How compatible is FreeBASIC with QuickBasic?
The FreeBASIC built in graphics library emulates the most used QB graphics modes (modes 7,12,13) and implements all the drawing primitives featured in QB. Most compatibility problems arise from the use of 8086-DOS-hardware specific low-level techniques in the old QB programs. VGA port programming, DOS interrupts, memory segment switching, poking to the screen memory or music playing using the PC speaker are not directly supported, even if they can be supported/emulated by external libraries. Other issues in porting old QB programs, like variable name clashes with new FB keywords, variables with the name of a QB keyword plus a type suffix, default integer size being 32 bits in FB, are addressed by running FreeBASIC with the commandline switch -lang qb .
