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♦ Operating System ♦ OOPs concept ♦ Programming Languages Operating System A program that acts as an intermediate software(system) between a user of a computer and computer hardware. Resource allocator (allocation, management, withdrawal) Control Program Device Manager Functions of Operating System Process Management Process Management: Creation and deletion of process handled by CPU The synchronization and scheduling of processes also handle by CPU only. File Management Crating and deleting both the files and directives. Other functions of Operating system Allocating space for files Keeping backup securing easy access to file Input-output management Storage management User interface GUI CLI/ CUI Parts of OS Kernel : it is a computer program that manages input/ output requests from software and translates them into data processing instructions for the CPU. Shell : is a command line interpreter it interprets the commands the user types in and arranges for them to be carried out. Micro and Monolithic and hybrid are type of? Operating system Structure user User application system Application System Shell kernel Shell kernel hardware H/W Kernel and user mode Application User Mode System Libraries Kernel Mode interaction by system calls OS Device OS interacts with memory via load and store instructions and CPU registers OS: Spooling Spool: Simultaneous Peripheral Operation On-Line A spool is a buffer that holds output for a device such as printer that can not accept interleaved data streams The spooler may be reading the input of one job while printing the output of a different job. Process Management A process is a program in execution. It is a unit of work within the system. Program is a passive entity, process is an active entity Process needs resources to accomplish its task CPU Memory i/o Process state New admitted terminated interrupt exit ready running scheduler dispatch i/o event completion i/o event wait waiting Process Scheduling For maximizing CPU use, quickly switch process onto CPU for time sharing. Process scheduler selects among available processes for next execution on CPU. Maintains scheduling queues of processes Job queue- set of all process in system Ready queue- set of all processes residing in main memory, ready and waiting to execute Device queues – set of processes with an i/o device Bootstrap Loader It loads Operating system from Hard Disk to Main Memory Types of Operating System Single user OS Multi user OS Multitasking OS RTOS OS Embedded OS Time Sharing OS Batch Processing OS Distributed OS Mobile OS Server Site OS CPU Scheduling: CPU Scheduling is the process by which an Operating System decides which programs get to use the CPU. CPU scheduling is the basis of MULTIPROGRAMMED operating systems. By switching the CPU among processes, the operating system can make the computer more productive. CPU Schedulers: Schedulers are special system software’s which handles process scheduling in various ways. Their main task is to select the jobs to be submitted into the system and to decide which process to run. CPU scheduling algorithm 1. First Come First Serve (FCFS) Jobs are executed on first come, first serve basis. Easy to understand and implement. Poor in performance as average wait time is high. 2. Shortest Job First (SJF) Best approach to minimize waiting time. Impossible to implement Processer should know in advance how much time process will take. 3. Priority Based Scheduling Each process is assigned a priority. Process with highest priority is to be executed first and so on. Processes with same priority are executed on first come first serve basis. Priority can be decided based on memory requirements, time requirements or any other resource requirement. 4. Round Robin Scheduling Each process is provided a fix time to execute called quantum. Time uniformity maintained Once a process is executed for given time period. Process is preempted and other process executes for given time period. Context switching is used to save states of preempted processes. 5. Multi-Queue Scheduling Multiple queues are maintained for processes. Each queue can have its own scheduling algorithms. Priorities are assigned to each queue Language What is language? Language is an important element of Communication that may consist of either single or all the below mentioned components. Sound Expression Words Grammar etc Programming Language Programming language is formally designed language that is used to instruct a digital system. We have three types of programming language. Machine Language Assembly Language High level Language Scope of languages to CPU Low Level Assembly High Level CPU Translator Compiler Assembler Interpreter Assembler It is used to convert the assembly language which consist of mnemonics codes. compiler It converts source code into machine language. Compiler reads whole source code at a time. For each high level language a separate compiler requires. Interpreter It converts source code into machine language. Interpreter reads source code line by line and converts it into machine code OOPS Concept OOPS An object is basic unit of object oriented programming Approach which has a name and is designed to perform certain actions, it also interacts with other elements of program. Features of OOPS Class Object Encapsulation Polymorphism Data Hiding Data Abstraction Inheritance object Object is instance of class having some characteristics and behavior, object is a key to oops class Class is a collection of objects, in a general class may contain data and function It is collection of same type of object Automobile is a class that may contains two wheeler, four wheeler bull cart ? Inheritance Properties of acquiring features of predecessors In oops class inherits the property of it superior class Advantage Code reusability Less consumption of time Inheritance Single :subclass inherits properties of its super class Multiple : one subclass can inherit properties from multiple super class(ex. java) Multilevel: A subclass is inherited from existing subclass. Hierarchical: a single class act as a super class for more than one subclass. Data Abstraction Displaying only and essential data and hiding the background details. Data Hiding done by using access modifiers Public Private protected(internal method/ function) Encapsulation Wrapping data members and member function together in single unit Member function(Method) used to access the data hence provide add on security to the data Polymorphism The word polymorphism means multiple forms, in oops the polymorphism describes the implementation of single method in different manner Static dynamic example Area() triangle square cube Method overloading Method Overloading means a function having same name but different arguments/ parameters. Ex: add(int,int) add(int,int,int) add(int, float) add(float,float) int add(int a, int b) { Return a+b; } int add(double a, double b, double c) { Return a+b+c; } int main() { int z; double r; z=add(5,4); r=add(5,4,6); cout<<z”\n”<<r; } OUTPUT 9 15 Method overriding Allows subclass or child class to provide a specific implementation of method that is already provided by one of its super class or parent class. The implementation in the subclass overrides(replaces) the implementation in the super class by providing a method that has same name, same parameters and same return type as methods in parent class. Ex: class abc { Protected: Int x; Public: void get_x (int a) { x=a; } void put() { cout<<“X”<<x; } }; class xyz: public abc { int y; public: Void get (int a, int b) { x=a; y=b; } void put() { cout<<“X :”<<x; cout<<“Y :”<<y; } }; int main() { xyz a; a.get(5,10); a.put(); return 0 } Output: X: 5 Y: 10 An Integer variable that is used to manage concurrent processes is called….. (A) Thread (B) Semaphore (C) Counter (D) None of the above …… is the smallest unit for processing that consists of a program counter, a stack & a set of registers. (A) Compiler (B) Thread (C) Heap (D) None of the above Which of the following services is not supported by the OS? (A) I/O Operation (B) Protection (C) Compilation (D) None of the above First Come First Serve (FCFS) Scheduling is……. (A) used to reduce waiting time (B) easy to understand and implement (C) impossible to implement (D) None of the Above ……… is a system call of OS that is used to create a new process? (A) Shell (B) Kernel (C) Fork (D) Thread Which of the following is an example of Cooperative Multi-Tasking OS? (A) Lynx OS (B) Mac OS (C) MS DOS (D) None of the above The performance of Round Robin(RR) scheduling depends on…… (A) quantum. (B) priority. (C) preemption (D) None of the above Which of the following plays an important role in modern Operating Systems(OS)? (A) Kernel. (B) Shell (C) Fork. (D) None In DOS label command is used to…. (A) Create the label of disk (B) Change the label of disk (C) Both (A) & (B) (D) None Thank you