IBM PCs had BASIC built into the ROM (licensed from Microsoft). BASIC.COM and BASICA.COM (advanced BASIC) which came with PC-DOS would call subroutines in the R

IBM PCs had BASIC built into the ROM (licensed from Microsoft). BASIC.COM and BASICA.COM (advanced BASIC) which came with PC-DOS would call subroutines in the ROM (except for ones that had errata), so you needed a real IBM PC to run it. Clones didn't have BASIC in ROM, so MS-DOS came with GWBASIC.COM which included all the subroutines. Turns out GWBASIC runs faster than BASICA because the RAM had faster access than ROM. More details at: https://en.wikipedia.org/wiki/IBM_BASIC https://en.wikipedia.org/wiki/IBM_BASIC