What is meant by single array?

Answer 1

A single dimensional array, or one-dimensional array, is a contiguous block of memory that contains one or more elements, each of which can store a single fixed-width value. Since each element is the same length (in bytes), the total memory consumed by the array is equal to the product of the element length and the total number of elements.

One-dimensional arrays can be thought of as being a single row or column of numbered pigeon holes (the elements), such that each hole may contain a single object (a value). The numbers identifying each element are a zero-based incremental subscript, or index number. Thus for an array of n elements, the indexes will be in the range 0 to n-1. Some languages permit the first index to be offset from 0 such that the indexes will be in the range offset to offset+n-1, however this does not alter the actual index which is always zero-based.

Arrays permit random, constant-time access to any element in the array via the element's index. When accessing an element, the return value is a reference to the first memory address of that element. This is achieved through simple pointer arithmetic, such that element i will be found at memory address (i-1) x (size of element) bytes from the start address of the array (hence the index is always zero-based, regardless of any offset that is applied).

The value's stored in the elements must be of the same intrinsic type, but can be variables or constants of any kind, including object references and pointer variables, even pointers to other arrays.

Multi-dimensional arrays are merely an extension of one-dimensional arrays, such that each element contains a reference to another one-dimensional array (each element of which may refer to yet another one-dimensional array, and so on). For instance, a two-dimensional array can be thought of as being pigeon holes arranged in rows and columns, such that every row has the same number of columns, and every column has the same number of rows. A three-dimensional array can be thought of as being a cuboid of pigeon holes. Although it's difficult to imagine a four-dimensional array in a three-dimensional space, the easiest way to think of it is as being a one-dimensional array where each element contains a three-dimensional array. More simply, a series of cuboids arranged in a row or a column.

Multi-dimensional arrays needn't reside in contiguous memory, however each individual one-dimensional array that makes up a multi-dimensional array must itself reside in contiguous memory.

Accessing the individual elements of a multi-dimensional array requires one subscript per dimension. Thus for a cuboid that has 3 rows, 3 columns and 3 tiers, the middle box will be found at zero-based index (1, 1, 1). Again, simple pointer arithmetic is employed to determine the address of the element offset from the starting address of each one-dimensional array.

Answer 2

Maybe an oxymoron, for an array is an assembly or a group.

Can have meaning in radio astronomy, spreadsheets, and graphic layout in general.