What is Pointers: Definition and 89 Discussions

In computer science, a pointer is an object in many programming languages that stores a memory address. This can be that of another value located in computer memory, or in some cases, that of memory-mapped computer hardware. A pointer references a location in memory, and obtaining the value stored at that location is known as dereferencing the pointer. As an analogy, a page number in a book's index could be considered a pointer to the corresponding page; dereferencing such a pointer would be done by flipping to the page with the given page number and reading the text found on that page. The actual format and content of a pointer variable is dependent on the underlying computer architecture.
Using pointers significantly improves performance for repetitive operations, like traversing iterable data structures (e.g. strings, lookup tables, control tables and tree structures). In particular, it is often much cheaper in time and space to copy and dereference pointers than it is to copy and access the data to which the pointers point.
Pointers are also used to hold the addresses of entry points for called subroutines in procedural programming and for run-time linking to dynamic link libraries (DLLs). In object-oriented programming, pointers to functions are used for binding methods, often using virtual method tables.
A pointer is a simple, more concrete implementation of the more abstract reference data type. Several languages, especially low-level languages, support some type of pointer, although some have more restrictions on their use than others. While "pointer" has been used to refer to references in general, it more properly applies to data structures whose interface explicitly allows the pointer to be manipulated (arithmetically via pointer arithmetic) as a memory address, as opposed to a magic cookie or capability which does not allow such. Because pointers allow both protected and unprotected access to memory addresses, there are risks associated with using them, particularly in the latter case. Primitive pointers are often stored in a format similar to an integer; however, attempting to dereference or "look up" such a pointer whose value is not a valid memory address will cause a program to crash. To alleviate this potential problem, as a matter of type safety, pointers are considered a separate type parameterized by the type of data they point to, even if the underlying representation is an integer. Other measures may also be taken (such as validation & bounds checking), to verify that the pointer variable contains a value that is both a valid memory address and within the numerical range that the processor is capable of addressing.

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  1. fluidistic

    Questions about C++, pointers, OS and compiler memory allocation

    Sorry I don't have the codes right now. In C plus plus, when I declare an int, but don't assign any value to it, a space in memory is allocated for it. I can define a pointer and check its adress in hexadecimal, so far so good. I can run this program over and over and usually the int is...
  2. shivajikobardan

    Comp Sci What happens in memory during DMA using pointers?

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  3. C

    AI Computation (self study analysis, pointers welcome)

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  4. C

    Comp Sci Creating 2D Arrays with Pointers in C | Efficient Memory Allocation

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  5. REEEEEEEE

    Need pointers on how to convert schematic to breadboard

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  6. evinda

    MHB Why do we use & before ptr->points?

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  7. Y

    Simple Question: Pointers and Uninitialized Variables Explained

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  8. Mark44

    C/C++ C++ swap routines: pointers vs. references

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  9. Y

    Please help with a problem displaying a string using pointers

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  10. pj96

    Help with Numerical Problem: Pointers Needed!

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  11. D

    What is the output of this C program with int pointers?

    Homework Statement I am supposed to analyze the code and find it's output without running it. Some things were unclear so i did run it and i have some things that puzzle me. Homework Equations 3. The Attempt at a Solution [/B] #include <stdio.h> #include <stdlib.h> #include <string.h> enum e...
  12. drgibbles

    Processor and Memory data alignment with base pointers?

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  13. doktorwho

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  14. M

    C/C++ Usefulness of Pointers in C++?

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  15. N

    MHB Fixing Code to Print "Print": Nodes and Pointers Programming Error

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  16. R

    Exercise on adding elements to a list

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  17. levadny

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    Dear Friends! My post about dinamic arrays. For example little bit code. // size int const X = 5; int const Y = 4; int const Z = 3; // one dimension array printf("\nOne dimension\n"); // array of pointers int * Arr; // create array Arr = new int [X]...
  18. Prof. 27

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  19. SnakeDoc

    Pointers -->(makes integer from pointer without cast)

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  20. SnakeDoc

    C Programming: Arrays and pointers

    Homework Statement So I created two arrays one called departure_time and the other arrival_time and populate each array as follows. I've tried both putting 8 and defining N as 8 int departure_times[N]={480, 538, 679, 767, 840, 945, 1140, 1305}; int arrival_times[N]={616, 712, 811, 900, 968...
  21. ChrisVer

    Pointers to const in func parameters

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  22. ChrisVer

    Question on pointers (ROOT TTree example)

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  23. cpscdave

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  24. I

    C/C++ C++ String Functions with Pointers

    Assign the first instance of The in movieTitle to movieResult. Sample program: #include <iostream> #include <cstring> using namespace std; int main() { char movieTitle[100] = "The Lion King"; char* movieResult = 0; <STUDENT CODE> cout << "Movie title contains The? "; if...
  25. I

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  26. G

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  27. J

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  28. B

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  29. C

    C allocating array of pointers

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  30. A

    Why Are Pointers Necessary in Programming?

