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.
The first digital tape recorder was demonstrated in Japan in 1967, with the first digitally mastered records appearing on the Denon label in 1972. The first commercially available digital audio recorder was the Sony PCM-1. Introduced in 1977, the PCM-1 converted an incoming analogue signal into a digital one, which was then recorded onto a standard video cassette in a VCR. Initially, digitally mastered records were still released on vinyl disks in the analogue format. In 1982, however, Sony and Philips released the first compact discs and players. On a CD, the digital information was embodied as millions of microscopic bits in the reflective aluminum coating of the disk.