The C programming language offers various features and functionalities to its users. And pointers are one of them. Pointers help programmers in better coding. With the help of a pointer, you can work with different memory addresses of different variables. It is one of the most powerful and useful features of the C programming language.<\/p>\n
Let me tell you about addresses in C before we start with pointers.<\/p>\n
Whenever a variable is defined then you can access the memory address of that variable. Suppose, you define a variable named var then if you use &var,<\/strong> it will give the variable var\u2019s address in memory. In C, you can get the memory address of a variable using &<\/strong> symbol.<\/p>\n Example of Address in C<\/strong><\/p>\n Output<\/strong><\/p>\n The main purpose of a pointer is to get the memory address of the variable which is defined in the program code. Pointers are special variables. It holds the memory address of another variable of the same data type. Without the help of a pointer, you cannot perform tasks such as dynamic memory allocation and many tasks in the C programming language.<\/p>\n Example of pointer in C<\/strong><\/p>\n We associate data type to a pointer because it knows how much bytes of data can it store.<\/p>\n Basic example of pointers in C<\/strong><\/p>\n Output:-<\/strong><\/p>\n In C, you can declare a pointer variable using *(asterisk)<\/strong> symbol.<\/p>\n Syntax:-<\/strong><\/p>\n In the above, we have declared a pointer p<\/strong> of type int<\/strong> and also declared a pointer c<\/strong> of type char.<\/strong><\/p>\n You can also declare a pointer variable like below:-<\/p>\n In the above, we have declared a pointer v1 and a normal variable v2.<\/p>\n Example of how to Declare a pointer in C<\/strong><\/p>\n Output<\/strong><\/p>\n TechVidvan Tutorial: Declare a pointer in C!<\/p>\n Value is: 10 In the above example, the address of the value is assigned to the pointer variable named point.<\/strong> And we have used *point<\/strong> to get the value that is stored in that address.<\/p>\n In C, we can also change the value pointed by the pointers easily.<\/p>\n Let\u2019s take the above example. From the above example, we can change the value of the integer variable val<\/strong> like below:-<\/p>\n Output:-<\/strong><\/p>\n TechVidvan Tutorial: Changing the value pointed by a pointer!<\/p>\n Value is: 9 See, we have changed the value of val<\/strong> variable from 10 to 9. And the memory address is also different.<\/p>\n In C, pointers have various useful concepts that a programmer must learn. Following are some important concepts in pointers:-<\/p>\n In a pointer, you can use four arithmetic operators such as ++, –, + and – on pointers. With the help of this, you can perform certain arithmetic operations on pointers.<\/p>\n In C, you can also increment a pointer. You can use an array which will help you increment the pointer easily.<\/p>\n Example of incrementing a pointer<\/strong><\/p>\n Output:-<\/strong><\/p>\n TechVidvan Tutorial: Incrementing a pointer!<\/p>\n Value of value_array[0] = 141 Value of value_array[1] = 1 The C programming language also has the functionality to decrement a pointer.<\/p>\n Example of Decrementing a C pointer<\/strong><\/p>\n Output:-<\/strong><\/p>\n TechVidvan Tutorial: Decrementing a pointer!<\/p>\n Value of value_array[1] = 1032 Value of value_array[0] = 141 You can also compare pointers by using relational operators like ==, <, and >.<\/p>\n Example of C Pointer Comparison<\/strong><\/p>\n Output:-<\/strong><\/p>\n TechVidvan Tutorial: Pointer Comparison!