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  31. A

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    Homework Statement Ok, I'm learning C programming and I'm trying to create a dynamic 2D array. This is the code that seems to work in creating a dyamic array. I found it in a book. //rows and cols are values entered by the user when the program runs. int **(matA) =...
  32. N

    Proofing Linear Algebra: Tips, Advice and Pointers

    I have done some "proofs" before in calculus. At this moment I am required to write proofs for linear algebra and I find them highly unintuitive and confusing -- I often don't know where to begin or what to do. Can you guys leave some pointers, tips, advice, etc. for how to prove things...
  33. O

    New to electrical engineering (begginer), need some pointers please :p

    Anyways, I will first start off by saying my name is Aaron Orszak and I live in Montreal, Quebec. Lately I've been really into things like computer programming (python and ruby mainly) but I sadly gave up on it because it just didnt fill the void. Right now I am really into electronics and want...
  34. Z

    [C] Stupid pointers what the heck is going on here

    Hi, I don't understand how this can be so difficult. So I have a [char ** ptr] pointer that stores a list of arguments. I'm able to PRINT each of them by doing printf("%s\n", ptr[i]) But how the heck do I is strcmp to see if a certain argument is there? Apparently I cannot just do [if...
  35. F

    Schools Pointers needed in getting into physics grad school

    I aspire to getting into a reputable US physics grad school. As I'm aware of so far (correct me if I'm wrong), there are 4 main things grad schools look at: (in no particular order) 1. Your GPA 2. Your research experience 3. Recommendation letters 4. Your physics GRE score Do any of...
  36. T

    Pascal's Triangle: Pointers and Dynamic Memory Allocation

    Here is the given problem. I have a question for part c and e. Calculate and print first 12 rows of the famous Pascal triangle, as shown below. Each number is the sum of the two numbers immediately above it. As our intent is to practice pointers, functions, loops, and dynamic memory...
  37. T

    Comp Sci C++ compare strings program using pointers

    Homework Statement Create a function called isEqual(). isEqual() takes two strings and determines if the strings are identical. isEqual (s1, s2) should be the same as s1 = = s2 #include "stdafx.h" #include <iostream> using namespace std; bool isEqual(int *s, int *st, int x); int...
  38. P

    C: 2D arrays with structs and pointers

    I wanted to make a variant on having a player just walking around a small 2d map. Instead of having 2 variables to store the current x and y values of the player position in a certain array, I want to make a 2d array that is filled with NULL pointers. Then the player would be represented as a...
  39. Y

    Simpel question in C (tcshell) about strings and pointers

    If I need to write a c program which get a string from the stdin and prints it after a certain manipulation, the program is called that way: echo "Hello, World. bla bla bla" | program <arg> How can I save the string in my program before working on it? Thanks in advance
  40. E

    Comp Sci Creating an Array of Pointers to Objects in C++ Without Using Virtual Functions

    Homework Statement suppose i have class A. now i have 2 derative classes: A_1, A_2. i would like to create a 4'th class: Array_Class. Array_Class will have 2 pointers array (one for each class - A_1, A_2). i want to be able to get an object pointer from class A_1 or A_2, and place it in...
  41. F

    How to properly use pointers and structs in C?

    Hello all, I am experiencing some odd output behavior from a program that I am working on: Header file #include <pthread.h> struct ringbuf_t { pthread_mutex_t mutex; pthread_cond_t cond_full; pthread_cond_t cond_empty; int bufsiz; int front; int back; char* buf...
  42. D

    Using pointers in a User Define Function

    Homework Statement There is a user defined function that looks like this: void DisplayMenu(char *item) My problem is that I have no clue on how I could include "*item" in my function, without changing the name or algorithm. The purpose of this function to to display the list of apps...
  43. A

    Comp Sci Fortran debugging help: faulty pointers?

    Hi, I tried compiling my program in Fortran using the following commands: nagfor -g90 -C=all -C=undefined -g -gline -nan -u -mtrace=all test09b.f90 cell_functions.o -o test09b I ended up getting this error message: [Allocated item 15285 (size 17) = Z'FFFFFFFFB744A790'] Runtime Error...
  44. T

    Green Laser Pointer Reflecting: Hot or Not?

    Hey guys, I'm wondering.. If I were to reflect a green laser pointer to the mirror, will the reflected laser be hot too? Or will I be heating the mirror?
  45. J

    C/C++ Queue made with pointers in C++, questions

    Can someone explain how the function queue::store(int i) (see attachment) works for a sequence of calls to it. Or give a reference to something or give a diagram, please. Doesn't each instant (i.e., each memory location) have its own head, tail and next pointers as well as as the data member...
  46. C

    Pointers for the solution of 2nd order DE with variable coefficient

    Hi, I am looking at the following 2nd order DE with variable coefficient: y''(x)-(1/x+7)y(x)=0 I would be grateful for any help in regard to methods which may be applied to such an equation. Many thanks in advance! C.
  47. J

    Scope problem when filling a vector of base class pointers.

    I'm trying to write a simple program to calculate the impedance of an AC circuit consisting of an arbitrary number of resistors, capacitors and inductors combined in series or parallel. First I ask the user to create the components they wish to use in the circuit, and this is where I hit the...
  48. J

    Research internship cv - any pointers?

    I've pretty much finished writing a CV which I intend to email to some prospective summer research placements at universities in London and possibly internationally. Some bits are nagging me though, for example: In the education section I've listed my previous year grades, and my expected...
  49. T

    Recommendations for Self-Study in Math and Physics for Engineering Students

    First of all, sorry for my bad english, it isn't my primary language. I'll try to describe the courses I have taken as best as I can, since the school system and courses names here might not be the same as everywhere else. I completed college-level Physics I, II and III courses. Physics 1 was...
  50. O

    Pointers for solving a sum

    Hi all, perhaps someone can shed some light on the following sum: \lim_{m\rightarrow\infty}\frac{1}{m}\sum_{k=1}^{m-1}\left[1-\left(\frac{k}{2m-k}\right)^{1/2} \right]^2 What particularly throws me off is having the m variable as part of the summands. I have ran numerical simulations...
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