How to use SSH for secure connections in macOS

The Secure Shell — SSH — allows you to send secure, encrypted, communications between computers that is nearly impossible to crack. Here's how to use it in terminals in computer labs which were attached to mainframe computers. Each user sat at a dumb terminal which was merely a display and keyboard connected to the mainframe computer. Later, as mini computers began to arrive, terminals were connected via a network.Originally, to access another computer on a network remotely a program called