Well-received updates from software stocks have sent the sector higher.Financial software provider Misys is to return more than $1bn to shareholders after selling the majority of its stake in its Allscripts subsidiary. The news sent the company's shares up by 20%.Meanwhile, the recent surge in the share price of video search engine firm blinkx continues after its announcement that it has launched four add-on modules for the popular Internet Explorer 8 web browser.The oil sector is under pressure, with BP's slide continuing as Barack Obama cranks up his rhetoric over the oil slick in the Gulf of Mexico and fears mount over the prospect of a dividend cut to help pay for the clean-up.In other oil sector news, Tullow Oil has found oil at its Mahogany-5 appraisal well immediately to the southeast of the Jubilee field offshore Ghana, but its shares are also lower.Top performing sectors so far todaySoftware & Computer Services 635.51 +2.16%Mining 19,936.36 +1.68%Banks 4,566.28 +1.45%Beverages 8,385.84 +1.41%Personal Goods 12,644.72 +1.37%Bottom performing sectors so far todayOil & Gas Producers 6,811.88 -1.24%Construction & Materials 3,178.88 -0.48%Gas, Water & Multiutilities 3,864.18 -0.37%Chemicals 4,852.61 -0.33%Industrial Metals & Mining 4,926.33 -0.26%