It combines the power of assembly with the flexibility and high-level features of an interpreted language. It has since become famous for other uses, such as web development and video game design.
Let us C by Yashavant Kanetkar — Yashavant Kanetkar is an Indian-born computer scientist who is well-known for his work on programming languages. He also gives talks on a variety of technological topics and writes essays for magazines like Developer 2. In the previous three decades, Yashavant Kanetkar has developed, moulded, and nourished thousands of IT professions. For C language programmers, it is must to master the complexity of the language to deal with programming software in engineering, gaming and other fields.
In order to understand each concept of the C language, it is necessary to follow a good reference book in easy-to-understand text. It covers various topics that could be easily understood with the help of examples given with each programming concept.
No other casting between user-defined classes is allowed. However, pointers to different classes can be cast to each other without any restrict. What is passed in the casting is only the address. So you can cast a pointer to an integer to a Employee-class pointer.
Then the Employee pointer will just assume that starting from the passed address it can find all attributes of Employee class. From now on we will talk more about OO issues. As a class, it combined the data attributes and the behavior attributes of an object together, and formed an object which can simulate both aspects of a real-world object.
To distinguish independent functions such as those string handling functions in "string. The "public:" and "private:" labels are called "member access specifiers". All data members and methods declared by the "public" specifier are accessible from outside, and all declared by "private" are only accessible for methods.
Actually an object contains only the data members. Methods do not belong to any specific object. The belong to the class.
All objects share one copy of methods. It may improve the performance, but it is not good for information hiding, because the client of the object is able to "see" the implementation of its methods. If a method is defined outside the class body, you have to use keyword "inline" if you want it to be inlined.
Only the simplest methods can be defined inside the class body. To define the method outside the class body, you have to use scope resolution operator "::", which we have used before to access global variables, when a local variable with the same name had been declared.
Use "class name::" in front of the method definition to make it unique, because other classes may have methods of the same name. Methods which changes the data members are sometimes called "commands", and methods which do not change are called "queries".
Separating the commands and queries leads to simpler, more flexible and easy-understanding interfaces. There is no return type even not void for this special method. Default arguments are recommended for constructors so that even if no arguments are passed to the object the data members can still be initialized to a consistent state. STL containers requires the objects to have default constructors. Constructor can be overloaded. Normally three kinds of constructors are needed: 1.
Default constructor: no arguments; 2. Constructor: object; has all arguments to construct an unique 3. Copy constructor: has an argument its own type, to copy a new object out of it. The default constructor and normal constructor can be merged into one if the normal constructor uses default arguments. If no constructor is provided, the compiler automatically insert a default constructor. This default constructor does not perform any operation.
So the data members of the object may not be consistent. Built-in types are not initialized when created. When you call this method, if you pass a "Parent" object instead of "Child", the compiler will implicitly call the one-argument constructor and convert the "Parent" object to "Child". If you want to have an array of objects that do not have a default constructor, the work-around is to have an array of pointers and initialize them using operator new.
If copy constructor is not provided, compiler will provide a default copy constructor, which makes default memberwise copy, which can not deal with objects with pointer members.
There are two rules for the parameter of copy constructor: 1. Otherwise the copy constructor call results in infinite recursion, because for call-by-value, a copy of the object passed to the copy constructor must be made, which results in the copy constructor being called recursively. The object argument passed to the copy constructor must be constant. Otherwise it can not be applied on constant object.
Independent functions have file scope. Data members and methods are directly accessible by other methods of the same class. So two kinds of variables may appear in a method: local variables with block scope which is destroyed after the call, and data members.
Public members of a class is designed to be an interface for its clients. This helps to hide implementation details from the clients, reducing bugs and improving program modifiability.
Because of this, the use of "friends" is deemed by some people to be a violation of information hiding. Both structures and classes have private, public and protected access. Default of classes is private, default for structure is public.
They can also translate the data format used internally during implementation into the format for clients. Stack memory resources held by the object such as its compilercreated members are released automatically when the object leaves scope or explicitly deleted. A destructor is only needed to release resources which can not be automatically released, such as dynamically allocated memory using "new" or network or database connection.
Although writing the same statements again can avoid a method call and thus good for performance, it is bad for maintenance, because once the program need to be changed both places should be changed meantime.
Extra attention should be paid to always keep them identical. So always use a method call to avoid repeating code. For automatic local objects, constructors are called when execution reaches the point where the objects are declared. Destructors are called when the objects leave scope i. For static local objects, constructors are called only first time when the execution reaches the point where the objects are declared. It is the same in Java. For objects without dynamic members i. But for objects containing pointers to other objects, a default memberwise copy will only point the pointers of the two objects to the same other object.
