The IBM Personal Computer Turns 25

July 12, 2006 — -- Twenty five years ago this week, Prince Charles and Princess Diana were on their honeymoon, the Space Shuttle had one flight … and -- oh, by the way -- the world was changing.

This is the 25th anniversary of the IBM 5150. It was hardly the first personal computer -- insolent little startups such as Apple and Commodore had come first -- but IBM's entry into the P.C. market almost instantly made the desktop computer a fixture of modern life.

"We thought it was going to be successful; but taking the world by storm, as it turned out it did? I never remotely conceived of that," says David Bradley, an IBM engineer, now retired, who was on the 12-member team originally assigned to design the machine. They worked for a year, around the clock, in secret.

The machine they came up with came in a beige box, with a keyboard and a monitor that displayed green text on a black background. Color graphics were extra. IBM machines would not come with a mouse for nearly another decade.

The 5150 had a processor that did calculations at 4.77 megahertz -- about a thousandth the speed at which personal computers run today. It had no hard drive; users stored data on a cassette recorder, unless they wanted to spend extra on a floppy drive. It had 16 kilobytes of RAM -- random access memory. If you have a machine today with one gigabyte of memory, it is about 65,000 times more powerful.

IBM said it expected to sell 250,000 machines in five years. Instead, it sold a million.

Today, according to several surveys, about 70 percent of American households have at least one computer. The personal computer has become your post office, your music collection, the digital shoebox in which you keep your old pictures. If you're online, you can find almost any information, or anything, through your computer.

"You know, what surprised me the most is that it's lasted this long," said Christopher Garcia, assistant curator at the Computer History Museum in Mountain View, Calif., "that no one else at any point came up with something better, which is unthinkable.