The US nuclear weapons force still uses a 1970s-era computer system and floppy disks, a government report has revealed. The Government Accountability Office said the Pentagon was one of several departments where "legacy systems" urgently needed to be replaced. The report said taxpayers spent 61bn ( 41bn) a year on maintaining ageing technologies. It said that was three times more than the investment on modern IT systems. The report said that the Department of Defence systems that co-ordinated intercontinental ballistic missiles, nuclear bombers and tanker support aircraft "runs on an IBM Series-1 Computer - a 1970s computing system - and uses eight-inch floppy disks".