BREAK - break handling in FRED.

The effect of pressing the BREAK or ATTN key while working in FRED depends on the situation.

Pressing BREAK while in input mode deletes everything typed in since the last carriage return. FRED prints a ? and then returns to command mode. "." points to the last line typed in.

Pressing BREAK while waiting in a \ command will terminate the wait.

Pressing BREAK (or typing anything other than a new-line character) while output is being listed to the terminal cuts off the output. A ? is printed and FRED returns to command mode.

Pressing BREAK while a UE command is executing is more complicated. The first time BREAK is pressed, the BREAK is recognized and remembered. FRED will finish the current iteration of the UE's command list before it breaks out of the UE command. This is convenient for users who wish to write buffers which cannot be interrupted by pressing BREAK -- put the buffer inside a U1E command, and the buffer will execute through to its end even if the BREAK key is pressed.

If a UE command is being executed and FRED encounters three pending BREAKs (i.e. BREAKs which have been recognized but which have not been used because the UE has not reached the end of its current iteration) FRED will stop the UE, even if the current iteration has not finished. In other words, three pending BREAKs are treated like a true error; one pending BREAK only counts as an error once the current iteration is finished.

Regardless of how many U or G commands are currently being executed, six pending BREAKs will terminate the execution of all instructions. If the O+Q option is on, FRED itself will terminate; otherwise, FRED will take its next command from the terminal.

Nine pending BREAKs will result in the message "internal error -- please quit". If two such errors occur, FRED will terminate itself immediately. This means that pressing BREAK often enough will always let you quit FRED no matter what the situation.

When entering multiple BREAKs, you should pause briefly between BREAKs. It takes the system a certain amount of time to realize that BREAK has been pressed.

Copyright © 1998, Thinkage Ltd.