In C/C++, "static" variables mean a different thing to static variables in Java! How many objects can be created from an abstract class? What is the scope of an automatic variable?a) Exist only within that scope in which it is declaredb) Cease to exist after the block is exitedc) Exist only within that scope in which it is declared & exist after the block is exitedd) All of the mentioned Answer: cClarification: None. We also note that the main thread is not guaranteed to be a managed thread, so any library after the main thread isn't quite guaranteed to be able to identify it. What does it have to do with the assumption you accuse me of? A class's static initialization normally happens immediately before the first time one of the following events occur: an instance of the class is created, a static method of the class is invoked, a static field of the class is assigned, a non-constant static field is used, or. In Java, static variables are also called class variables. For static variables, an initialization can be made without generating code. The compiler checks for you, if the variable is definitly set. So to implicitly initialize a local variable the compiler would need to generate code without the programmer explicitly commanding it to do so, which is quite against that "philosophy". What are the differences between a pointer variable and a reference variable? you can visit and practice MCQ for your degree program of "Object Oriented Programming With C Top MCQs with answer practice . Home C Programming Objective Questions 250+ TOP MCQs on Automatic Variables and Answers. I wrote these following codes in Stack.h: I got the error: if I add a static keyword at line X, and initialize the variable outside the class de . Because the declaration for a non-inline static data member inside the class is not a definition.. OK, but why are static variables initialized to zero, and not some other value? In almost all cases it is easy to see whether a variable is assigned before use. @hacker, I want to know why exactly static variables are initialized by zero? When the initializer calls the current function recursively this check will be reached before the function has been initialized. This is just a guess, but it might be the way it is for statics since it's easy to implement, and useful. Learn competitive java programming mcq questions and answers on Data Types and Variables with easy and logical explanations Page-4 section-1. 2. It can access only other static members of its class. Why is processing a sorted array faster than processing an unsorted array? Which of the following statements are correct for a static member function?1. 250+ TOP MCQs on Automatic Variables and Answers, 250+ TOP MCQs on Automatic Variable and Answers Pdf OOPs, 250+ TOP MCQs on Signal vs Variables 1 and Answers, 250+ TOP MCQs on Scope and Lifetime of a Variable and Answers, 250+ TOP MCQs on Register Variables and Answers, 250+ TOP MCQs on Static Variables and Named Constants and Answers, 250+ TOP MCQs on Scope and Lifetime of Variables and Answers, 250+ TOP MCQs on External Variables and Answers, 250+ TOP MCQs on Automatic Control and Answers, 250+ TOP MCQs on Signal vs Variables 2 and Answers, 250+ TOP MCQs on Automatic Landing Systems and Answers, 250+ TOP MCQs on Default Variables and Answers, 250+ TOP MCQs on SQL Server Variables and Answers, 250+ TOP MCQs on Declarations and Answers, [CLASS 9] Maths Chapter 4 Linear Equations In Two Variables, 250+ TOP MCQs on Automatic Extraction Turbines and Answers. In all the languages C, C++, Java, the default initialisation of static variable is zero. If you want, you can clear that memory (zero it), but that would incur a runtime overhead. Most Asked Technical Basic CIVIL | Mechanical | CSE | EEE | ECE | IT | Chemical | Medical MBBS Jobs Online Quiz Tests for Freshers Experienced . a) Exist only within that scope in which it is declared b) Cease to exist after the block is exited c) Exist only within that scope in which it is declared & exist after the block is exited d) All of the mentioned Answer: c Clarification: None. Comparing Java enum members: == or equals()? You'd rather want it initialized to NULL than some random garbage. This has to do with the concept of "only pay for what you use" in C/C++. Site design / logo 2022 Stack Exchange Inc; user contributions licensed under CC BY-SA. In C#, static variables are initialized by the class loader when the class is first loaded. Why static global variables initialized to zero, but static member variable in class not initialized? We provide you study material i.e. Which of the following storage class supports char data type?a) registerb) staticc) autod) all of the mentioned Answer: dClarification: None. A single copy to be shared by all instances of the class. It is a variable which belongs to the class and not to object (instance) Static variables are initialized only once , at the start of the execution. Your email address will not be published. Effect of coal and natural gas burning on particulate matter pollution. Automatic variables are _________a) Declared within the scope of a block, usually a functionb) Declared outside all functionsc) Declared with the auto keywordd) Declared within the keyword extern Answer: aClarification: None. Does Java support default parameter values? But this didn't happen. a) automatic variableb) static variablec) register variabled) global variable Answer: aClarification: None. Yes! For local variables, none