Basic Data Structure Programs In C Pdf: full version free software download. Basic Data & Shareholder Structure. Basic Data International. Basic program structure. We will start right away with a look at a Java program. For most of this course all your programs will have the same basic structure, which is reproduced below. Using Classes and Structures in Visual Basic.NET. A class or structure can contain data members to hold these items and code members to manipulate them. BizSpark (for startups) DreamSpark. Using Classes and Structures in Visual Basic . NET. You can review the basic points of comparison between the two types in the . Data Structure Code Examples. These are some data structures, with a simple test environment, that are based on my book. Chapter 1; An array-based stack. A block-list-based stack. Where can I get Data Structures interview questions and answers with explanation? A data structure is a way of organizing data that considers not only the items stored, but also their relationship to each other. To find this topic, start Visual Studio . NET, select Index from the Help menu, and type . A container type is useful for gathering a set of data items, such as customer information, that is closely related but cannot be held in a single elementary type. A class or structure can contain data members to hold these items and code members to manipulate them. The members can then be referred to individually, or the container can be treated as a single entity. The common language runtime allows value types to have most of the same functionality as reference types. Visual Basic . NET exposes this capability by unifying the syntax for classes and structures. Superficially, the two types appear so similar that an application developer might not know which one is better for a given situation. Underneath the surface, however, significant differences can make the choice important. Storage Consumption. Unless your application creates a large number of container types, the storage differences between class and structure instances are not likely to be significant. But it is still useful to understand how these types use memory. Data Members. Because classes are reference types, an object variable uses only four bytes directly. These bytes point to the class instance data, which occupies memory elsewhere. Therefore, the overall storage consumption of an object variable is slightly greater than that of a structure variable with the same members. Because structures are value types, a structure variable consumes at least the sum of the memory requirements of its data members. Regardless of the number of instances of a particular class or structure type, each code member is stored in memory only once. Therefore the existence or size of code members is not a consideration in the choice between a class and a structure. Copies of Variables. A variable is copied when it is assigned to another variable, when it is passed to a procedure By. Val, and when it is returned from a Function procedure. Visual Basic performs shallow copies, which means that it copies only the contents of a variable, and not any data to which those contents might refer. Therefore, a copy of a reference type variable duplicates only the four- byte pointer, and both the original and the copy point to the same data in memory. A copy of a value type variable replicates its entire contents in each new instance. Independent Instances. Two Object variables can point to the same class instance, but two structure variables are always isolated from each other. If you need the ability to change the data through one variable and access the changed values through another variable, you must use class instances. Performance. Reference types are managed on the heap, value types on the stack. There is a performance overhead for heap allocation, object access, and garbage collection, so class instances are less efficient than structure instances in this respect. The speed difference, which depends on many factors such as platform, loading, and data size, can range from unnoticeable to enormous. Array Elements. Because an array is a reference type, its elements are all allocated on the heap, whether they are value or reference types. However, an array of value types is allocated contiguously, which improves locality of reference and reduces the risk of processor cache misses. Consequently, there is a preference for structures over classes as array elements. Boxed Value Types. If you define a value type but subsequently treat it as an object, it must be boxed, or converted to type Object. The common language runtime boxes a value type instance by making a copy of it, embedding it in a newly allocated object, and storing pointers to its type information in the metadata. You treat a structure as an object if you assign it to an Object variable or pass it to a procedure that takes an Object argument. If you do this, the common language runtime must box it and often unbox it, as well as manage it on the heap. This kind of treatment can make a structure considerably less efficient than if you had created it as a class in the first place. A Visual Basic . NET Collection object stores all its elements as type Object. Therefore, if you use structures as the elements of such a collection, you incur overhead for boxing and unboxing. An array of structures is already a reference type, so it does not undergo boxing when assigned or passed to an Object. Data Types and COM Interop. A COM interop application makes calls between managed code and unmanaged code (COM). If your application does this, the data types of the arguments you pass can affect performance. Fewer and smaller arguments often result in greater speed, but the interop compatibility of their data types can also make a difference. A data type is blittable if it has the same representation in both managed and unmanaged memory. This allows it to be copied across the managed/unmanaged boundary without conversion. The blittable types in Visual Basic . NET are Byte, Short, Integer, Long, Single, and Double. The common language runtime types SByte, UInt. UInt. 32, and UInt. If you can limit your data members to these types, you can improve performance for both classes and structures. However, the improvement is more pronounced with structures because a structure of all blittable members is itself blittable. Data Size. If your application makes a large number of copies of a variable, the memory required for that variable can be a factor that determines whether it should be a value type or a reference type. There is a trade- off between copying all the bytes of a value type as opposed to allocating a new reference type on the heap. The more copies of a variable your application makes, the more important this distinction becomes. A theoretical observation might serve as an initial guideline. Suppose you write a test application that does the following. Defines a structure and a class with identical data members, thus giving them a common data size. Declares two structure variables and two object variables representing instances of the structure and the class respectively. Executes a tight loop copying one structure variable to the other a large number of times. Executes another tight loop copying one object variable to the other the same number of times. Depending on the execution platform and the loading from other tasks, you are likely to observe the following. If the common data size is less than 1. If the data size is 1. If the data size is greater than 1. As the data size increases, there is eventually a point at which the class loop is significantly faster than the structure loop. Even allowing for variations due to platform and loading, large data sizes are likely to be more efficient when defined in classes. Note. If a significant portion of your application involves copying such variables, the guideline might be a useful predictor. Experimentation. There are so many factors affecting the relative performance of classes and structures that it is almost impossible to make a general recommendation. The ultimate decision depends on the unique characteristics of your application. This suggests that it might be worthwhile to experiment during development. You can sometimes define a container type as either a Class or a Structure. When this is the case, you might be able to develop your application using one type, measure the overall performance, and then change to the other type and measure performance again. This approach is not possible if you use inheritance or generalized constructors, and it is not practical if you use multiple variables to refer to the same instance. Event Handling. You can declare and raise an event in either a class instance or a structure, and you can declare a delegate in either type. However, while classes support full event handling, structures are more limited. The With. Events and Handles keywords set the connection between an event and its handlers at compile time. They are simple to design and write, but you cannot change the connection at run time. You can specify these keywords inside a class but not in a structure. The Add. Handler and Remove. Handler statements operate at run time and are more flexible than With. Events and Handles. A structure can use Add. Handler to make one of its procedures an event handler, provided it is a Shared. Sub procedure. By contrast, a class can use Add. Handler with either an instance procedure or a Shared. Sub procedure. Structure Example. The following example defines a structure to hold a complex number and perform some basic operations on it. The data members consume only 1. Therefore this complex number type is a good candidate for a structure instead of a class. Even though they do not define any procedures, these container types make use of inheritance and polymorphism. The only way to define such a data architecture is to use classes. Classes are more flexible than structures, and the storage and performance differences are often negligible. Structures are intended primarily for types that behave like built- in types, not necessarily for general- purpose use. Additional Resources. The following resources, which are part of the Visual Studio . NET documentation, provide additional information about structures and classes.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. Archives
December 2016
Categories |