Compaq Computer Corp said it will next year introduce handheld computers that offer mobile communication functions and traditional personal computer and networking capabilities: it says it has been working with Microsoft Corp through their recently announced Frontline Partnership to lay the foundation for handheld Mobile Companions; the company, whose shares were under pressure yesterday alongside those of Apple Computer Inc (see page five), said it was the only personal computer maker to increase its share of the US market for notebook computers during the quarter that ended March 30, and that the Contura and LTE Lite laptop took 17.6% for all sales channels.