Osi Model Explained Essay Example for Free

Osi Model Explained Essay This paper discusses the Open System Interconnection reference model (OSI model) and the organization and function of its 7 layers. The OSI model is the most commonly referenced networking communication model, but it is rarely implemented in its entirety Ciccarelli et al. (2008). The OSI model provides a common frame of reference for discussing various hardware and software issues (Ciccarelli et al., 2008). The layers are the: Application, Presentation, Session, Transport, Network, Data Link and Physical (Ciccarelli et al., 2008). When data is sent, the user application sends data down through the layers of the model, which are self contained and have specific functions. Each layer adds information to the data pertaining to the layer’s control. The OSI model was created in 1984 by the International Standards Organization (ISO) in response to the need for a set of standards to allow computers to communicate through a network according to Ciccarelli et al. (2008). Additional rationales for the OSI model are given and most significant among them is that it was designed to overcome interoperability issues with networking products from disparate vendors (Ciccarelli et al., 2008; Davis, 2008). Other reasons given for creating the OSI model include: †¢ to clarify general functions of internetworking (Rivard Roherty, 2008) †¢ to divide the complexity of networking into smaller more manageable bites (Rivard Roherty, 2008) †¢ to simplify troubleshooting (Ciccarelli et al., 2008) †¢ to allow developers to change and improve components of a networking stack without altering the function of other layers (and the need to re-write them) (Rivard Roherty, 2008) A key to the understanding the OSI model is the idea of data passing down through the OSI model layers in one computer, then across a network media and then up through the OSI model layers in a second computer (Hill, 2002). As data flows down through the OSI model layers, each layer that has an applicable protocol, labels the data packet with a header and a trailer specific to the layer this is known as encapsulation (Hill, 2002). On the recipient computer, the data header and trailer is removed after its values are utilized (or de-encapsulated) as the data packet travels up the corresponding layer of the OSI model (Ciccarelli et al., 2008; Hill, 2002). Each layer prepares the data for the adjacent layer before it is forwarded by adding header and trailer data to the data. Layer responsibilities and definitions: (7) Application: User programs communicate with API’s in the application layer which allows user programs to contain very little networking code themselves (Hill, 2002). The application layer provides access to the network protocol stack. DNS operates at the application layer. Other important examples of protocols operating at this layer are: http, POP3 (email protocol), SMTP (email transport protocol), IMAP (internet message access protocol), FTP and Telnet – includes network printing and database services. Layer devices include: hosts, servers, PC’s and laptops, cellular phones [pic](Ciccarelli et al., 2008; Hill, 2002; Messer, 2010). (6) Presentation: This layer ensures that format of data input from the application layer is in a form suitable for transport over the network, and that it can be interpreted by the receiving node. Translates character sets such as ASCII, EBCDIC and Unicode for compatibility with remote nodes. This layer compresses and encrypts da ta as needed [pic](Ciccarelli et al., 2008; doogie966, 2011; Hill, 2002; Messer, 2010). (5) Session: Sets up, maintains and breaks-down connections between network endpoint applications; negotiates whether transmission will be simplex, half-duplex, or full duplex. Simplex is similar to a broadcast in that it is one way; half-duplex is two way transmission, but only one direction at a time; full duplex is two-way communication at the same time using different channels to manage send and receive traffic [pic](Ciccarelli et al., 2008; Hill, 2002; Messer, 2010; Rivard Roherty, 2008). Remote procedure calls originate from the session layer (doogie966, 2011). (4) Transport: Provides reliable transport using connection-oriented services (transmission control protocol -TCP) and connection-less oriented services (user datagram protocol, or UDP). Important functions provided by this layer are flow control, error detection and error recovery. Flow control starts before data is actually sent. The transmitting node sends the receiving node a message indicating that it is about to t ransmit data to the receiving node. The receiving node acknowledges the receipt of the notice from the sender – then data is transmitted. Flow control utilizes TCP protocol to ensure delivery of data. TCP is associated with connection-oriented service where communication is assured. Flow control also manages data transmission speed through a windowing process. A TCP window is that specific amount of data that can be sent before an acknowledgement is required by the receiving node. This prevents the receiving device from being overwhelmed by data volume that is can’t process fast enough. Connection-less transmissions (UDP) offers no error detection or recovery mechanism and is faster without the overhead of recovery requirements [pic](Ciccarelli et al., 2008; Hill, 2002; Messer, 2010; Rivard Roherty, 2008). (3) Network: Responsible logical addressing using IP protocol, or path determination (routing) and packet (datagrams) delivery [pic](Ciccarelli et al., 2008; Hill, 2002; Messer, 2010; Rivard Roherty, 2008). When traffic arrives at the network layer, header/trailer information is added or taken away that includes the logical addressing data or IP. IP addressing allows a router to route packets to remote nodes IP. There are two ways routing can be processed one is source routing. In source routing, IP data for every router on the path to the destination is included in the data packet. The routing method calls for the source and destination IP information to be contained within the packet. Once on the network, routers use the source and destination addresses to forward the packet to the next router, or hop, on the path to the destination (Ciccarelli et al., 2008). (2) Data Link: Consists of Logical Link Control Layer and the Media Access Control Layer: MAC layer Responsible for physical addressing or for getting traffic onto the network using the MAC protocol, this layer is responsible for NIC (L1L2) control. Switches and bridges operate at this layer, since they are using the MAC physical address of the sender/receiver devices to determine which port on a switch to use, or whether to let traffic pass (bridge). Switches also operate at layers 3 and 4 [pic](Ciccarelli et al., 2008; Hill, 2002; Messer, 2010). Media access control (MAC Address) addressing is managed and added/removed from traffic at this layer. Logical addresses (IP) are not considered at this layer. LLC sublayer bridges the MAC sublayer to the upper layer protocols. 1) Physical Responsible for physical devices such as NIC’s(L1 2), cabling, fiber, coax, wireless, hubs, connectors (e.g. RJ-45, BNC and for implementing standards for physical configuration of connectors such as TIA/ETA (RJ-45). Also, the physical layer manages signaling and voltages required to transmit data [pic](Ciccarelli et al., 2008; Hill, 2002; Martin, Not Given; Messer, 2010). References Ciccarelli, P., Faulkner, C., FitzGerald, J., Dennis, A., Groth, D., Skandier, T., Miller, F. (2008). Networking Basics. Hoboken, NJ: John Wiley Sons, Inc. Davis, D. (2008). Cisco Administration 101: Understand the OSI model to become a better Cisco troubleshooter. Retrieved 2/13/2013, 2013, from http://www.techrepublic.com/blog/networking/cisco-administration-101-understand-the-osi-model-to-become-a-better-cisco-troubleshooter/556 doogie966. (2011). OSI protocols and devices. from http://quizlet.com/6089965/osi-layer-protocols-devices-flash-cards/ Hill, B. (2002). Cisco: The Complete Reference: McGraw-Hill/Osborne Media. Martin, U. o. T. a. (Not Given). EIA/TIA 568A 568B Standard. Retrieved February 16, 2013, from http://www.utm.edu/staff/leeb/568/568.htm Messer, J. (2010). The OSI Model CompTIA Network+ N10-004: 4.1. Retrieved February 14, 2013, from https://www.youtube.com/watch?feature=endscreenv=W438koUR04oNR=1 Rivard, E., Roherty, J. (2008). CCNA Flash Cards Practice Pack (Third ed.): Cisco Systems, Inc.

Macbeth :: essays research papers

Macbeth was one of William Shakespeare’s finest plays. Although many people have read Macbeth, not many people know that King Macbeth of Scotland actually existed and what influenced Shakespeare to write about him. English culture and society as well as the historical figure Macbeth impacted Shakespeare’s infamous play. The historical King Macbeth reigned in Scotland for 17 years from 1040-1057. He had a wife named Coruoch and a stepson named Luloch. Although Macbeth did kill Duncan, he was not the gentle king as described in Macbeth. Killing a king was not uncommon at this time as, Macbeth’s 7-9 predecessors were killed as well. In 1050, Macbeth went on a religious pilgrimage to Rome to seek absolution for Duncan’s death. Unlike Macbeth, Malcolm (rather than Macduff) killed the historical Macbeth. Luloch, known as the â€Å"Idiot,† reigned for five months after Macbeth’s death until Malcom overthrew him. Although there are differences between Shakespeare’s Macbeth and the historical figure Macbeth, it is obvious that Shakespeare based his character on this Scottish king. The person who influenced Shakespeare to write Macbeth was King James I of England, who reigned from 1566 to 1625. King James, who was also known as King James 6 of Scotland, succeeded the throne of Queen Elizabeth. James’ mother, Mary Queen of Scots, was known as a tragic queen since she killed James father. At age sixteen, rivals kidnapped James and at age 20, James’ mother was executed. King James was intellectual, scholarly, and an â€Å"insatiable curiost.† His ideal of heaven was the Oxford Library. In 1584, while he was only 18 years old, James wrote Essays of Apprentice in Fine Arts of Poetry. He discussed a new translation of the bible, The Authorized Version, which is the most popular bible today. James also wrote in defense of the Divine Right of Kings- that kings were chosen by God, but they must rule well. King James succeeded in ruling an authoritarian government, but he ruled no better than today’s democratic governments. He was known as the wisest fool in Christendom. James was also eager for social reform. He wrote A Counterblast to Tobacco, which is much like the anti-smoking campaigns of modern times. When Shakespeare wrote Macbeth, he was obviously aware of James concern with witchcraft. King James wrote the Daemonologie, an account of his experiences with witchcraft. Once a witch tried to melt James’ image in wax, and another witch tried to poison him with toad venom.

