The term 'OLD PC PLATFORM' refers to two operating systems from the 1980s and 1990s: MS-DOS (Microsoft Disk Operating System) and DOS (Disk Operating System). MS-DOS was developed by Microsoft in 1981 and was the most popular operating system for IBM-compatible PCs until the mid-1990s. DOS was developed by IBM in 1981 and was the first operating system for IBM PCs. Both operating systems were widely used in the 1980s and 1990s, but have since been replaced by more modern operating systems such as Windows and Mac OS.