When the MS-DOS operating system came out, it incorporated the GWBASIC.EXE or BASICA.EXE interpreters. GWBASIC ("Gee Whiz") incorporated graphics and a screen editor and was compatible with earlier BASICs.
QBASIC was more sophisticated. Version 4.5 had a full screen editor, debugger and compiler. The compiler could also produce executable files but to run these a utility program (BRUN44.EXE) had to be present. Thus source code could be kept private.