Present Perfect

Introduction The theme of the present paper is â€Å"The Present Perfect†. The main goal of the work is to identify the main features of the Present Perfect and to present the cases of its use, basing on the theoretical and scientific works of Russian, English linguists. The objectives of the work, in their turn, represent ascending steps to the main goal of the project: 1. to give the definition to the present perfect; 2. to present the ways of formation of the present perfect tense; 3. to investigate cases of its use in the sentence and in American and British English compare them ; 4. o draw the line of demarcation between the use of the Present Perfect and the Past Simple Actuality of the work is the significance of the present perfect tense in the English language. That is a linguistic phenomenon, which exists not in every language and which is replaced by other tenses while translated into other languages appears to be one of the main constituents of English grammar. Nov elty of the paper lies in communicative approaches to linguistic analysis of the use of the present perfect tense aimed at acquiring the communicative competence.Theoretical value of the paper is based on the analyzed data taken from the works of American and English prominent linguists. Practical value of the work may be useful in practical grammar or in a daily use. The course paper consists of 4 parts; Introduction, Main Part, Conclusion and Bibliography. The Main Part consists of 2 chapters. Thus, Chapter I of the present paper is devoted to the general remarks the present perfect tense and comprises 3 points: 1. History of the Present Perfect Tense 2.The Formation of the Present Perfect 3. Differences between the Past Indefinite and the Present Perfect In this chapter we can find out general information about the origin of perfect tenses and the present perfect tense itself, and the ways of forming the present perfect, and the differences between the past simple and the present perfect in use. Chapter II includes 2 points: 1. The use of the Present Perfect in the sentence 2. Differences in use of the Present Perfect in American and British English.This chapter is devoted to the practical side of the work. We investigate the use of the present perfect in the sentence and the differences of the use of the present perfect in American and British English. Chapter Two can be interesting with the presentation of peculiar characteristics of the use of the present perfect of two main trends of English: American and British English. The reason I chose the theme â€Å"The Present Perfect† was the situation of not having this tense in the for us familiar languages: Russian and Kyrgyz.The Past Simple and The Present Perfect are replaced by only one tense in Russian called â€Å" †. The nature of this tense seems to be familiar for the learners of English at first sight, but there are many exceptions and special cases of their use. CHAPTER I: What the Pr esent Perfect Tense is 1. 1 History of Perfect Tenses and the Present Perfect The Present Perfect is an analytical form which is built up by means of the auxiliary verb to have in the Present Indefinite and the participle of the notional verb (e. g. I have worked. He has worked, etc. The word â€Å"perfect† in the name came from a Latin root referring to the idea of completion—of being now finished—rather than to perfection in the sense of â€Å"no flaws† (although the latter sense of â€Å"perfect† actually evolved by extension from the former, because something [for example, a drawing or a piece of pottery] is finished when it no longer has any flaws). So perfect tenses were named thus because of the idea that (in some uses in some languages, at least) they referred to actions that were finished with respect to the present (for example, â€Å"I have eaten all the bread† involves a sense of finality).However, as seen above, the name is a mi snomer in the sense that not all uses of present perfect constructions involve an idea of completion. In Old English the verb to have, used as the predicate in the sentence, was sometimes followed by direct object with participle II of a transitive verb attached to it on the function of a predicative adjective. The participle agreed in number, gender, case with the direct object. He has that book written= . As the state of the object ( written) was the result of the accomplished action, the mind of the speaker began to be interested in he action. The construction did not show whether the action expressed by participle II was performed by the subject of the sentence or by some other agent. It was from constructions where the subject of the sentence was the doer of the action denoted by the past participle, that the modern English perfect form developed. The participle lost its form of agreement with the noun-object and changing its place (He has written), became closely connected with the verb to have. Both elements lost their independent meaning and merged into one sense unit –the analytical form of the Modern English Perfect.He has written that book – the action of writing is accomplished by him at present and as a result of it the book is in a written state. Thus, what was originally a free syntactical combination has now turned into an analytical tense form. Such constructions, in which the doer of the action expressed by the participle was not the subject of the sentence, have still survived in Modern