Executive Routine). MASTER was a multi-tasking, disk-based OS but still batch job oriented. Card jobs were cached to disk and printer output spooled. MASTER optimized memory usage with page-mapping hardware. An operating system called REAL-TIME SCOPE existed for both lower- and upper-3000 systems. A disk-based version of SCOPE was eventually made available for the upper-3000 systems. FORTRAN, COBOL, and ALGOL were available. The assembly language was called COMPASS. These were available from CDC. An APL system for the upper 3000 series computers was developed at the University of Massachusetts Amherst. This system was made available to other users of the upper 3000 series. Character set The operating systems for the CDC 3xxx typically used six-bit characters, so the 64 character set did not contain lowercase letters. The character set contained (in display code order): : A-Z 0-9 + - * / ( ) $ = (space) , . # [ ] % " _ ! & ' ? < > @ \ ^ ; This six-bit extension of the four-bit BCD encoding was referred to as BCDIC (BCD interchange code.) IBM later extended this code further to create the eight-bit "extended BCDIC", or EBCDIC code. Depending on the device, some characters are rendered differently, especially the lineprinter and some terminals: Note the absence of control characters, especially carriage return and line feed. These were encoded by the record structure. Partial list of users United States Oregon State University offered a CDC 3300 for use from the mid-to-late 1960s up until about 1980. It used a home grown operating system known as OS3 (for Oregon State Open Shop Operating System). The U.S. Internal Revenue Service used CDC 3000 series computers for many years. Northeastern University in Boston used a CDC 3300 in the early 1970s. International Timesharing Corporation (ITS) of Chaska, Minnesota sold timesharing services using CDC 3300s. (ITS later acquired another timesharing company that used CDC 3600s, before it, in turn, was acquired by United Computing Systems of Kansas City, Missouri.) California State University at Northridge had a dual 3170 that provided timesharing service to the California State University and College system. Many of the other campuses also had CDC 3150 machines for local batch operation. In 1970 CDC 3150s were installed at most campuses of the California State College system. San Jose State and LA State got CDC 3300s and served as regional data centers with (very flaky) data