Interactive Systems Corporation (styled INTERACTIVE Systems Corporation, abbreviated ISC) was a US-based software company and the first vendor of the Unix operating system outside AT&T, operating from Santa Monica, CA. It was founded in 1977 by Peter G. Weiner, a RAND Corporation researcher who had previously founded the Yale University computer science department and had been the Ph. D. advisor to Brian Kernighan, one of Unix's developers at AT&T.