COBOL, and other PLs of that day, were heavily integrated with the ISAM file structure. ISAM a precursor of SQL, and was basically a hash table implemented very

COBOL, and other PLs of that day, were heavily integrated with the ISAM file structure. ISAM a precursor of SQL, and was basically a hash table implemented very efficiently in a file. If you have hash tables, you can do pretty much anything. (Actually, it was better than a hash table. Once you had indexed (I) into the file, you could sequentially read forward (S). The AM is Access Method.)