Seven Indian companies have made it to the latest Fortune 500 list of the world's biggest corporations in terms of revenue with the retail giant Walmart topping the global rankings.<br/><br/>Indian Oil Corp is ranked highest at 161st among Indian firms, .<br/><br/>Among the seven Indian companies, four are from the public sector .<br/><br/>Among state-run majors, Indian Oil is followed by banking behemoth SBI, Bharat Petroleum and Hindustan Petroleum.