The PlayStation Portable is the only handheld video game console to use an optical disc format, Universal Media Disc (UMD), as its primary storage medium. Sony first announced development of the PlayStation Portable at a press conference before E3 2003. Although mock-ups of the system were not present at the press conference or E3, Sony did release extensive technical details regarding the new system. Then-CEO of Sony Computer Entertainment Jose Villeta called the device the "Walkman of the 21st Century" in a reference to the console's multimedia capabilities. Despite the high price, the console's PAL region launch was a resounding success, selling more than 185,000 units in the UK alone, selling out of all stock nationwide in the UK within three hours of launch, more than doubling the previous first-day sales record of 87,000 units set by the Nintendo DS.