<\/p>\n Value of value_array[0] = 141 Value of value_array[1] = 1032 In the above example, we are incrementing the pointer variable until the address which the pointer points to is less than or equal to the address of the last element of the array.<\/p>\n In C, we can use an array of pointers to make your coding simple and easy.<\/p>\n For Example:-<\/strong><\/p>\n In the above example, we have declared point<\/strong> as an array of 4 integer pointers. And each element in the point variable holds a pointer to an integer value.<\/p>\n Example ofArray of pointers in C<\/strong><\/p>\n Output:-<\/strong><\/p>\n TechVidvan Tutorial: Array of pointers!<\/p>\n Value => var[0]: 42 In the above example, we used an array of integers but you can use an array of characters also.<\/p>\n Pointer to pointer is known as a chain of pointers. It means that the first pointer contains the address of the second pointer and it points to the location of actual value.<\/p>\n Syntax:-<\/strong><\/p>\n In the above example, we declared a pointer to pointer of type integer.<\/p>\n Example of Pointer to pointer<\/strong><\/p>\n Output:-<\/strong><\/p>\n You can also pass a pointer to a function. You can just simply declare the function parameter as a pointer type.<\/p>\n Example of Passing pointers to function<\/strong><\/p>\n Output:-<\/strong><\/p>\n TechVidvan Tutorial: Passing pointers to function!<\/p>\n Value is: 1002<\/p>\n<\/div>\n In C, you have seen that you can return an array from a function. In a similar way, you can also return a pointer from a function.<\/p>\n NOTE:-<\/strong> If you try to return the address of a local variable outside the function then the local variables of the function will go out of scope. And your program will never get executed.<\/p>\n So to avoid this type of error, you have to define the local variable as a static variable.<\/p>\n Example:- Return a pointer from a function<\/strong><\/p>\n Output:-<\/strong><\/p>\n TechVidvan Tutorial: Returning pointer from a function!<\/p>\n Address is: 0x601048 A pointer is known as a invalid pointer when it does not point to valid elements. You can also state that Uninitialized pointers are also known as invalid pointers.<\/p>\n In the above example, *a<\/strong> pointer is uninitialized so it is an invalid pointer. And the pointer variable point is exceeding the limit of array ar.<\/strong> So, it is also an invalid pointer.<\/p>\n A pointer that points to nowhere then it is known as null pointers. There are two methods to assign a null pointer:-<\/p>\n As you have seen, you can use an array to structure. Similarly, you can use a pointer to the structure. If you use pointers to a structure then you will have to use -> operator to access the members of the structure.<\/p>\n Example of structure pointer in C<\/strong><\/p>\n Output:-<\/strong><\/p>\n TechVidvan Tutorial: Pointer to structures!<\/p>\n First value is: 3 There are many uses of pointers in C programming.<\/p>\n You must know that there are some complex pointers available in C. Below is a table of the precedence and associativity of the operators which are used regarding pointers.<\/p>\n Before starting to read a pointer, you have to check that if () and []<\/strong> have the equal precedence. And also look for the associativity.<\/p>\n Example:-<\/strong><\/p>\n In the above example, you will notice that the associativity is left to right. In that case, the priority goes to (). Inside the bracket, you will notice that *(pointer operator)<\/strong> and point(Identifier)<\/strong> have the same precedence. So, the associativity will go right to left. First priority goes to point<\/strong> and second priority goes to *. At last, you can say that point is a pointer to an array of integers of size 2.