English as free syntactical combinations: He had three horses killed under him. I have my dress made here. Killed and made are still predictive adjectives to the direct object horses and dress.In construction with the verb to be, participle II of an intransitive verb was used as the predicative to the subject with which agreed in number, gender and case, and the verb to be had the function of a link-verb in a compound-nominal predicate: He i s ? ecumen = O? . When to have and to be –forms turned into perfect, the verb to have began gradually to be used as an auxiliary verb with both transitive and intransitive verbs: I have seen her. I have come. As a survival of the old constriction, to be is still used when the state is stressed: May Fielding was already come; and so was her mother. Dickens) When he was gone, my mother asked me all about the day I had had†¦ (Dickens)He is gone to the Leas†¦ (Bronte) The present perfect is a grammatical combination of the present tense and the perfect aspect, used to express a past event that has present consequences. An example is â€Å"I have eaten† (so I'm not hungry). Depending on the specific language, the events described by present perfects are not necessarily completed, as in â€Å"I have been eating† or â€Å"I have lived here for five years. The present perfect is a compound tense in English, as in many other languages, meaning that it is form ed by combining an auxiliary verb with the main verb. In modern English, the auxiliary verb for forming the present perfect is always to have. * I have eaten * You have gone * He has arrived In many other European languages, the equivalent of to have (e. g. , German haben, French avoir) is used to form the present perfect (or their equivalent of the present perfect) for most or all verbs. However, the equivalent of to be (e. g. German sein, French etre) serves as the auxiliary for other verbs in some languages such as German, Dutch, French, and Italian (but not Spanish or Portuguese). Generally, the verbs that take to be as auxiliary are intransitive verbs denoting motion or change of state (e. g. , to arrive, to go, to fall). In many European languages, including standard German, French and Italian, the present perfect verb form usually does not convey perfect aspect, but rather perfective aspect. In these languages, it has usurped the role of the simple past (i. . preterite) in sp oken language, and the simple past is now really only used in formal written language and literature. In standard English, Spanish, and Portuguese, by contrast, the present perfect (perfect) and simple past (perfective aspect) are kept distinct. The Present Perfect form denotes an action completed before the present moment (and connected with it) or before a definite moment in the past or future. It is formed by means of the auxiliary verb to have in the required tense and Participle II of the notional verb 1. The formation of the Present Perfect 1. The Present Perfect is formed by means of the Present Indefinite of the auxiliary verb to have and Participle II of the notional verb. 2. In the interrogative form the auxiliary verb is placed before the subject. In the negative form the negative particle not is placed after the auxiliary verb. Affirmative| Interrogative| Negative| I have workedHe has workedShe has workedWe have workedYou have workedThey have worked| Have I worked? Has h e worked? Has she worked? Have we worked? Have you worked? Have they worked? I have not workedHe has not workedShe has not workedWe have not workedYou have not workedThey have not worked| 3. The contracted affirmative forms are: I’ve worked He’s worked You’ve worked The contracted negative forms are: I haven’t worked He hasn’t worked You haven’t worked 4. The negative-interrogative forms are: Has she not worked? Hasn’t she worked? Have you not worked? Haven’t you worked? 1. 3 Differences in between the Past Indefinite and the Present Perfect It follows from the rules above that the Present Perfect is not used when there is an indication of past time in the sentence.It is the Past Indefinite that is used in this case because the mention of the definite past time ties the action to the past- time sphere as it were, and it cannot break through to the present. e. g. â€Å"Put on your clothes at once and come with me. † †Å"But what is it? Has something happened? † â€Å"I'm afraid so. Your husband was taken ill this afternoon. † â€Å"M. Poirot, you have no idea of what I have gone through. † â€Å"I know your wife died just over a year ago. † Similarly, it is the Past Indefinite that is used in questions introduced by when. e. g.When did you actually arrive? When did you change your mind? The Past Indefinite is also used in special questions beginning with where and how when they refer to the past events. The Present Perfect is not common here because the attention in such sentences is drawn to the circumstances of the action rather than to the occurrence itself, which means that the speaker has a definite action in mind. e. g. â€Å"Where did your uncle receive his guests? † â€Å"Right here. † â€Å"How did he get in? † I asked, and Evans said, â€Å"Oh, he has a key. † â€Å"Where is my hat?Where did I leave my hat? † Note. The questi on Where have you been? can be asked of the person who has just come. e. g. ‘Hello, Mum. I'm sorry I'm late† â€Å"Where have you been? † In all other cases it should be Where were you! e. g. â€Å"Did the party go off