as function arguments, but need a bit of in depth explanation as to understanding dynamic memory allocation, and how to know when they are allocated? It is because I am confused on how memory works whenever I use pointers or references or allocating memory in C++?
So, in C++ I understand using pointers and references in as function arguments, but need a bit of in depth explanation as to understanding dynamic memory allocation, and how to know when they are allocated?
It is because I am confused on how memory works whenever I use pointers or references or allocating memory in C++?
language, which allows programmers to directly manipulate memory to efficiently manage the memory - the most critical and scarce resource in computer - for best performance. However, "pointer" is also the most complex and difficult feature in C/C++ language.
Pointers are extremely powerful because they allows you to access addresses and manipulate their contents. But they are also extremely complex to handle. Using them correctly, they could greatly improve the efficiency and performance. On the other hand, using them incorrectly could lead to many problems, from un-readable and un-maintainable codes, to infamous bugs such as memory leaks and buffer overflow, which may expose your system to hacking. Many new languages (such as Java and C#) remove pointer from their syntax to avoid the pitfalls of pointers, by providing automatic memory management.
Although you can write C++ programs without using pointers, however, it is difficult not to mention pointer in teaching C++ language. Pointer is probably not meant for novices and dummies.
1. Pointer Variables
A computer memory location has an address and holds a content. The address is a numerical number (often expressed in hexadecimal), which is hard for programmers to use directly. Typically, each address location holds 8-bit (i.e., 1-byte) of data. It is entirely up to the programmer to interpret the meaning of the data, such as integer, real number, characters or strings.
To ease the burden of programming using numerical address and programmer-interpreted data, early programming languages (such as C) introduce the concept of variables. A variable is a named location that can store a value of a particular type. Instead of numerical addresses, names (or identifiers) are attached to certain addresses. Also, types (such as int, double, char) are associated with the contents for ease of interpretation of data.
Each address location typically hold 8-bit (i.e., 1-byte) of data. A 4-byte int value occupies 4 memory locations. A 32-bit system typically uses 32-bit addresses. To store a 32-bit address, 4 memory locations are required.
Pointer Variables (or Pointers)
A pointer variable (or pointer in short) is basically the same as the other variables, which can store a piece of data. Unlike normal variable which stores a value (such as an int, a double, a char), a pointer stores a memory address.
Declaring Pointers
Pointers must be declared before they can be used, just like a normal variable. The syntax of declaring a pointer is to place a * in front of the name. A pointer is associated with a type (such as int and double) too.
type *ptr; // Declare a pointer variable called ptr as a pointer of type // or type* ptr; // or type * ptr; // I shall adopt this convention
For example,
int * iPtr; // Declare a pointer variable called iPtr pointing to an int (an int pointer) // It contains an address. That address holds an int value. double * dPtr; // Declare a double pointer
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