of these apply; they are allocated "on the fly" (typically on a stack) and it would be a waste of resources to clear them, since they're typically going to be assigned to very soon anyway. PDF's for offline use. We take free online Practice/Mock test for exam preparation. Each MCQ is open for further discussion on discussion page. All the services offered by McqMate are free. About Java, as far as I know, variables are always initialized when the program enters their scope, no matter if they are static or not. Automatic variables are initialized to ___________a) Zerob) Junk valuec) Nothingd) Both Zero & Junk value Answer: bClarification: None. And you can always initialize the variable explicitly. These variables will be initialized first, before the initialization of any instance variables; A single copy to be shared by all instances of the class; A static variable can be accessed directly by the class name and doesn't need any object. Why there are no global variables in Java. When would I give a checkpoint to my D&D party that they can return to if they die? 5. D. No need to initialize static variable. You can initialize a static object with a constant expression, or an expression that reduces to the address of a previously declared extern or static object, possibly modified by a constant expression. #include<iostream>. Why does my stock Samsung Galaxy phone/tablet lack some features compared to other Samsung Galaxy models? Why does the USA not have a constitutional court? Here is a listing of online C test questions on Automatic Variables along with answers, explanations and/or solutions: 1. yes I agreed that the memory of static variables is alllocated at link time, but why it is zero by default. But then, what should that value be? But the probable reasons for these decisions in Java are: In the case of local variables, it's also conceivable that a local variable could be declared (which at the bytecode/machine code level essentially means allocating stack space/moving the stack pointer) but then never actually written/read in a particular code path. class Test {. The static variables are alive till the execution of the program. QN: Which of the following is the best machine learning method? // variables inside a class. Both static and global variable behave same to the generated object code. Asking for help, clarification, or responding to other answers. Here is the syntax of static variables in C language, static datatype variable_name = value; Here, datatype The datatype of variable like int, char, float etc. What will be the x in the following C code? In many cases it can also rely on features of the operating system's executable file format, if that format supports "bss sections", which are cleared by the loader instead. 6. 1; B. Null; d. None of these; Answer. Why is the federal judiciary of the United States divided into circuits? Why is apparent power not measured in watts? Not the answer you're looking for? Actually, from the JVM point of view, the local variable simply doesn't exist until it is initialized. Copyright 2022 All Rights Reserved by McqMate, Electronics and Communication Engineering, Electronics and Telecommunication Engineering, Object Oriented Programming with C++ (OOP in C++), Object Oriented Programming with C++ (OOP in C++) solved MCQs. However, there are still ways of seeing the fields before assignments (not true with locals). Automatic variables are allocated memory in ___________ D. is same as an automatic variable but is placed at the head of the program. The compiler checks that final fields are assigned and not obviously used before assigned. That actually eases writing correct programs in the long run ;-). So, a static variable inside a class should be initialized explicitly by the user using the class name and scope resolution operator outside the class as shown below: // C++ program to demonstrate static. Treating the address of the object of the derived class as the address of the base class means, The variable that contains the address of constant or variable. The memory for them is allocated at link time, and the initial value for them is also provided at link time. As a result, class initialization will initialize static variables. static int a = m1 (); static. Why file scope static variables have to be zero-initialized? is initialized once at the commencement of execution and cannot be changed at run time. {. 2. System.out.println ("Inside static block"); } static int m1 () {. [Solved] A static variable is initialized to when the first object of its class is created. For more info, please refer to these other questions: Paragraph 8.5.6 of the C++ standard states that: "Every object of static storage duration shall be zero-initialized at program startup", (The standard also says that the initialization of local variables is undefined). Related C Programming MCQ with Answers. Which of the following is not used to seek a file pointer? But for simplicity, if you use the "initialize to 0" strategy, you don't have to inspect the individual members and check their types. (adsbygoogle = window.adsbygoogle || []).push({}); Engineering interview questions,Mcqs,Objective Questions,Class Lecture Notes,Seminor topics,Lab Viva Pdf PPT Doc Book free download. Explanation: No explanation is available for this question! These variables are allocated in . for local variables, giving them no default allows for the rule that forces the programmer to set some value