nicely? † â€Å"I don't know. I wasn't there. † â€Å"Where were you? ‘ In special questions beginning with interrogative words other than those mentioned above (e. g. who, what, why, what †¦ for and other), both the Present Perfect and the Past Indefinite are possible. The choice depends on the meaning to be conveyed.If reference is made to an action which is past or definite in the minds of the people speaking, or if there is a change of scene, the Past In definite is used; if reference is made to an action which is still valid as part of the present situation, the Present Perfect should be used. e. g. â€Å"What have I done against you? † she burst out defiantly. â€Å"Nothing. † â€Å"Then why can't we ge t on? † â€Å"I know she gave him a good scolding. † â€Å"What did he do? † Looking up at her he said: â€Å"Dorothy's gone to a garden party. † â€Å"I know. Why haven't you gone too? Why didn't you speak to my father yourself on the boat? Note 1. As to general questions, the Present Perfect as well as the Past Indefinite may be found in them because they may inquire either about new facts which are important for the present or about events that are definite in the mind of the speaker. Note 2. In the following example the verb to be is used in the meaning ‘to visit', ‘to go'. Hence it takes the preposition to after it. It is noteworthy that to be acquires this meaning only if used in the Present Perfect or the Past Perfect. e. g.Renny said: â€Å"He has been to Ireland too† â€Å"Have you been to a symphony concert? † he continued. Note 3. The combination has/have got may be used as the Present Perfect of the verb to get (which is not very common, though). e. g. I don't know what's got into Steven today. He has got into financial difficulties and needs cash. But it is often used as a set phrase which has two different meanings  Ã¢â‚¬â€ ‘to possess' (a) and ‘to be obliged' (b). e. g. a) â€Å"Have you got a telephone? † she looked round the room. â€Å"I don't think we've got any choice,† said Francis, ) â€Å"No† he said loudly, â€Å"there are some risks you've got to take. † â€Å"It doesn't matter what caused it,† said Martin. â€Å"We have got to take the consequences† In this case the time reference also changes  Ã¢â‚¬â€ has/have got is the Present Perfect only in form; it actually indicates a present state of things. Note 4. She is gone is a survival of the old Present Perfect which was formed with certain verbs by means of the auxiliary to be. In present-day English it is to be treated as a set phrase meaning ‘she is not here any lon ger'. CHAPTER II : The Use of the Present Perfect . 1 The use of the Present Perfect in the Sentence The Present Perfect falls within the time sphere of the , present and is not used in narration where reference is made to past events. It follows from that that the Present Perfect is used in present-time contexts, i. e. conversations, newspaper and radio reports, lectures and letters. The Present Perfect has three distinct uses. They will be further referred to as Present Perfect I, Present Perfect II and Present Perfect III. 1) Present Perfect I is the Present Perfect proper.It is used to express an accomplished action which is viewed from the moment of speaking as part of the present situation. Attention in this case is centred on the action itself. The circumstances under which the action occurred appear unimportant and immaterial at the moment and need not be mentioned. e. g. He is very sensitive, I have discovered that. I've had a talk with him. He says he has all the proof he wants. Such news! We've bought a racehorse. â€Å"I've spoiled everything,† she said. His secretary said tactfully: â€Å"I've put off your other appoint- ments for a while. It should be especially noted that though the action expressed in the Present Perfect is regarded as already accomplished, it belongs to the present-time sphere and is treated as a present action. It becomes obvious from the periphrasis: I've heard the doctor's opinion —> I know the doctor's opinion. She's gone off to the woods —> She is in the woods. A similar idea of an accomplished action is also traced in such expressions referring to the present as He is awake. I'm late. The work is done. The door is locked, etc.Since it is the action itself that the Present Perfect makes im- portant, it is frequently used to open up conversations (newspaper and radio reports, or letters) or to introduce a new topic in them. However, if the conversation (report or letter) continues on the same subject, going into detail, the Present Perfect usually changes to the Past Indefinite, as the latter is used to refer to actions or sit- uations which are definite in the mind of the speaker. Usually (but not necessarily) some concrete circumstances of the action (time, place, cause, purpose, manner, etc. are mentioned in this case. e. g. â€Å"You are all right. You are coming round. Are you feeling better? † â€Å"I'm quite all right. But what has happened? Where am I? † â€Å"You're in a dug-out, You were buried by a bomb from a trench-mortar. † â€Å"Oh, was I? But how did I get here? † â€Å"Someone dragged you. I am afraid some of your men were killed, and several others were wounded. † â€Å"Pussy Cat, Pussy Cat, Where have you been? † â€Å"I've been to London To look at the Queen. † â€Å"What did you see there? † â€Å"I saw a little mouse Under her chair. â€Å"As is seen from the above examples, the Present Perfect is us ed to name a new