# C array index calculation

Write a C program to read elements in an array and find the sum of array elements. C program to find sum of elements of the array. How to add elements of an array using for loop in C programming. Logic to find sum of array elements in C programming. Basic Input OutputFor loopArray. Finding sum of array elements is easy when you know how to iterate through array elements.

In this post I will explain two approaches to find sum of array elements. First let us begin with the easiest approach.

Note: You can also re-write this program using a shorter and efficient approach using single for loop as written below. Read more - Program to find sum of array elements using recursion. You could use any of them. Learn more about shorthand operators in C programming. Recommended posts Array and matrix programming exercises index. C program to find sum of all even numbers between 1 to n. C program to find sum of all odd numbers between 1 to n. C program to find sum of all Prime numbers between 1 to n.

C program to find maximum and minimum elements in an array. C program to insert an element in array at specified position. Have a doubtwrite here. I will help my best.By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service.

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## Two Dimensional Arrays in C++ with Assignment

Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. Then I have drawn the matrix as a table, and filled the cells with numbers, each number being incremented from left to right, top to bottom. If I have, say, indexes 3 column and 4 row into the matrix, I know that it corresponds to the element at position 35 in the array, as it can be seen in the table that I've drawn. I believe there is some sort of formula to translate the 2 indexes of the matrix into a single index of the array, but I can't figure out what it is.

The way most languages store multi-dimensional arrays is by doing a conversion like the following:. If matrix has size, n by m [i. So its just like a number system of base 'n'. Note that the size of the last dimension doesn't matter.

For a conceptual understanding, think of a 3x5 matrix with 'i' as the row number, and 'j' as the column number. For 'row-major' ordering like thisthe layout looks like:. As you move along the row i.

Learn more. Ask Question. Asked 7 years, 3 months ago. Active 1 year, 5 months ago. Viewed 50k times. I have an 8x8 matrix, like this: char matrix[8][8]; Also, I have an array of 64 elements, like this: char array[64]; Then I have drawn the matrix as a table, and filled the cells with numbers, each number being incremented from left to right, top to bottom.

Any ideas?In computer sciencean array data structureor simply an arrayis a data structure consisting of a collection of elements values or variableseach identified by at least one array index or key. An array is stored such that the position of each element can be computed from its index tuple by a mathematical formula.

For example, an array of 10 bit 4 bytes integer variables, with indices 0 through 9, may be stored as 10 words at memory addresses,The memory address of the first element of an array is called first address, foundation address, or base address. Because the mathematical concept of a matrix can be represented as a two-dimensional grid, two-dimensional arrays are also sometimes called matrices.

In some cases the term "vector" is used in computing to refer to an array, although tuples rather than vectors are the more mathematically correct equivalent. Tables are often implemented in the form of arrays, especially lookup tables ; the word table is sometimes used as a synonym of array. Arrays are among the oldest and most important data structures, and are used by almost every program. They are also used to implement many other data structures, such as lists and strings.

They effectively exploit the addressing logic of computers. In most modern computers and many external storage devices, the memory is a one-dimensional array of words, whose indices are their addresses.

Processorsespecially vector processorsare often optimized for array operations. Arrays are useful mostly because the element indices can be computed at run time. Among other things, this feature allows a single iterative statement to process arbitrarily many elements of an array. For that reason, the elements of an array data structure are required to have the same size and should use the same data representation.

The set of valid index tuples and the addresses of the elements and hence the element addressing formula are usually, [3] [5] but not always, [2] fixed while the array is in use. The term array is often used to mean array data typea kind of data type provided by most high-level programming languages that consists of a collection of values or variables that can be selected by one or more indices computed at run-time.

Array types are often implemented by array structures; however, in some languages they may be implemented by hash tableslinked listssearch treesor other data structures. The term is also used, especially in the description of algorithmsto mean associative array or "abstract array", a theoretical computer science model an abstract data type or ADT intended to capture the essential properties of arrays.

The first digital computers used machine-language programming to set up and access array structures for data tables, vector and matrix computations, and for many other purposes. John von Neumann wrote the first array-sorting program merge sort induring the building of the first stored-program computer.

Some mainframes designed in the s, such as the Burroughs B and its successors, used memory segmentation to perform index-bounds checking in hardware. Assembly languages generally have no special support for arrays, other than what the machine itself provides.

Arrays are used to implement mathematical vectors and matricesas well as other kinds of rectangular tables. Many databasessmall and large, consist of or include one-dimensional arrays whose elements are records. Arrays are used to implement other data structures, such as lists, heapshash tablesdequesqueuesstacksstringsand VLists. Array-based implementations of other data structures are frequently simple and space-efficient implicit data structuresrequiring little space overheadbut may have poor space complexity, particularly when modified, compared to tree-based data structures compare a sorted array to a search tree.

