In this lesson, we would learn about C++ pointers. This is one of the few topics that is distinguishes C++ from many other programming languages. So, it’s important you understand it.<\/p>\n
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Pointers in C++ are variables that store memory address of other variables. So if you have a variable x, then to get its memory address, you use &x. The code below displays address of three variables<\/p>\n
\/\/ Printing memory addresses of variables<\/span>\r\nint<\/span> main<\/span> () {\r\n \/\/ declare some variables<\/span>\r\n int<\/span> x =<\/span> 67<\/span>;\r\n string name =<\/span> \"Kindson\"<\/span>;\r\n double<\/span> y =<\/span> 54.32<\/span>;\r\n\r\n \/\/ print address of x<\/span>\r\n cout <<<\/span> \"Address of x: \"<\/span><<<\/span> &<\/span>x <<<\/span> endl;\r\n\r\n \/\/ print address of name<\/span>\r\n cout <<<\/span> \"Address of name: \"<\/span> <<<\/span> &<\/span>name <<<\/span> endl;\r\n\r\n \/\/ print address of y<\/span>\r\n cout <<<\/span> \"Address of y: \"<\/span> <<<\/span> &<\/span>y <<<\/span> endl;\r\n\r\n return<\/span> 0<\/span>;\r\n}\r\n<\/pre>\nThe output of the program is:<\/p>\n
Address of x: 0x62fe08\r\nAddress of name: 0x62fde0\r\nAddress of y: 0x62fdd8\r\n<\/pre>\nAs you can see, the addressed are shown in hexadecimal (begins with 0x)<\/p>\n
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2. Creating Pointers<\/strong><\/h4>\nSimilar to normal variables, you also need to declare a pointer before you can use it. However, pointer names are preceded by an asterisk(*). For example<\/p>\n
int<\/span> *<\/span>myPointer; \/\/pointer to int<\/span>\r\n\r\nint<\/span>*<\/span> myPointer; \/\/pointer to int<\/span>\r\n\r\nint<\/span>*<\/span> myPointer, myVar; \/\/a pointer and an int<\/span>\r\n<\/pre>\nThe three lines above are all valid ways to declare a pointer. The first and second lines declares a pointer myPointer<\/em> which is a pointer to an int variable. Third line declares a pointer myPointer<\/em> and a normal variable myVar<\/em>.<\/p>\n <\/p>\n
3. Using Pointers in C++<\/strong><\/h4>\nLet’s now create a pointer and assign the address of a variable to it.<\/p>\n
\/\/ Working with point<\/span>\r\nint<\/span> main<\/span> () {\r\n \/\/ declare a variables, x<\/span>\r\n\tint<\/span> x =<\/span> 34<\/span>;\r\n\r\n\t\/\/ declare a pointer px<\/span>\r\n\tint<\/span> *<\/span>px;\r\n\r\n\t\/\/ assign the pointer a value<\/span>\r\n\tpx =<\/span> &<\/span>x;\r\n\r\n\t\/\/ display the pointer value<\/span>\r\n\tcout<<<\/span>\"Variable x \"<\/span> <<<\/span> x <<<\/span> \" is stored at \"<\/span> <<<\/span> px;\r\n\r\n return<\/span> 0<\/span>;\r\n}\r\n<\/pre>\nThe output is:<\/p>\n
Variable x 34 is stored at 0x62fe14\r\n<\/pre>\nMoreover, if you have a pointer and you want to know what value is stored there, you just also use *. The code below would get the value stored in px.<\/p>\n
cout<<<\/span>\"Value stored in \"<\/span> <<<\/span> px <<<\/span> \" is \"<\/span> <<<\/span> *<\/span>px;\r\n<\/pre>\n <\/p>\n
4. Some Pointer Concepts<\/strong><\/h4>\nThere are a few concepts on pointers I would like to mention here finally.<\/p>\n
\n\n\nSN<\/th>\n Concept & Description<\/th>\n<\/tr>\n \n1<\/td>\n Null Pointers<\/strong>A null pointer is is a constant with a value of zero defined in several standard libraries.<\/td>\n<\/tr>\n\n2<\/td>\n Pointer Arithmetic<\/strong>Also, you can also perform arithmetic operations with pointers. The four arithmetic operators that you can use on pointers are: ++, –, +, –<\/td>\n<\/tr>\n\n3<\/td>\n Pointers vs Arrays<\/strong>There is a relationship between pointers and arrays. We’ll explore this in later lessons<\/td>\n<\/tr>\n\n4<\/td>\n Array Pointers<\/strong>You can define arrays to hold a number of pointers.<\/td>\n<\/tr>\n\n5<\/td>\n Pointer to Pointer<\/strong>C++ allows you to have pointer holding the memory address of another pointer.<\/td>\n<\/tr>\n\n6<\/td>\n Passing Pointers to Functions<\/strong>Passing arguments by reference or by address both allow for the passed argument to be modified in the calling function by the called function.<\/td>\n<\/tr>\n\n7<\/td>\n Returning Pointer from Functions<\/strong>You can also allows to function to return a pointer to local variable, static variable as well as\u00a0 dynamically allocated memory.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n