fortran allocatable

Fortran `allocatable` is a feature that allows programmers to dynamically allocate memory for arrays, without having to specify the size at compile time. This makes it easier to write more flexible and efficient code, since the size of the array can be determined at run time based on the needs of the program.

To use `allocatable` arrays in Fortran, you must declare the array as `allocatable` using the `allocate` statement. For example:

real, allocatable :: my_array(:,:)

allocate(my_array(100,100))

This declares a two-dimensional `real` array called `my_array` that can be dynamically allocated with the `allocate` statement. In this case, we allocate the array to have 100 rows and 100 columns.

Once the array has been allocated, you can use it like any other Fortran array. When you are finished with the array, you should deallocate it using the `deallocate` statement:

deallocate(my_array)

This frees up the memory that was allocated for the array, allowing it to be used for other purposes.