The offer has already been approved by the Ilog board, and IBM will pay a 56 percent premium to buy the company, which makes business rules management systems software.

Ilog will "strengthen our BPM [business process management] and SOA [service-oriented architecture] position by providing customers a full set of rule management tools for complete information and application lifecycle management across a comprehensive platform including IBM's leading WebSphere application development and management platform", IBM said in a statement.

Ilog will not be alone in this task. In the past five years, IBM has spent $21bn (£10bn) on buying 70 software companies, of which the biggest was Cognos, according to Reuters. IBM bought the business intelligence company for $5bn in January.

The IBM-Ilog deal is subject to a minimum tender offer of 66.67 percent of the share capital and also subject to clearance by US and EU antitrust authorities. The offer in France will only be opened for acceptances once the AMF (the French stock market regulators) and the French Ministry of Economy have granted clearance, IBM said.

On Monday, Ilog also announced its fourth-quarter results. Revenue for the quarter was $46.1m, which compared with revenue of $46.3m for the same quarter last year. Revenue for the financial year was $181m, which was up 12 percent over the previous year.