One or more large arrays are sometimes used to emulate in-program dynamic memory allocationparticularly memory pool allocation. Historically, this has sometimes been the only way to allocate "dynamic memory" portably.An array is called circular if we consider first element as next of last element.

Circular arrays are used to implement queue Refer this and this. Given a name, we need to print all n people in order starting from given name. For example for 6 people, we create below auxiliary array. Now for any given index, we simply print n elements starting from it. For example, we print following 6. Below is the implementation of the above approach. An efficient solution is to deal with circular arrays using the same array. Recent articles on circular array.

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See your article appearing on the GeeksforGeeks main page and help other Geeks. Please Improve this article if you find anything incorrect by clicking on the "Improve Article" button below. Writing code in comment? Please use ide. Python3 program to demonstrate use of. Create an auxiliary array of twice size. Copy a[] to b[] two times. Python3 program to demonstrate the use of. Check out this Author's contributed articles. Improved By : Sam Load Comments.We have already discussed that whenever an array is declared in the program, contiguous memory to it elements are allocated.

Initial address of the array — address of the first element of the array is called base address of the array. Each element will occupy the memory space required to accommodate the values for its type, i. Next successive memory address is allocated to the next element in the array. This process of allocating memory goes on till the number of element in the array gets over.

Below diagram shows how memory is allocated to an integer array of N elements. Its base address — address of its first element is Since it is an integer array, each of its element will occupy 4 bytes of space.

Hence first element occupies memory from to Second element of the array occupies immediate next memory address in the memory, i. Hence it occupies from to In this way all the N elements of the array occupies the memory space.

If the array is a character array, then its elements will occupy 1 byte of memory each. If it is a float array then its elements will occupy 8 bytes of memory each.

## How do I find the length of an array in C/C++?

But this is not the total size or memory allocated for the array. They are the sizes of individual elements in the array. If we need to know the total size of the array, then we need to multiply the number of elements with the size of individual element. In the case of multidimensional array, we have elements in the form of rows and columns. Here also memories allocated to the array are contiguous.

But the elements assigned to the memory location depend on the two different methods:. Let us consider a two dimensional array to explain how row major order way of storing elements works.

In the case of 2D array, its elements are considered as rows and columns of a table. When we represent an array as intArr[i][j], the first index of it represents the row elements and the next index represents the column elements of each row.

When we store the array elements in row major order, first we will store the elements of first row followed by second row and so on. Hence in the memory we can find the elements of first row followed by second row and so on.

In memory there will not be any separation between the rows. We have to code in such a way that we have to count the number of elements in each row depending on its column index.

But in memory all the rows and their columns will be contiguous.When any integer ends in 0,2,4,6,8 and it can be divided by two with the remainder of zero, it is called as an even number. When any integer ends in 0,1,3,5,7,9 and it cannot be divided without a remainder, it is called as an odd number. This program allows the user to choose any value for array length and input values into the array.

Cpp program to check whether a number is even or odd. Cpp program to separate even and odd number from an array. Cpp program to display even and odd numbers from 1 to n. Cpp program find greatest of three numbers using function. Display odd and even numbers without if statements.

Your email address will not be published. Notify me of follow-up comments by email. Notify me of new posts by email. Separate odd and even number in a list to different two list. Calculate average of odd and even numbers in Java.

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**Calculate size of array for random indexing**

Me and some peers are working on a game Rigs ofRods and are trying to integrate OpenCL for physics calculation. At the same time we are trying to do some much needed cleanup of our data structures.

I guess I should say we are trying to cleanup our data structures and be mindful of OpenCL requirements. One of the problems with using open CL is the inability to use pointers as the memory space is different.

From what little I know of OpenCL is copies all the data onto the GPU then performs the calculations, pointer values would be copied but the address would not correspond to the expected address. The data in question is centralized in an array, when objects need to that data they use pointers to the object it needs, or stores an array index.

One solution to account for OpenCL is to use array index instead of pointers. This leads to hard coupling that could lead to headaches later on. As a solution I had the idea of calculating the array index based on the address of the start and the address of the current.

This of course would only work with a continuous array. I wrote a sample app to test this and it worked just fine, some people verified it on different platforms as well. I'm concerned that this more of a kludge than a bonified solution. I'm aware that this would not work no non-coninuous memory. How would you be able to tell it was continuous? What approaches have people used when dealing with this type of issue?

Although simple subtraction of pointers works, it's advisable to use std::distance. This will also work for iterator types that aren't pointers, and can be overloaded for custom types, too. Learn more. Asked 10 years, 6 months ago. Active 2 years, 9 months ago. Viewed 6k times.

Thanks, and my appologies if the formating is off, this is my first time posting a question. Apeiron Apeiron 7 7 silver badges 10 10 bronze badges. Active Oldest Votes. This should give you the index of pointer relative to base : pointer - base Yes, it's that easy.