In the original specification of the Computer Sciences Corporation 1107 Monitor System, which was eventually adopted by Univac as EXEC II, the FIELDATA “Master Space” (octal 0) code was used in card input streams to distinguish command and data cards. In their manuals, CSC and later Univac used the “▽” character, an inverted Greek capital delta, to signify the Master Space. Noting the resemblance of this graphic to the Delta printed for character code 4 by the UNIVAC 1004 some sites, including Case Institute of Technology and Chi Corporation, swapped the printer codes so that CPU code 00 printed as “Δ” and code 04 as “@”. The card reader codes remained the same; a 7-8 punch in column 1 signified a “control card”.