action, whereas the Past Indefinite is used to refer back to a definite action and the attention in this case is often drawn rather to the circumstances attending the action than to the action itself. Note. The functions of the Present Perfect and the Past Indefinite may be in a way compared with those of the indefinite and the definite articles. The indefinite article is used when an object is just named (e. g. Glue me a book. She is a teacher. I have a brother).Likewise the Present Perfect serves to name an accomplished action (see the examples above). Both the definite article and the Past Indefinite are used when an object or an action, respectively, is definite in the mind of the speaker (e. g. The book is on the table. The teacher returned the compositions,) As has been said, Present Perfect I is mainly used to introduce a new topic. But it may also be used to sum up a situation. e. g. â€Å"I've done bad things,† I said, â€Å"but I don't think I coul d have done some of the things you've done. † â€Å"You've so often been helpful in the past. â€Å"I've tried,† said Joseph. We've all been young once, you know. We've all felt it, Roy. â€Å"I'm afraid I've been horribly boring and talked too much,† she said as she pressed my hand. â€Å"Agatha has told me everything. How cleverly you have both kept your secret,† â€Å"You and your wife have been very good to me. Thank you. † In accordance with its main function  Ã¢â‚¬â€ just to name an accomplished action  Ã¢â‚¬â€ the Present Perfect is generally used when [the time of the action is not given. e. g. He sat down. â€Å"You have not changed,† he said. â€Å"No? What have you come for? † â€Å"To discuss things. â€Å"Mr has told me such wonderful things about you. Walter. † â€Å"I haven't thought about it,† she returned. However, sometimes, even though there may be no indication of past time in the sentence, th e Present Perfect cannot be used because reference is made to happenings which are definite in the mind of the speaker (either because the action has already been mentioned or because the situation is very well known to the listener). In this case the use of the Past Indefinite is very common. e. g. Did you sleep well? I didn't understand you. Did you enjoy the play?Did you have a good journey Did you like the book? (trip, ride, flight, day, time)? What did you say? Did you see the accident? Did you hear what he said? I'm sorry I lost my temper. I didn't hear your question. It is possible, however, to use the Present Perfect when there is an adverbial modifier of time in the sentence that denotes a period of time which is not over yet, e. g. today, this morning, this week, this month, this year, etc. e. g. What Rosanna has done tonight is clear enough, (Tonight is not over yet. ) This year we have taken only one assistant. (This year is not over. I have had only one new dress this s ummer,† exclaimed June. (This summer is not over yet. ) Conversely, if the period is over or reference is made to a particular past point of time within that period, the Past Indefinite is used. e. g. â€Å"Did you see the letter in the â€Å"Times† this morning? (It is no longer morning. ) â€Å"No. I haven't had time to look at a paper today,† (Today is not over yet. ) â€Å"Whom do you think I passed in Richmond Park today! † (Today is not over, but the action took place at a particular point of time within today, namely when the person was in Richmond Park. â€Å"I wasn't very well this morning, but I'm perfectly all right now. † (This morning is over. ) Note. It should be noted that sometimes an adverbial modifier of place points to a past period of time. e. g. Did you see him at the theatre? (= when you were at the theatre) I ran into her in Oxford Street. (= when I was in Oxford Street) The Present Perfect may be found with certain adverbs o f indefinite time and frequency such as just (‘ '), not †¦ yet, already, before, always, ever, never, often, seldom, recently, late ly, of late, etc. e. g. She's just missed being run over.I haven't even had coffee yet. He has never made a sixpence by any of his books. Have you heard of him lately? â€Å"What is the point? † â€Å"I've made it clear enough before. † However, the use of the Present Perfect is by no means obligatory with the above mentioned adverbs, because any other finite form may be used with these adverbs if it is required by the situation. e. g. He was studying to be a pianist, but he never touches the piano now. He noticed that the leaves of the chestnut were already beginning to turn yellow and brown. His room was not yet furnished, and he liked it to remain empty. Note 1.Note the use of the Past Indefinite with just now. e. g. I told you just now I had never had time for much fun. Note 2. Russian students of English, under the influenc e of the Russian language, tend to use the adverb already nearly in every sentence containing the Present Perfect. That is not characteristic of the English language as it is sufficient to use the Present Perfect alone to express an accomplished action. The addition of already appears redundant in many cases. Present Perfect II serves to express an action which began before the moment of speaking and continues into it or up to it.This grammatical meaning is mainly expressed by the Present Perfect Continuous. However, the Present Perfect Non-Continuous is found in the following cases: a)Its use is compulsory with stative verbs. e. g. I've known the young lady all her