In the November 1980 Word Ways, I briefly described a computer program designed by Lawrence J. Mazlack to place letters one at a time in a specified crossword grid until all vertical and horizontal slots are filled by words in a stored dictionary. Even though his test grids were very simple (the largest one, a 13-by-13, contained 30 percent blank letters), the program did not always succeed in fully filling them with words. More dismayingly, Mazlack's program completely failed to find a double word square of size 4-by-4, although this may have been due to a limited vocabulary size (2000 words).
Eckler, A. Ross
"Crossword Construction by Computer,"
Word Ways: Vol. 14
, Article 6.
Available at: https://digitalcommons.butler.edu/wordways/vol14/iss3/6