we use the present for :- 1.actions in a period of time up to the present: a-without time words: Mr Ragab has been to London and Paris. b-with (ever)and(never) : Have you ever been to London? No,I,ve never been to London. c-with (just,already and yet: Ow! I,ve just hit my foot! He,s already had his dinner . He hasn,t finished his homework yet. 2. actions which began in the past and continue into the present: I,ve been here for an hour . (for period of time ) I,ve been here since three o,clock.(since point in time) 3.past actions which have an effect on the present: Smeone has broken my window. (That,s why the glass is on the floor.) She,s finished her homework.(That,s why she,s put her books away.)

The perfect tense is best understood as a whole. In English, we use the perfect tense when TWO events happen, and we want to be clear about which is completed first. In this sense, the word "perfect" means "fully completed". PAST PERFECT: This tense is used when TWO events were BOTH completed in the PAST. Example: Event 1 - I studied hard for a test. Event 2 - I entered the class to take the test. Both of these happened in the past, but studying was completed ("perfected") FIRST. I show this with the PAST PERFECT tense, and leave the second event in the simple past: "I HAD STUDIED hard for the test, so I ENTERED the classroom confidently." FUTURE PERFECT: Here, TWO events will happen in the future. But one of the events will be completed ("perfected") before the other. We but the first of the two events in the FUTURE PERFECT and the second event in what looks like the SIMPLE PRESENT (note this!). I say it "appears" to be the simple PRESENT, because we do not use "will"; however, this is merely because one "will" is sufficient for both verbs, given that a conjunction is used. Example: Event 1 - We will drive all night. Event 2 - We will arrive in California. Driving all night will be finished first, so we put that part in the FUTURE PERFECT. Arriving in California will look like the simple PRESENT: "By the time WE ARRIVE in California, we WILL HAVE DRIVEN all night." PRESENT PERFECT: Here, the second event is always assumed to be "RIGHT NOW!" It is not expressly stated. It is understood. Example: Event 1 - I went to Disney World. Event 2 - (THE PRESENT - RIGHT NOW) "I have been to Disney World ten times." This is understood as: "I have been to Disney World ten times (before right now)." This tense is used when it is assumed, likely or hoped that the action will CONTINUE into the future. [cont. below]

Consider: Simple Past: "I went to Disney World." Here, the focus is on ONE TRIP to Disney World that happened in the past. It shows no indication of whether the person will ever go again. The focus is on THAT TRIP IN THE PAST. Past Perfect: "I had been to Disney World ten times before I went for my honeymoon." Here, we are showing that 1.) "going to Disney ten times" was completed BEFORE 2.) the honeymoon trip to Disney. Present Perfect: "I have been to Disney World ten times." This is understood as "I have been to Disney World ten times (before now) (and I will likely go again someday)." It carries a hope, wish or likelihood of going again, even though that is not said outright.

No doubt that present prefect tense is little bit tricky especially for the beginner. Since I also learned this from a video teaching recently, Let me share what the teacher of the video teaching said. Present Prefect Tenses describes action happing in the past up to the present, formed by taking the present of verb 'to have' or 'to has' depending on what gender of the subject is, and past participle of verb of the sentence. It just like. have or has + past participle of verb e.g He has cooked. In my opinion, when to use this tense depends on what meaning you want to express. And I think this tense is aways used when the action or the stage of being should be emphasize. However, I have not totally mastered this knowledge.

These type of questions may be Googled (www.google.com) or use www.ask.com http://www.englishpage.com/verbpage/presentperfect.html Present Perfect FORM [has/have past participle] Examples: * You have seen that movie many times. * Have you seen that movie many times? * You have not seen that movie many times. Complete List of Present Perfect Forms USE 1 Unspecified Time Before Now We use the Present Perfect to say that an action happened at an unspecified time before now. The exact time is not important. You CANNOT use the Present Perfect with specific time expressions such as: yesterday, one year ago, last week, when I was a child, when I lived in Japan, at that moment, that day, one day, etc. We CAN use the Present Perfect with unspecific expressions such as: ever, never, once, many times, several times, before, so far, already, yet, etc. Examples: * I have seen that movie twenty times. * I think I have met him once before. * There have been many earthquakes in California. * People have traveled to the Moon. * People have not traveled to Mars. * Have you read the book yet? * Nobody has ever climbed that mountain. * A: Has there ever been a war in the United States? B: Yes, there has been a war in the United States. How Do You Actually Use the Present Perfect? The concept of "unspecified time" can be very confusing to English learners. It is best to associate Present Perfect with the following topics: TOPIC 1 Experience You can use the Present Perfect to describe your experience. It is like saying, "I have the experience of..." You can also use this tense to say that you have never had a certain experience. The Present Perfect is NOT used to describe a specific event. TOPIC 2 Change Over Time See also http://www.geocities.com/SiliconValley/2527/presentperfect.html