Article snapshot taken from Wikipedia with creative commons attribution-sharealike license.
Give it a read and then ask your questions in the chat.
We can research this topic together.
Rochkind, Marc. βThe source code control system (SCCS).β IEEE Transactions on Software Engineering 1, no. 4 (1975).
"An extensible virtual toolkit (XVT) for portable GUI applications," Compcon Spring '92. Thirty-Seventh IEEE Computer Society International Conference, https://ieeexplore.ieee.org/document/186760