before the variable is read, which can actually be useful in allowing the compiler to spot certain errors. Post your comment / Share knowledge Enter the code shown above: Please enter the code shown above Are there conservative socialists in the US? Why the static variables are deterministically initialized and local variables aren't? It has some other data members inside. As for c and c++, it's about programmers caring about their code effect and loving being in control. QN: PCA can be used for projecting and visualizing data in lower dimensions. For frequently called functions that may be a disaster. Help us identify new roles for community members, Proposing a Community-Specific Closure Reason for non-English content. Should teachers encourage good students to help weaker ones? B. last object of the class is created. The compiler checks for you, if the variable is definitly set. The static variable declaration only runs the initializer if the static variable has not been initialized. Object Oriented Programming With C Top MCQs with answer practice set, QN: Application of machine learning methods to large databases is called, QN: If machine learning model output involves target variable then that model is called as, QN: In what type of learning labelled training data is used, QN: In following type of feature selection method we start with empty feature set, QN: In PCA the number of input dimensiona are equal to principal components. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Engineering 2022 , FAQs Interview Questions. The class that is not used to create object. retains its value throughout the file of the program . Instead of letting the program fail if it accesses a non-initialized variable, it will be initialized implicit with null. It's not best solution, sure, but I don't know a better one. Connecting three parallel LED strips to the same power supply. Home Bachelor of Computer Applications (BCA) Object Oriented Programming with C++ (OOP in C++) A static variable is initializ. Object Oriented Programming With C Top MCQs with answer practice set. A static variable can be accessed directly . What happens when a class with parameterized constructors and having no default constructor is used in a program and we create an object that needs a zeroargument constructor? This assume that compilers are really dumb. It makes sense to initialize all of them to their default values. static or class variables (with an Object type) are initialized with null, because the compiler can't check if they are initialized at compile time. There is no runtime overhead. On the other hand, the memory for local variables is allocated at run time. What is the scope of an automatic variable? E. None of . Global and static variables are initialized to their default values because it is in the C or C++ standards and it is free to assign a value by zero at compile time. This has the interesting artifact of being on whatever thread first referenced the class. Should I give a brutally honest feedback on course evaluations? Static variables must be initialized before the program starts Variables that can be evaluated at compile time (those initialized by a constant expression) are const-initialized All other static variables are zero-initialized during static initialization constexpr forces the evaluation of a variable as a constant expression and implies const We do not currently allow content pasted from ChatGPT on Stack Overflow; read our policy here. What do the following phrases mean in C++: zero-, default- and value-initialization? QN: What characterize unlabeled examples in machine learning. Do non-Segwit nodes reject Segwit transactions with invalid signature? What answer are you looking for? McqMate.com is an educational platform, Which is developed BY STUDENTS, FOR STUDENTS, The only objective of our platform is to assist fellow students in preparing for exams and in their Studies throughout their Academic career. Variables with a native type can't get a null value, so non-local variables are initialized with 0 or false, as a fallback. I expanded my answer, hopefully it has the info you're interested in. But then it also has to be reliably initialized to something (preferably false). Is the order of variables defined by the standard? Ready to optimize your JavaScript with Rust? Stephen C, not so much performance as control over performance. A. retains its value throughout the life of the program. A local variable declaration with no storage class specified is by default _________a) autob) externc) staticd) register Answer: aClarification: None. Where is it documented? Static variable in a class is initialized when _____ . ;-). Connect and share knowledge within a single location that is structured and easy to search. variable_name This is the name of variable given by user. The only significant difference between them is that the scope of static variables is the entire program. He cites standard and I give you the reason behind it. Next when we are creating 5 objects of the class then value of x is updated each time and as static variables are global to class therefore each updation of x is reflected back to each object hence value of x is 5. If you see the "cross", you're on the right track. C. is initialized once at the commencement of the execution and cannot be changed at the run time. In contrast, a class's instance will initialize the instance variables (non-static variables). for static/member variables, if