ST. LOUIS (AP) _ Billionaire technology mogul Paul Allen is acquiring Charter Communications, the nation's 10th-largest cable company, for $4.5 billion to take a second big step into the cable industry.

Allen, the co-founder of Microsoft Corp., said today he will combine Charter with his recently acquired Marcus Cable Co. to form the country's No. 7 cable company, serving 2.4 million customers.

The acquisition of privately held Charter is Allen's largest personal investment yet. Allen has been building a portfolio of entertainment and technology companies to create what he calls a ``wired world.''

Allen bought Marcus Cable, the nation's biggest privately held cable company, for $2.78 billion in April with an eye on using cable lines for faster Internet access, interactive television and other high-tech services.

Jeffrey Marcus, founder of Dallas-based Marcus Cable, will serve as chairman of Allen's new cable company, which will be based in Charter's hometown of St. Louis.

Charter chief executive Jerald L. Kent will become the CEO of the combined organization, which has not yet been named.

``Paul's longtime vision of a `wired world' is not a vision of the future, anymore,'' Kent said. ``The world Paul has been talking about for the past two decades is here, now and we share that vision and are ready to make it a reality.''

Allen, who co-founded Microsoft with Bill Gates in 1975, also owns basketball's Portland Trail Blazers and football's Seattle Seahawks. Forbes magazine last month estimated Allen's net worth at $21 billion.