After delays of almost a year, an upgraded operating system for the Blackberry Playbook tablet has been released. Playbook 2.0, a free upgrade, adds a built-in email function to the device which was first launched in April 2011. Canada-based Research in Motion (RIM) had promised the upgrade within 60 days of the device's release. Last month the company's co-chief executives stepped down amid faltering sales figures. Mike Lazaridis and Jim Balsillie were replaced at the helm of RIM by the company's chief operating officer Thorsten Heins. This upgrade for the Playbook - RIM's first foray into the tablet market - also sees built-in calendar and contacts functions added, as well as tighter integration with social networks such as Twitter and LinkedIn. Price drop David Smith, RIM's senior vice-president of mobile computing, said: "Building on the Blackberry Playbook tablet's proven web browsing, multimedia and multitasking strengths, the new Blackberry Playbook OS 2.0 introduces a range of new communications and productivity enhancements as well as expanded app and content support." Another new feature, Blackberry Bridge, allows users to control the tablet remotely using a Blackberry smartphone. However, the popular instant-messaging service Blackberry Messenger - known colloquially as BBM - is absent from the upgrade. The Playbook has seen its price reduced considerably since entering the tablet market. By December, the devices had dropped to $200 (£127), from $500 (£317) at launch. In the last quarter, RIM said 150,000 Playbooks had been sold. In comparison, Apple's market-leading iPad sold 15.4 million units in the same period. However, the Blackberry brand still boasts 75 million active subscribers thanks mostly to its smartphone range.