you're going to initialise them to something, then zero is a convenient value because (a) it's generally a suitable value to mean "not set to anything else special", and is the value you would have picked anyway in some cases such as counters; and (b) internally, it's likely that zero can be used for "special" values, notably to represent null in the case of an object reference. But then how do you know if it has been initialized? So to some extent these are just design decisions on the part of the language designers. Are the S&P 500 and Dow Jones Industrial Average securities? And the flip side is that default initialization of locals would result in a performance hit. A normal or auto variable is destroyed when a function call where the variable was declared is over. And why this is not true for local variables? And the C++ designers are more focused on performance than ease of writing correct programs. I have no idea about java and I doubt it's different for statics/locals in java. The object file contains the initial values for the variables in the data segment and when the OS loads the executable it loads and maps this data segment before the program starts executing. So not having a default avoids doing unnecessary work of setting a default in those cases. A class's __________ is called when an object is destroyed. A static variable . a. All the instances of a class share the class's static variables. static variable must be initialized before use. 2. Required fields are marked *. The compiler can co-allocate all the variables into one contigous memory area, and then either emit code (a single memset() call) to clear it before main() is called. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, Its not specific to language, but its all about concepts? You could create a static boolean variable. 4. Initialization of static variables. This saves space in the executable, you could have. Static variables are initialized only once , at the start of the execution. Which of the followings is/are pointer-to-member declarator? static or class variables (with an Object type) are initialized with null, because the compiler can't check if they are initialized at compile time. Why would Henry want to close the breach? Required fields are marked *. How about a pointer? An external variable is one_____. Automatic variables are allocated memory in ___________a) heapb) Data segmentc) Code segmentd) stack Answer: dClarification: None. Facebook | Twitter | Pinterest | Instagram Given that, the behavior is consistent among all of them. D. No need to initialize static variable. One should practice these Objective Questions and answers continuously for 2-3 months to clear Samsung interviews on C Programming language. And you always have paragraph 8.5.6 of the C++ standard which says "Every object of static storage duration shall be zero-initialized at program startup". And how is it going to affect C++ programming? Initializing local variables would imply execution of extra code each time program enters the scope. That is, they belong to a class and not a particular instance. For example, we can use static int to count a number of times a function is called, but an auto variable can't be used for this purpose. Note though that the assignment to the static . OMCQ.in | Maintained by Online MCQ Team As far as I found, there were articles about initializing a static variables in class templates. If you reject this, I'd expect you to accept Andreas' answer. However, Im using a normal class with member functio . What's the \synctex primitive? This is not really a technical requirement. The arrays of variable that are of the type class. Related Questions on C++ Programming Questions. About Us | Privacy Policy | Term & Condition | Contact Us B. cannot be initialized. They're essentially a tradeoff between what's likely to be convenient for JVM implementations and convenient for programmers. Contact for any suggestion, queries, claims and feedback. Debian/Ubuntu - Is there a man page listing all the version codenames/numbers? How are these two pieces of code different? rev2022.12.9.43105. Not sure what you want. 77. Report View more MCQs in Object Oriented Programming with C++ (OOP in C++) solved MCQs Discussion No Comments yet Name * You can quite easily explain why 0 is used (although indeed it sounds slightly arbitrary), but explaining -1 or 1024 seems to be even harder (especially that the variable may not be large enough to hold that value, etc). D. No need to initialize static variable. Well, you generally want to do something with that variable. I want to know why exactly static variables in C, C++ and Java are initialized by zero by default? Speaking for java: local variables must be initialized before you can access it, because it's a safety gain. If you declare a function as static then this keyword is not available in a static member function. N.B. You can just initialize the entire memory area to 0. We can create objects of the abstract class. cannot be initialized. This can be seen from static data member documentation:. You don't know what was there before. All static data is initialized when the first object is created. Find centralized, trusted content and collaborate around the technologies you use most. Your email address will not be published. for a top-level class, an assert statement lexically nested within . To subscribe to this RSS feed, copy and paste this URL into your RSS reader. 