Remote Spooling Communications Subsystem or RSCS is a subsystem ("virtual machine" in VM terminology) of IBM's VM/370 operating system which accepts files transmitted to it from local or remote system and users and transmits them to destination local or remote users and systems. RSCS also transmits commands and messages among users and systems.
RSCS is the software that powered the world’s largest network (or network of networks) prior to the Internet and directly influenced both internet development and user acceptance of networking between independently managed organizations. RSCS was developed by Edson Hendricks and T.C. Hartmann. Both as an IBM product and as an IBM internal network, it later became known as VNET. The network interfaces continued to be called the RSCS compatible protocols and were used to interconnect with IBM systems other than VM systems (typically MVS) and non-IBM computers.
The history of this program, and its influence on IBM and the IBM user community, is described in contemporaneous accounts and interviews by Melinda Varian. Technical goals and innovations are described by Creasy and by Hendricks and Hartmann in seminal papers. Among academic users, the same software was employed by BITNET and related networks worldwide.