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OS_FAQ

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OS FAQ 1) What are the basic functions of an operating system? Operating system controls and coordinates the use of the hardware among the various applications programs for various uses. Operating system acts as resource allocator and manager. Since there are many possibly conflicting requests for resources the operating system must decide which requests are allocated resources to operating the computer system efficiently and fairly. Also operating system is control program which controls the us
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    OS FAQ 1) What are the basic functions of an operating system?Operating system controls and coordinates the use of the hardware among the variousapplications programs for various uses. Operating system acts as resource allocator andmanager. Since there are many possibly conflicting requests for resources the operatingsystem must decide which requests are allocated resources to operating the computer system efficiently and fairly. Also operating system is control program which controls theuser programs to prevent errors and improper use of the computer. It is especiallyconcerned with the operation and control of I/O devices.2) Explain briefly about, processor, assembler, compiler, loader, linker and the functionsexecuted by them.Processor:--A processor is the part a computer system that executes instructions .It is alsocalled a CPUAssembler: --An assembler is a program that takes basic computer instructions andconverts them into a pattern of bits that the computer's processor can use to perform its basic operations. Some people call these instructions assembler language and others usethe term assembly language.Compiler :---A compiler is a special program that processes statements written in a  particular programming language and turns them into machine language or code that acomputer's processor uses. Typically, a programmer writes language statements in alanguage such as Pascal or C one line at a time using an editor. The file that is createdcontains what are called the source statements. The programmer then runs the appropriatelanguage compiler, specifying the name of the file that contains the source statements.Loader:--In a computer operating system, a loader is a component that locates a given program (which can be an application or, in some cases, part of the operating systemitself) in offline storage (such as a hard disk), loads it into main storage (in a personalcomputer, it's called random access memory), and gives that program control of thecomputeLinker: --Linker performs the linking of libraries with the object code to make the objectcode into an executable machine code.3) What is a Real-Time System?A real time process is a process that must respond to the events within a certain time period. A real time operating system is an operating system that can run real time processes successfully 4) What is the difference between Hard and Soft real-time systems?  A hard real-time system guarantees that critical tasks complete on time. This goalrequires that all delays in the system be bounded from the retrieval of the stored data tothe time that it takes the operating system to finish any request made of it.A soft real time system where a critical real-time task gets priority over other tasks andretains that priority until it completes. As in hard real time systems kernel delays need to be bounded5) What is the important aspect of a real-time system or Mission Critical Systems?A real time operating system has well defined fixed time constraints. Process must bedone within the defined constraints or the system will fail. An example is the operatingsystem for a flight control computer or an advanced jet airplane. Often used as a controldevice in a dedicated application such as controlling scientific experiments, medicalimaging systems, industrial control systems, and some display systems.Real-Timesystems may be either  hard  or   soft  real-time.Hard real-time:-> Secondary storage limited or absent, data stored in short term memory, or read-onlymemory (ROM)-> Conflicts with time-sharing systems, not supported by general-purpose operatingsystems.Soft real-time:->Limited utility in industrial control of robotics->Useful in applications (multimedia, virtual reality) requiring advanced operating-system features.6) What is hard disk and what is its purpose?Hard disk is the secondary storage device, which holds the data in bulk, and it holds thedata on the magnetic medium of the disk.Hard disks have a hard platter that holds the magnetic medium, the magnetic medium can be easily erased and rewritten, and a typical desktop machine will have a hard disk with acapacity of between 10 and 40 gigabytes. Data is stored onto the disk in the form of files.7) What is virtual memory?A virtual memory is hardware technique where the system appears to have more memorythat it actually does. This is done by time-sharing, the physical memory and storage partsof the memory one disk when they are not actively being used.8) What are the difference phases of software development or software life cycle?  Ans Specification of the task Design of algorithmsImplementation (coding)  Testing and debugging  Maintenance and evolution of the systemObsolescence9) What is cache memory?Cache memory is random access memory (RAM) that a computer microprocessor canaccess more quickly than it can access regular RAM. As the microprocessor processesdata, it looks first in the cache memory and if it finds the data there (from a previousreading of data), it does not have to do the more time-consuming reading of data fromlarger memory.10) Differentiate between Complier and Interpreter?An interpreter reads one instruction at a time and carries out the actions implied by thatinstruction. It does not perform any translation. But a compiler translates the entireinstructions.11) Describe different job scheduling in operating systems.Scheduling is the activity of the deciding when process will receive the resources theyrequest.FCFS: --- FCSFS stands for First Come First Served. In FCFS the job that has beenwaiting the longest is served next.Round Robin Scheduling: ---Round Robin scheduling is a scheduling method where each process gets a small quantity of time to run and then it is preempted and the next processgets to run. This is called time-sharing and gives the effect of all the processes running atthe same timeShortest Job First: -- The Shortest job First scheduling algorithm is a nonpreemptivescheduling algorithm that chooses the job that will execute the shortest amount of time.Priority Scheduling: ---Priority scheduling is a scheduling method where at all times thehighest priority process is assigned the resource.12) What are different tasks of Lexical Analysis?The purpose of the lexical analyzer is to partition the input text, delivering a sequence of comments and basic symbols. Comments are character sequences to be ignored, while basic symbols are character sequences that correspond to terminal symbols of thegrammar defining the phrase structure of the input13) Why paging is used?Paging is solution to external fragmentation problem which is to permit the logicaladdress space of a process to be noncontiguous, thus allowing a process to be allocating physical memory wherever the latter is available.14) What are the main difference between Micro-Controller and Micro- Processor?  A microcontroller is by definition a is a computer on a chip. It includes all the necessary parts (including the memory) all in one IC. You just need to apply the power (and possibly clock signal) to that device and it starts executing the program programmed to it.A microcontroller generally has the main CPU core, ROM/EPROM/EEPROM/FLASH,RAM and some necessary functions (like timers and I/O controllers) all integrated intoone chip. The srcinal idea behind the microcontroller was to limit the capabilities of theCPU itself, allowing a complete computer (memory, I/O, interrupts, etc) to fit on theavailable silicon real estate.Microcontrollers are typically used where processing power isn't so important. Moreimportant are generally compact construction, small size, low power consumption andthat those chips are cheap. For example controlling a microwave oven is easilyaccomplished with the smallest of microcontrollers. There is countless number of smallelectronic devices which are nowadays based on microcontroller. A modern home caninclude easily tens or hundreds of microcontrollers, as almost every modern device whichhas electronics have a microcontroller (or more than one) inside.Microprocessor is generally just the CPU core itself, although nowadays it might havesome accessory parts also integrated to the same chip15) What is Context Switch?Switching the CPU to another process requires saving the state of the old process andloading the saved state for the new process. This task is known as a context switch.Context-switch time is pure overhead, because the system does no useful work whileswitching. Its speed varies from machine to machine, depending on the memory speed,the number of registers which must be copied, the existed of special instructions(such asa single instruction to load or store all registers).16) What is an Operating System?A program that acts as an intermediary between a user of a computer and the computer hardware.Operating system goals:Execute user programs and make solving user problems easier.Make the computer system convenient to use. Use the computer hardwarein an efficient manner 17) What is DRAM? In which form does it store data?DRAM is the Hershey's chocolate of readable/writable memory: it's not the best, but it'scheap, does the job, and is available almost everywhere you look. DRAM data resides ina cell made of a capacitor and a transistor. The capacitor tends to lose data unless it'srecharged every couple of milliseconds, and this recharging tends to slow down the performance of DRAM compared to speedier RAM types.18) Parallel Systems?
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