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Programming languages or their standard libraries that support multi-dimensional arrays typically have a native row-major or column-major storage order for these arrays. Row-major order is used in C/C++/Objective-C (for C-style arrays), PL/I, [4] Pascal, [5] Speakeasy, [citation needed] and SAS. [6]
Illustration of row- and column-major order. Matrix representation is a method used by a computer language to store column-vector matrices of more than one dimension in memory. Fortran and C use different schemes for their native arrays. Fortran uses "Column Major" , in which all the elements for a given column are stored contiguously in memory.
Thus, if a two-dimensional array has rows and columns indexed from 1 to 10 and 1 to 20, respectively, then replacing B by B + c 1 − 3c 2 will cause them to be renumbered from 0 through 9 and 4 through 23, respectively. Taking advantage of this feature, some languages (like FORTRAN 77) specify that array indices begin at 1, as in mathematical ...
where c 1, c 2, ..., c n are scalars. The set of all possible linear combinations of v 1, ..., v n is called the column space of A. That is, the column space of A is the span of the vectors v 1, ..., v n. Any linear combination of the column vectors of a matrix A can be written as the product of A with a column vector:
On the other hand, FORTRAN programs store array elements from the same column together (a[1,1], a[2,1], a[3,1]), using column-major. Thus the order of two iteration variables in the first example is suitable for a C program while the second example is better for FORTRAN. [ 1 ]
The transpose (indicated by T) of any row vector is a column vector, and the transpose of any column vector is a row vector: […] = [] and [] = […]. The set of all row vectors with n entries in a given field (such as the real numbers ) forms an n -dimensional vector space ; similarly, the set of all column vectors with m entries forms an m ...
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The three important reasons for knowing whether a particular computer language compiler are row-major or column major: 1. most common is that the graphics adapter memory order has to be matched to main memory array order, or, at the least, performance suffers because the the data has to move just one cell (oe even pixel) at time if mismatched, otherwise large block moves can work.