Arlet wrote:
whartung wrote:
Several terminals had multiple pages that they could use, upon which the computer could paint forms. Then the computer could readily, and instantly, switch from form to form. Also these forms used the concept of "protected fields" that the terminal would know how to navigate. This kept basic editing and navigation a completely local process until the user hits a "send" button that sends the entire form, all at once, to the host. Obviously, this really lowered the interactive load on a host computer, but at the same time it offered a "less friendly" user experience (things like dynamic field validation beyond simple contents, field lookup, dynamic pickers, etc.).
Environments like Thoroughbred BASIC and BBx addressed that problem with terminal driver tables that mapped program display control commands (called "mnemonics") to the escape sequences needed to produce the desired terminal operation. For example, PRINT 'CS', would cause the interpreter to emit an escape sequence to the terminal that would cause it to clear the screen and home the cursor. Similarly, PRINT 'CF', would result in only foreground fields being cleared, not the entire screen (eliminating the need to repaint the screen template after each enter/edit sequence). These environments operated in conversational mode, not the block mode described by whartung, and performed well, even on small, low-powered machines.
