âHouse Price Index. The HPI is a broad measure of the movement of single-family house prices. The HPI is a weighted, repeat-sales index, meaning that it measures average price changes in repeat sales or refinancings on the same properties. This information is obtained by reviewing repeat mortgage transactions on single-family properties whose mortgages have been purchased or securitized by Fannie Mae or Freddie Mac since January 1975.
The IBM 305 RAMAC was the first commercial computer that used a moving-head hard disk drive for secondary storage. The system was publicly announced on September 14, 1956, with test units already installed at the U.S. Navy and at private corporations. RAMAC stood for Random Access Method of Accounting and Control, as its design was motivated by the need for real-time accounting in business.
Secondary Storage. The disk drives in the computer are the most common form of secondary storage. The disk drive is nonvolatile and retains the information written to it after the power is turned off to the computer. Because it is a mechanical device, the disk drive is much slower than primary storage devices. All nonvolatile storage devices fall into the secondary storage class, including optical and tape drives.