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Gregory Abramov
Gregory Abramov

Pointers On C

Pointers in C are easy and fun to learn. Some C programming tasks are performed more easily with pointers, and other tasks, such as dynamic memory allocation, cannot be performed without using pointers. So it becomes necessary to learn pointers to become a perfect C programmer. Let's start learning them in simple and easy steps.

Pointers on C

The actual data type of the value of all pointers, whether integer, float, character, or otherwise, is the same, a long hexadecimal number that represents a memory address. The only difference between pointers of different data types is the data type of the variable or constant that the pointer points to.

Designed for professionals and advanced students, Pointers On C provides a comprehensive resource for those needing in-depth coverage of the C programming language. An extensive explanation of pointer basics and a thorough exploration of their advanced features allows programmers to incorporate the power of pointers into their C programs. Complete coverage, detailed explanations of C programming idioms, and thorough discussion of advanced topics makes Pointers On C a valuable tutorial and reference for students and professionals alike.

It is not a book about pointers despite the title and the cover (I feel sure that I have seen that picture used on another, ghastly, book on C). This is a book about programming in C. The author starts in straight away. No time is wasted explaining what a computer is, or giving you a history lesson on the origins of C.

The author thinks that pointers are an extremely important aspect of C and uses understanding of their use as a unifying theme. On the other hand he is quite willing (sensibly in my opinion) to tell you to do some things now and wait for the explanation till later. He introduces the address of operator as a simple requirement for reading values into scalar variables with

That's way too much pointers you have, I must say. Having simply std::list myList; is perfectly fine and will save you a great deal of headache when the time comes to tracking down and destroying all the objects.

There are many good C books on the market; why do we need another one? In my ten years of teaching a college-level course on C programming, I have yet to find a book that covers pointers the way I would like. Many books cover pointers in a single chapter dedicated to the topic, often late in the book.

It is not enough to describe the syntax of pointers and show only simple examples of their use. I discuss pointers early and often. I describe their effective use in various contexts and show programming idioms in which they appear. I discuss related issues of program efficiency versus maintainability. Pointers are a thread that is woven throughout this book. Why are pointers so important? My belief is that pointers are what gives C its power. Pointers allow the C programmer to implement many tasks more efficiently than is possible in other languages, and to perform some tasks, such as accessing the hardware directly, that are impossible in other languages. A thorough knowledge of pointers, then, is a prerequisite to becoming a good C programmer.

However, the power of pointers comes with a price. You can cut wood faster with a chain saw than with a nail file, but the chain saw can injure you a lot more seriously, and more quickly. Pointers are like the chain saw. Used correctly, they can simplify the implementation of an algorithm as well as make it more efficient. Used incorrectly, they can be the cause of errors that exhibit subtle and confusing symptoms and are thus extremely difficult to find. An incomplete understanding of pointers is dangerous because it invariably leads to pain rather than pleasure. This book gives you the depth of knowledge in pointers that you need to avoid the pain. Why Learn C?

Why is the C language still so popular? Historically, industry has embraced C for a number of reasons. Among these are its efficiency; good C programs can be nearly as efficient as assembly language programs, but they are considerably easier to develop. C gives programmers more control over where data is stored and how it is initialized than many languages do. C's lack of "safety net" features also contributes to its efficiency, but increases the likelihood of errors. For example, subscripts to arrays and accesses through pointers are not checked for validity, which saves time but makes it much more important that these features be used correctly. If the language is used with discipline, the potential problems can be avoided.

Finally, C is the foundation upon which C++ is built. C++ provides a different view of program design and implementation than C. Nevertheless, a thorough knowledge of C skills and techniques, such as using pointers and the standard library, will also be useful for the C++ programmer. Who Should Use this Book?

There are two notable exceptions to this organization. The first is pointers, which are discussed in many different contexts throughout the book. The second is Chapter 1, which gives a quick introduction to the basics of the language. The introduction helps get you started writing simple programs quickly. The topics it presents are covered more thoroughly in subsequent chapters.