<\/p>\n From the above tutorial, we learnt about pointers. We also discussed some important topics and concepts such as Address in C, Pointer to Pointer, Array to pointer, Passing pointer to a function, Applications of pointer etc. Programmers will gain various benefits by using pointers in C.<\/p>\n","protected":false},"excerpt":{"rendered":" The C programming language offers various features and functionalities to its users. And pointers are one of them. Pointers help programmers in better coding. With the help of a pointer, you can work with...<\/p>\n","protected":false},"author":1,"featured_media":82875,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[3510],"tags":[3779,3780,3781],"class_list":["post-81822","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-c-programming","tag-declare-pointer-in-c","tag-null-pointer-in-c","tag-pointers-in-c"],"yoast_head":"\n#include<stdio.h>\n\nint main()\n{\n int var = 2;\n printf(\"Value is: %d\\n\", var);\n printf(\"Memory address is: %p\\n\", &var);\n}\n<\/pre>\n
\nMemory address is: 0x7ffcd857e2dc<\/div>\nWhat is a pointer in C?<\/h3>\n
int a=5;\nint* point = &a; \/\/ pointer variable point is pointing to the address of the integer variable a!\n<\/pre>\n
How to use pointers in C?<\/h3>\n
\n
#include <stdio.h>\nvoid TechVidvan()\n{\n int var = 25;\n int *pt;\n pt = &var; \n printf(\"Address is: %p \\n\",pt);\n printf(\"Value is: %d \\n\", *pt);\t \n}\nint main()\n{\n TechVidvan();\n}\n<\/pre>\n
\nValue is: 25<\/div>\nDeclare a pointer in C<\/h3>\n
int* p;\nchar* c;<\/pre>\n
int* v1,v2;\n<\/pre>\n
#include<stdio.h>\n\nint main()\n{\n int val = 10;\n int* point;\n point = &val;\n printf(\"TechVidvan Tutorial: Declare a pointer in C!\\n\\n\");\n printf(\"Value is: %d\\n\", *point);\n printf(\"Memory address is: %p\\n\", point);\n}\n<\/pre>\n
\nMemory address is: 0x7ffdcf71bb14<\/p>\n<\/div>\nChanging the value in C pointers<\/h3>\n
#include<stdio.h>\n\nint main()\n{\n int val = 10;\n int* point;\n point = &val;\n val = 9;\n printf(\"TechVidvan Tutorial: Changing the value pointed by a pointer!\\n\\n\");\n printf(\"Value is: %d\\n\", *point);\n printf(\"Memory address is: %p\\n\", point);\n}<\/pre>\n
\nMemory address is: 0x7ffc167b00a4<\/p>\n<\/div>\nMore About C Pointers<\/h3>\n
Pointer Arithmetic Operators<\/h4>\n
Incrementing a pointer<\/h4>\n
#include <stdio.h>\nint main () {\n int value_array[] = {141, 1};\n int *point;\n point = value_array;\n for (int a = 0; a < 2; a++) {\n printf(\"TechVidvan Tutorial: Incrementing a pointer!\\n\\n\");\n printf(\"Value of value_array[%d] = %d\\n\", a, *point);\n printf(\"Address of value_array[%d] = %p\\n\", a, point);\n point++; \/\/ incrementing the pointer variable!\n }\n return 0;\n}\n<\/pre>\n
\nAddress of value_array[0] = 0x7ffe22d0679c
\nTechVidvan Tutorial: Incrementing a pointer!<\/p>\n
\nAddress of value_array[1] = 0x7ffe22d067a0<\/p>\n<\/div>\nDecrementing a pointer in C<\/h4>\n
#include <stdio.h>\nint main () {\n int value_array[] = {141, 1032};\n int *point;\n int max=2;\n point = &value_array[max-1];\n for (int a = max; a > 0; a--) {\n printf(\"TechVidvan Tutorial: Decrementing a pointer!\\n\\n\");\n printf(\"Value of value_array[%d] = %d\\n\", a-1, *point);\n printf(\"Address of value_array[%d] = %p\\n\", a-1, point);\n point--; \/\/ decrementing the pointer variable!\n }\n return 0;\n}<\/pre>\n
\nAddress of value_array[1] = 0x7ffeafc6efac
