What are dynamic arrays in Fortran?

Dynamic arrays

An array whose size is not defined at the compilation time but is defined at run time is known as a dynamic array.

For the declaration of this array, we use the keyword allocatable. These arrays are quite helpful to accurately use the required memory at the required time.

Syntax

Let’s discuss the basic syntax of dynamic arrays.

One-dimensional

type, dimension(: ), allocatable :: name

Two-dimensional

type, dimension(:,: ), allocatable :: name

n-dimensional

To create n-dimensional arrays, repeat : $n$ times in the dimension() method.

One-dimensional dynamic arrays

After defining the dimension of an array, we have to use the allocate() function to allocate the memory to the defined array.

Allocate(arr1(v1))

We can also use the deallocate() function to free the memory location.

Deallocate(arr1)

Two/n-dimensional dynamic arrays

To initialize a two-dimensional array, use the code below.

Integer, dimension ( : , : ), Allocatable :: arr2

To allocate the memory space:

Allocate(arr2(v1 , v2))

To deallocate:

Deallocate(arr2)

Code

The code snippet below demonstrates the use of dynamic arrays.