U.S. computer software giant Microsoft said Monday that it plans to buy back another $40 billion of its stock. In a statement, the company said the buyback would continue until September 2013. The statement said Microsoft had completed a previously pledged $40 billion stock repurchase program. The tech company, which has seen its stock price fall by 30 percent this year, also announced a quarterly dividend of 13 cents a share, an increase of 18 percent over the dividend the previous quarter. “These announcements illustrate our confidence in the long-term growth of the company and our commitment to returning capital to our shareholders,” said Chris Liddell, chief financial officer of Microsoft. The company has been assigned the highest ‘AAA' corporate credit rating by two ratings companies. Microsoft revenues exceeded $60 billion in fiscal 2008.