But also had to be accessible to the scientific computing community whose primary language, with a design closely tied to serial architectures, was FORTRAN.
On the other hand, compared with other contemporary languages which were by design extensible (notably ALGOL-68), FORTRAN was less than well suited to this task.
The result was noticeably inelegant and did require a great deal of new learning.
Operationally, there was an overhead to transfer computational data into and out of the array, and problems which did not fit the 64x64 matrix imposed additional complexity to handle the boundaries (65x65 was perhaps the worst case!)
A later version of the DAP used Fortran-Plus instead which was based on FORTRAN 77 and had more flexible indexing.