CPM may refer to any of the following:
1. CP/M is an 8-bit operating system created by Gary Kildall in 1974 while working at Intel for their new processors. By 1977, CP/M was the most popular operating system in the PC industry. In 1981, Microsoft purchased the rights to an unauthorized clone of CP/M which it marketed to IBM as PC-DOS for the first IBM PC. For all other PC OEMs, Microsoft marketed PC-DOS as MS-DOS.
2. Short for cost per mile or cost per thousand, CPM is a measure of ad impressions and an industry standard for selling ads on websites. The 'M' is from the roman numeral for "thousand." Sites that sell advertising guarantee an advertiser a certain number of impressions and set the rate based on that guarantee times the CPM rate.
For example, a website that guarantees 50,000 impressions, at a CPM rate of $30 costs the advertiser $1,500. A CPM is determined with [ (CPM * impressions) / 1000 ] or [50 * 30], the 50 representing the 50 in 50,000.