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IBM Cassette BASIC was a version of the Microsoft BASIC programming language licensed by IBM for the IBM PC. It was included in the BIOS ROM of the original IBM PC. Cassette BASIC provided the default user interface if there was no floppy disk drive installed, or if the boot code did not find a bootable floppy disk at power on. The name Cassette BASIC came from its use of cassette tapes rather than floppy disks to store programs and data. GW BASIC is standalone compatible successor of IBM Cassette BASIC, which doesn't require ROM to run.
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