How is a multidimensional array defined pointer, Computer Engineering

Assignment Help:

How is a multidimensional array defined in terms of a pointer to a collection of contiguous arrays of lower dimensionality ?

C does not have true multidimensional arrays. However, because of the generality of C's type system, you can have arrays of arrays.

Here is a two-dimensional array, although the techniques can be extended to three or more dimensions.

int a2[5][7];

Formally, a2 is an array of 5 elements, each of which is an array of 7 ints. Thus a two dimensional array, for example, is actually a collection of one dimensional arrays. Therefore, we can define a two-dimensional array as a pointer to a group of contiguous one dimensional arrays. A two dimensional array declaration can be written as

Int (*a2)[7];

We need parenthesis (*a2) since [] have a higher precedence than * So:

int (*a2)[7]; declares a pointer to an array of 7 ints.

int *a[7]; declares an array of 7 pointers to ints.

This concept can be generalized to higher dimensional arrays; that is

data - type (*variable name) [expression1][expression2].....[expression n];

If we don't know how many columns the array will have, we'll clearly allocate memory for each row (as many columns wide as we like) by calling malloc, and each row will therefore be represented by a pointer. To keep track of those pointers, we want to simulate an array of pointers, but we don't know how many rows there will be, either, so we'll have to simulate that array (of pointers) with another pointer, and this will be a pointer to a pointer.

This is best illustrated with an example:

#include

int **array;

array = malloc(nrows * sizeof(int *));

if(array == NULL)

{

fprintf(stderr, "out of memory\n");

exit or return

}

For (i = 0; i < nrows; i++)

{

array[i] = malloc(ncolumns * sizeof(int));

if(array[i] == NULL)

{

fprintf(stderr, "out of memory\n");

exit or return

}

 


Related Discussions:- How is a multidimensional array defined pointer

Define memory read and write operation, Define Memory read and write operat...

Define Memory read and write operation The transfer of information from a memory word to outside environment is known as read operation. The transfer of new information to be k

Prove, state and prove distributive law?

state and prove distributive law?

Human intelligence in culture - artificial intelligence, Human intelligence...

Human intelligence in culture: Understand human intelligence in culture  "AI" can be seen as just the latest tool in the philosopher's toolbox for answering questions about

Characteristics of the id process, The following is taken from the first ed...

The following is taken from the first edition of the Set Book. We have included this because we find these characteristics helpful. We will refer to them later. In addition to t

Use verilog function to define the width of a multi-bit port, Can I use a V...

Can I use a Verilog function to define the width of a multi-bit port, wire, or reg type? Width  elements  of  ports,  wire  or  reg  declarations  require  a  constant  in  bot

Global fon, GlobalFon is an international communication company, which offe...

GlobalFon is an international communication company, which offers international prepaid calling cards. They introduced three different types of cards, (1) AsiaFon: is cheapest for

Explain asynchronous decade counter, Draw the circuit diagram of Asynchrono...

Draw the circuit diagram of Asynchronous decade counter and explain its working. Ans: To  design  a  circuit diagram of decade  asynchronous  counter  initially  we  dr

Which layer is not present in TCP/IP model, Which Layer is not present in T...

Which Layer is not present in TCP/IP model? Presentation layer is not present into Transfer Control Protocol/IP Model.

#title.sequential circuit, design modulo 12 up synchronous counter using t ...

design modulo 12 up synchronous counter using t flip flop

Explain message switching, Explain Message switching. Recourse computer...

Explain Message switching. Recourse computer sends data to switching office that stores the data into buffer and seems for a free link. Sends link to other switching office, if

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd