upon the following areas −TerrainSatellite communication is best suited for rough terrains, poorly connected areas and places where it is difficult to lay wires.On the other hand, fibers are suited for urban areas with good infrastructures, where it is convenient to lay communication lines.BandwidthFiber optic promises extremely higher bandwidth with negligible electromagnetic interference. Satellites have lesser bandwidth and are prone to interferences.Data Rate and DelayThe ... 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

Mobile Computing deals with human computer interaction using mobile devices. It contains mobile hardware and software as well as mobile computing devices. A mobile computing infrastructure usually uses ad-hoc networks and communication protocols. This is considerably different than a traditional computing structure as it uses fixed topology and protocols.An image describing mobile computing architecture is as follows −As seen above, the mobile computing architecture contains various mobile devices such as mobile phones, mobile tablets, laptops etc. These devices are connected to the mobile network which is a part of the internet. All the data is linked to cloud computing data ... Read More

Disks are the mainly used mass storage devices. They provide the bulk of secondary storage in operating systems today.Disk StructureEach modern disk contains concentric tracks and each track is divided into multiple sectors. The disks are usually arranged as a one dimensional array of blocks, where blocks are the smallest storage unit.Blocks can also be called as sectors. For each surface of the disk, there is a read/write desk available. The same tracks on all the surfaces is known as a cylinder.Disk SchedulingThere are many disk scheduling algorithms that provide the total head movement for various requests to the disk. ... Read More

Storage management plays an important part in operating system. It deals with the storage procedures in the computer system using an operating system. Details about this is as follows −Memory ManagementMemory management plays an important part in operating system. It deals with memory and the moving of processes from disk to primary memory for execution and back again.The most important concepts in memory management are paging and segmentation. Details about these topics are given below −PagingIn a computer system, virtual memory can be created that is more than the actual memory available i.e. physical memory. To implement this, the concept ... Read More

Files are used to provide a uniform view of data storage by the operating system. All the files are mapped onto physical devices that are usually non volatile so data is safe in the case of system failure.File AttributesThe attributes of a file may vary a little on different operating systems. However, the common file attributes are −NameThis denotes the symbolic name of the file. The file name is the only attribute that is readable by humans easily.IdentifierThis denotes the file name for the system. It is usually a number and uniquely identifies a file in the file system.TypeIf there ... Read More

Open Source operating systems are released under a license where the copyright holder allows others to study, change as well as distribute the software to other people. This can be done for any reason. The different open source operating system available in the market are −CosmosThis is an open source operating system written mostly in programming language C#. Its full form is C# Open Source Managed Operating System. Till 2016, Cosmos did not intend to be a fully fledged operating system but a system that allowed other developers to easily build their own operating systems. It also hid the inner ... Read More