This document provides examples and explanations of how to use the present perfect tense in English. It discusses using the present perfect with time phrases like "since" and "for". Some key points: 1. The present perfect is formed with have/has + the past participle. It is used to talk about something that began in the past and continues into the present. 2. Bill Gates has been the CEO of Microsoft since 1975 and millions of people have used his computer programs for the past three decades. 3. "Since" is used with a specific point in time to indicate when something started, while "for" is used with a length of time to indicate how long something has lasted.