7. Answer c. 0. you can visit and practice MCQ for your degree program of Object Oriented Programming With C Top MCQs with answer practice set., Degree Question Identification Number QN6681, Your email address will not be published. Yes! As to why, the standard doesn't say ;) One guess is that it's reasonably easy to implement without any additional downsides. Follow on Social Media /OMCQin: These variables will be initialized first, before the initialization of any instance variables. For local variables there's no way to initialize them without code because they are not initialized once, they should be initialized every time you enter their scope; also they are allocated in the stack, and when the allocation occurs the initial value in the stack in the general case is simply what was there before (except those rare moments you grow the stack more than it has grown before). The C++ philosophy is "you don't pay for things you don't use", so it doesn't zero that memory by default. using namespace std; class GfG. Next when we are creating 5 objects of the class then value of x is updated each time and as static variables are global to class therefore each updation of x is reflected back to each object hence value of x is 5.advertisement 2. 1) A static int variable remains in memory while the program is running. The static keyword is only used with the declaration of a static member, inside the class definition, but not with the definition of that . Static variable in a class is initialized when _____ . Static variable in a class is initialized when _____ . Non-final static fields should be exceedingly rare (. Initialization of an ArrayList in one line, Improve INSERT-per-second performance of SQLite. This means that the initializer will be called multiple times. Which of the following means "The use of an object of one class in definition of anotherclass"? Why is this usage of "I've to work" so awkward? C++11 introduced a standardized memory model. C. first object of the class is created. A. every object of the class is created. _________ used to make a copy of one class object from another class object of the sameclass type. The semantics of initialization could still be considered sane if the default value is something other than 0, but still deterministic. QN: Data used to build a data mining model. what about a class object, sure its constructor won't be called at link time, then if it is initialized in link time, it is just initialized as a POD, which seems make no sense? By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. And not only performance. C helps anyone preparing for Samsung and other companies C interviews. During dynamic memory allocation in CPP, new operator returns _________ value if memory allocation is unsuccessful. 3. local variables must be initialized before you can access it, because it's a safety gain. value Any value to initialize the variable. C. first object of the class is created. Answer: c Clarification: Static function can be called without using objects therefore the first call is fine. For example below program prints "1 2" 3. How about a struct/record? The stack has to grow. ANSWER: C 78. No, Ton, static variables are default-initialized. Explanation: Static function can be called without using objects therefore the first call is fine. If you do not explicitly initialize a static (or external) variable, it will have a value of zero of the appropriate type, unless it is a pointer, in which . He probably wants to know why this choice was made. Thanks for contributing an answer to Stack Overflow! Was the ZX Spectrum used for number crunching? B. last object of the class is created. See how the static variables are implemented. Disclaimer: This is educational blog and don't claim any copyright material. Is it cheating if the proctor gives a student the answer key by mistake and the student doesn't report it? Below is the java program to demonstrate that static block and static variables are executed in the order they are present in a program. why global variable in C takes zero as initial value? More Related Questions on C++ Programming Questions. and the executable would not grow by a megabyte. It can be called using the class name, instead of objects. Would it be possible, given current technology, ten years, and an infinite amount of money, to construct a 7,000 foot (2200 meter) aircraft carrier? Well written ,but thats not an answer to my question. QN: What does dimensionality reduction reduce? Static members exist as members of the class not as an instance of the class. Default value of static variable is_____ . {. Solution by Mcqs Clouds Answer: Option C Explanation: No explanation is available for this question! A static variable is one that_____. What does it mean? A static variable is initialized to -when the first object of its class is created. @Tom - The answer to your "open" question is that it would be exceedingly difficult to come up with JLS rules for this that 1) don't require analysis of all classes in a program, and 2) cope with dynamic loading. 55) The statement # include is written at the top of a program to indicate I repeat, though, these are design decisions to some extent. To learn more, see our tips on writing great answers. Learn competitive java programming mcq questions and answers on Data Types and Variables with easy and logical explanations Page-4 section-1 . A. every object of the class is created. 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