It was single tasking, but usually there was no need to close the editor to launch the compiler and test the program. IIRC, QBASIC compiled and ran the program on one of the F keys; even EDIT.COM had a subshell.
Turbo Pascal (and its sibling Turbo C) also had a text-mode IDE that could open multiple files, had mouse support, syntax highlighting etc. and if you ran your program, it would run it and when it was finished you were back in the IDE. You could even set breakpoints and step through your code.