\nTechVidvan Tutorial: Decrementing a pointer!<\/p>\n
\nAddress of value_array[0] = 0x7ffeafc6efa8<\/p>\n<\/div>\nPointer Comparison in C<\/h4>\n
#include <stdio.h>\nint main () {\n int value_array[] = {141, 1032};\n int *point;\n int max=2;\n int a=0;\n point = value_array;\n while(point <= &value_array[max-1]) {\n printf(\"TechVidvan Tutorial: Pointer Comparison!\\n\\n\");\n printf(\"Value of value_array[%d] = %d\\n\", a, *point);\n printf(\"Address of value_array[%d] = %p\\n\", a, point);\n point++;\n a++;\n }\n return 0;\n}<\/pre>\n
\nAddress of value_array[0] = 0x7fff9f245d68
\nTechVidvan Tutorial: Pointer Comparison!<\/p>\n
\nAddress of value_array[1] = 0x7fff9f245d6c<\/p>\n<\/div>\nArray of Pointers in C<\/h4>\n
int *point[4];<\/pre>\n
#include <stdio.h>\nint main () {\n\n int value_array[] = {42, 366, 458, 112};\n int a, *point[4];\n printf(\"TechVidvan Tutorial: Array of pointers!\\n\\n\");\n \n for (a = 0; a < 4; a++) {\n \tpoint[a] = &value_array[a]; \/\/ assigning address!\n }\n for (a= 0; a < 4; a++) {\n \tprintf(\"Value => var[%d]: %d\\n\", a, *point[a] );\n }\n \n return 0;\n}\n<\/pre>\n
\nValue => var[1]: 366
\nValue => var[2]: 458
\nValue => var[3]: 112<\/p>\n<\/div>\nPointer to Pointer in C<\/h4>\n
int **point;<\/pre>\n
#include <stdio.h>\nint main () {\n int val;\n int *pt;\n int **point;\n\n val = 55;\n pt = &val;\n point = &pt;\n printf(\"Value => val: %d\\n\", val);\n printf(\"Value => *pt: %d\\n\", *pt );\n printf(\"Value => **pptr: %d\\n\", **point);\n return 0;\n}<\/pre>\n
\nValue => *pt: 55
\nValue => **pptr: 55<\/div>\nPassing pointers to function in C<\/h4>\n
#include <stdio.h>\nvoid display(int *val);\nint main () {\n\n int a;\n display(&a);\n printf(\"TechVidvan Tutorial: Passing pointers to function!\\n\\n\");\n printf(\"Value is: %d\\n\",a);\n return 0;\n}\n\nvoid display(int *val) {\n *val = 1002;\n return;\n}<\/pre>\nReturn pointers from function in C<\/h4>\n
#include <stdio.h>\nint* printToscreen()\n{\n static int val = 2364; \/\/ defining the local variable as static to avoid execution error!\n return (&val); \/\/ function returning pointer!\n}\nint main()\n{\n int* point;\n point = printToscreen();\n printf(\"TechVidvan Tutorial: Returning pointer from a function!\\n\\n\");\n printf(\"Address is: %p\\n\", point);\n printf(\"Value is: %d\\n\", *point);\n return 0;\n}<\/pre>\n
\nValue is: 2364<\/p>\n<\/div>\nInvalid Pointers in C<\/h4>\n
int *a;\nint ar[10];\nint *point = ar+20;<\/pre>\n
Null Pointers in C<\/h4>\n
int *point1 = 0;\nint *point2 = NULL;<\/pre>\n
Benefits of using pointers in C<\/h4>\n
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Pointer to Structure in C<\/h4>\n
#include<stdio.h>\nstruct point\n{\n int a;\n float b;\n};\nint main()\n{\n struct point p1={3,6.3};\n struct point *p2=&p1;\n printf(\"TechVidvan Tutorial: Pointer to structures!\\n\\n\");\n printf(\"First value is: %d\\n\",p2->a);\n printf(\"Second value is: %0.1f\",p2->b);\n return 0;\n}<\/pre>\n
\nSecond value is: 6.3<\/p>\n<\/div>\nUsage of Pointers in C<\/h4>\n
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Complex Pointers in C<\/h4>\n
\n\n
\n Operator<\/strong><\/td>\n Precedence<\/strong><\/td>\n Associativity<\/strong><\/td>\n<\/tr>\n \n (), []<\/span><\/td>\n 1<\/span><\/td>\n Left to Right<\/span><\/td>\n<\/tr>\n \n *, identifier\u00a0<\/span><\/td>\n 2<\/span><\/td>\n Right to Left<\/span><\/td>\n<\/tr>\n \n Data Type<\/span><\/td>\n 3<\/span><\/td>\n _<\/span><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n \n
Read the pointer in C<\/h4>\n
int (*point)[2]<\/pre>\n
Summary<\/h3>\n