life. I've loved her since she was a child. â€Å"But we've been in conference for two hours,† he said. â€Å"It's time we had a tea break. † b)With some dynamic verbs of durative meaning the Present Perfect is sometimes used instead of the Present Perfect Continuous with little difference in meaning. e. g. â€Å"It's a pretty room, isn't it? â€Å"I've slept in it for fifteen years. † â€Å"I'm glad to meet you,† he said. â€Å"I've waited a long while and began to be afraid I'd not have the opportunity. † He's looked after Miss Gregg for many years now. As to terminative verbs, they can only have the meaning of Present Perfect I and never of Present Perfect II. Since it is often difficult to draw the line between durative and terminative verbs, it is recommended that students of English should use the Present Perfect Continuous with all dynamic verbs to express an action begun in the past and continued into the present. )The Present Perfect is preferred to the Present Perfect Continuous in negative sentences, when it is the action itself that is completely negated. e. g. â€Å"Shall we sit down a little? We haven't sat here for ages. † â€Å"I was just having a look at the paper,† he said. â€Å"I haven't read the paper for the last two days. â⠂¬  â€Å"She hasn't written to me for a year,† said Roy. It is noteworthy that Present Perfect II is associated with certain time indications  Ã¢â‚¬â€ either the whole period of the duration of the action is marked or its starting point.In the former case we find different time indications. Some expressions are introduced by the preposition for and sometimes in (e. g. for an hour, for many years, for the last few days, for a long time, for so long, for ages, in years, in a long while, etc. )- Other expressions have no prepositions (e. g. these three years, all this week, all along, so long, all oneys life, etc. ). e. g. The picture has been mine for years and years. I've felt differently about him for some time. â€Å"Why haven't I seen you all these months? † said Hankins.We haven't had any fun in a long while. I've wanted to go to the sea all my life. The starting point of the action is indicated by the adverb since, a prepositional phrase with since or a clause introduced by the conjunction since. e. g. â€Å"But, Dinny, when did you meet him? † â€Å"Only ten days ago, but I've seen him every day since. † The sun has been in the room since the morning. But she has seemed so much better since you started the injections. In the clause introduced by since the Past Indefinite is used to indicate the starting point of an action.However, we sometimes find in both parts of such complex sentences two parallel actions which began at the same time in the past and continue into the present. In this case the Present Perfect is used in both clauses, e. g. I've loved you since I've known you. It should be noted that the indication of time is indispensable to Present Perfect II because otherwise its meaning in most cases would be changed. It would come to denote an accomplished action which is part of the present situation. Cf. I've been taught to do it for three years. I have been taught to do it. But we met him here about a month ago.We haven't heard from him since. We haven't heard from him. Care should be taken to distinguish between the use of the Present Perfect and the Past Indefinite when the period of duration is expressed by a prepositional phrase with for. If the period of duration belongs to the past time sphere, the Past Indefinite should be used. It is only if the period of duration comes close to the moment of speaking or includes it that the Present Perfect is used. Cf. â€Å"I have lived like this,† he said, â€Å"for two years, and I can't stand it anymore. † â€Å"I teach History at a secondary school.I went to the University here for four years and got a degree. † The same is true of questions beginning with how long. â€Å"Are you married? † â€Å"Yes. † â€Å"How long have you been married? † â€Å"Are you married? † â€Å"No. I'm divorced. † â€Å"How long were you married? † 3) Present Perfect III is found in adverbial clauses of time introduced by the conjunctions when, before, after, as soon as, till and until where it is used to express a future action. It shows that the action of the subordinate clause will be accomplished before the action of the principal clause (which is usually expressed by the Future Indefinite).This use of the Present Perfect is structurally dependent as it is restricted only to the above mentioned type of clauses. e. g. â€Å"You'll find,† said Fred, â€Å"that you'll long for home when you have left it. † As soon as we have had some tea, Ann, we shall go to inspect your house. I'll take you back in my car but not till I've made you some coffee. Sometimes the Present Indefinite is found in this type of clauses in the same meaning as the Present Perfect. The choice of the form depends on the lexical meaning of the verb. With durative verbs the Present Perfect is necessary. e. g. When you have had your tea, we'll see about it.I can tell you whether the machine is good or bad when I have tried it. With terminative verbs the use of both forms is possible, Cf. He says when he retires he'll grow roses. When I've finished this I must go and put the baby to bed. Mother will stay at home until we return. â€Å"Your mother wouldn't like me. † â€Å"You can't possibly say that until you've met her. † 2. 