This is called shallow copy. It is the same as default memberwise copy. Therefore, copy constructor is a must for any class which needs deep copy that default memberwise copy can not achieve. Copy constructor is therefore given big importance and becomes one of the four elements of the OCF: all classes should provide their properly implemented copy constructors.
In Java, because all objects are passed by reference and the language even does not support automatic pass-by-value, there is no need for enforcement of copy constructors.
For the purpose of cloning objects, Java provides a more robust and automated facility — the clone mechanism. Factory Method A factory method is a method which uses dynamic memory allocation to clone itself and return a pointer to the new copy. Suppose you have a abstract class Shape and a series of derived concrete classes such as Circle, Square, Rectangle, etc. Suppose you have a method which receives a concrete-class object with a Shape handle and do something on it.
You will lose all information of the derived-class part of data. It can not be modified, and only constant methods can access it. Non-constant methods can not access constant members, even if they do not modify the objects. Declaring an object to be constant not only can prevent it from being modified, it is also good for performance: today's sophisticated optimizing compilers can perform certain optimizations on constants, but can not do it on variables.
If you return this constant argument back, but did not declare the return type constant, the compiler will complain. Declaring the return by reference constant is to prevent the client from accessing the private data member through the reference. If a method returns one private data member by reference, the client who calls this method can modify reversibly this member.
A constant method can not modify any data member. It still can modify received arguments and local variables. When a constant object is created out of a class, all its nonconstant methods are forbidden to be called by the compiler. In the following example, compiler will prompt error on method call "t1. Member initializers must be used to initialize constant data members. A list of initializers start with a " : " after the constructor header, speparated by ",".
When a parent object is created, the member objects are created first, then they are used to construct the parent object. The order of the creation of member objects is decided by the order they are declared in the class definition, not the order of their member initializers.
Member objects do not have to be initialized explicitly. Not providing a default constructor for the class of a member object when no member initializer is provided for that member object is a syntax error. Member objects still keep their privacy from their owner. Owner class's methods can not directly access their private data members. Member objects are also called servers, and owners called clients. If a member object is initialized in the constructor with an assignment operator, its default constructor will be called first, then its assignment operator.
If it is initialized with initializer, only its constructor will be called. It is not only the matter of saving one method call, but also the matter of safety. For a class without a properly implemented default constructor or assignment operator, using assignment operator to initialize it may cause unexpected logic errors such as shallow copy.
A function can not declare itself to be a friend of a class. To be able to access a class, this independent function should usually receive an argument of that class, so that it can use the passed handle. When we call an independent function such as "test int i ", we say test1 ; But when we call a method test of object o1, we have to call through this object's handle: o1. When the compiler sees a method call, it implicitly convert it to add one more argument - the object through which the method is called, so that the method knows which object to access.
You can use it to access the object. When you say int a; int b[]; float b; Employee c; The compiler reads the type definition of the object for object c it is the class definition of class Employee and knows the size of the object. Therefore it will complain.
It is also not responsible for initializing the allocated memory. So usually there is a memset function call after malloc to initialize it explicitly. It reads the type definition and allocate exactly the amout of memory needed to hold the object of the given type, then it calls the constructor of that type to initialize the object. Therefore, malloc is the most flexible way to allocate memory, for it does the least thing for you and leave you with all freedom.
But it is also error-prone. Besides, C-style function memset may breach the encapsulation law. It can directly access private data members of an object. It calls the destructor of the type before freeing the memory. So for the sake of performance, if you can decide the size of the memory, always allocate memory at compile time using declarations.
Local objects created by declaration is discarded after leaving scope, but objects created by dynamic memory allocation is not destroyed after leaving scope. If not deleted it exists until the end of run. It is still pointing to the same memory location which has now been reclaimed by the OS. Therefore, if you delete it again the OS will shut down your program, because you are trying to delete something in the OS's territory.
Therefore, to prevent somebody or even yourself from accidentally deleting a pointer after it has already been deleted, assign 0 to a pointer after deleting it. Then the object itself including all its data members are destroyed and memory released to the OS. It is the one who created an instance of this class on the heap who is responsible for deleting this object, not the object itself, because the object can only be deleted when it is created on the heap, and the code in the class implementation has no way to know whether each instance of itself is created on the heap or stack.
It has the same effect as when a client deletes this object. Consider the following example. Delete ; but there will be a run-time error, because inside Delete function we are still deleting a statically-created object. Disclaimer: Sarkari Rush does not own books pdf, neither created nor scanned.
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