Designed for professionals and advanced students, Pointers on C provides a comprehensive resource for those needing in-depth coverage of the C programming language. An extensive explanation of pointer basics and a thorough exploration of their advanced features allows programmers to incorporate the power of pointers into their C programs. Complete coverage, detailed explanations of C programming idioms, and thorough discussion of advanced topics makes Pointers on C a valuable tutorial and reference for students and professionals alike.

They are important in C, because they allow us to manipulate the data in the computer's memory. This can reduce the code and improve the performance. If you are familiar with data structures like lists, trees and graphs, you should know that pointers are especially useful for implementing those. And sometimes you even have to use pointers, for example when working with files.

Pointers are widely used in C and C++. Essentially, they are variables that hold the memory address of another variable. For a refresher on pointers, you might consider checking out this overview on C Pointers.

Here, add_one(x) accesses the first element and increments its value by one. Using a list means that the end result appears to have modified the value. So pointers in Python do exist? Well, no. This is only possible because list is a mutable type. If you tried to use a tuple, you would get an error:

The above code demonstrates that tuple is immutable. Therefore, it does not support item assignment. list is not the only mutable type. Another common approach to mimicking pointers in Python is to use a dict.

Here, you can access func_calls and call inc_func_calls() in various places in your applications and simulate pointers in Python. This is useful when you have something like metrics that need to be used and updated frequently in various parts of your applications.

You now have a better understanding of the intersection between Python objects and pointers. Even though some of the distinctions between names and variables seem pedantic, fundamentally understanding these key terms expands your understanding of how Python handles variables.

In most cases, when you initialize a raw pointer or resource handle to point to an actual resource, pass the pointer to a smart pointer immediately. In modern C++, raw pointers are only used in small code blocks of limited scope, loops, or helper functions where performance is critical and there is no chance of confusion about ownership.

Smart pointers are designed to be as efficient as possible both in terms of memory and performance. For example, the only data member in unique_ptr is the encapsulated pointer. This means that unique_ptr is exactly the same size as that pointer, either four bytes or eight bytes. Accessing the encapsulated pointer by using the smart pointer overloaded * and -> operators is not significantly slower than accessing the raw pointers directly.

Smart pointers have their own member functions, which are accessed by using "dot" notation. For example, some C++ Standard Library smart pointers have a reset member function that releases ownership of the pointer. This is useful when you want to free the memory owned by the smart pointer before the smart pointer goes out of scope, as shown in the following example.

Smart pointers usually provide a way to access their raw pointer directly. C++ Standard Library smart pointers have a get member function for this purpose, and CComPtr has a public p class member. By providing direct access to the underlying pointer, you can use the smart pointer to manage memory in your own code and still pass the raw pointer to code that does not support smart pointers.

shared_ptrReference-counted smart pointer. Use when you want to assign one raw pointer to multiple owners, for example, when you return a copy of a pointer from a container but want to keep the original. The raw pointer is not deleted until all shared_ptr owners have gone out of scope or have otherwise given up ownership. The size is two pointers; one for the object and one for the shared control block that contains the reference count. Header file: . For more information, see How to: Create and Use shared_ptr Instances and shared_ptr Class.

When you work with COM objects, wrap the interface pointers in an appropriate smart pointer type. The Active Template Library (ATL) defines several smart pointers for various purposes. You can also use the _com_ptr_t smart pointer type, which the compiler uses when it creates wrapper classes from .tlb files. It's the best choice when you do not want to include the ATL header files.

In addition to smart pointers for COM objects, ATL also defines smart pointers, and collections of smart pointers, for plain old C++ objects (POCO). In classic Windows programming, these types are useful alternatives to the C++ Standard Library collections, especially when code portability is not required or when you do not want to mix the programming models of the C++ Standard Library and ATL. 041b061a72


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