2 Differences in Use of the Present Perfect in American and British English In British English the present perfect is used to express an action that has occurred in the recent past that has an effect on the present moment.For example: I've lost my key. Can you help me look for it? In American English the following is also possible: I lost my key. Can you help me look for it? In British English the above would be considered incorrect. However, both forms are generally accepted in standard American English. Other differences involving the use of the present perfect in British English and simple past in American English include already, just and yet. British English: I've just had lunch I've already seen that film Have you finished your homework yet? American English:I just had lunch OR I've just had lunch I've already seen that film OR I already saw that film. Have your finished your homework yet? OR Did you finish your homework yet? American English speakers do not use the present perfect for events that are still connected to the present. However, most Americans have a narrower perception of such connections than do other English speakers, particularly the British. For example, the British will say â€Å"have you had breakfast this morning,† but Americans will often say â€Å"did you have breakfast this morning. There is no difference in grammar; the difference is in the fact that Americans often think of the morning as being past history, whereas the British tend to see breakfast as still being part of the day, at least for a longer time than Americans do. Both groups use the past simple to describe things that they perceive to be unconnected with the present, and both groups use the present perfect to describe things that they perceive to be connected with the present. The difference is in the perception, not the grammar.Some Americans may well use the present perfect, if that's how they perceive the action in question. Conversely, some British speakers may use the past simple, if they think of the action in question as being isolated in the past. The important thing to remember is that, in many expressions, the choice between present perfect and past simple depends solely on what the speaker has in mind. If the speaker perceives something as being completely finished and unconnected to the present, he'll use the past simple; if he still sees some sort of connection to the present, he'll use the present perfect.Two different people talking about the exact same thing may choose to use two different tenses to describe it. There are some cases in which one tense or the other is gramatically necessary, of course, but there are many cases in which both are acceptable. If you specify a particular time in the past, for example, you normally use the past simple (â€Å"I did it yesterday†). And if you say â€Å"I've lived here for a year,† the implication is that you still live here, whereas if you say â€Å"I lived here for ayear,† the implication is that you no longer live here.Similarly, if a woman says â€Å"I've had two children,† things are going well, but if she says â€Å"I had two children,† it might be a good idea to change the subject. The distinction between present perfect and past simple is difficult to explain in terms of rules because the rules are quite complex. I usually explain it in terms of the speaker's perceptions and via specific examples that illustrate the different ways in which the tenses can be contrasted. If someone says â€Å"John went to the movie,† it tells me several things. It tells me that John is not with the speaker, for example.It implies that the speaker probably does not expect to encounter John while he is at the movie. It implies that nothing the speaker is doing right now is connected to John's trip to the movie. If someone says â€Å"John has gone to the movie,† that, too, tells me several things. It implies that John's trip to the movie is recent. It implies that something about John's action is connected to some present state or action in the speaker's mind (for example, she may be planning to join him, or she may be describing the reason for his absence in the present, as when answering the telephone).In many cases, the choice between the two is almost arbitrary. In isolation, the present perfect sounds more recent, and/or implies that something may have happened more than once in the past, and implies a connection with the present somehow, but in many contexts these distinctions are unimportant. If someone answers the phone and is asked about John, she wi ll probably say â€Å"He has gone to the movie,† but she might also very well say â€Å"He went to the movie,† particularly if she is American (Americans have a narrower perception of â€Å"present time† than do many other English speakers).Conclusion After investigation of the theme â€Å"The Present Perfect Tense† I came to the conclusion that although the perfect tenses are called as the secondary tenses in the works of Russian scientists Ganshina and Vasilevskaya, it appears to be one of the main and indispensable constituents of the English language tense form. Every action leads to the results. Without results the action is not valuable. So the essence of using the perfect tenses is in expressing the results, consequences and the level of accomplishment and duration of the action.The present perfect tense and its use follow the learners of the English language from the first stage of the learning and of a great importance on the same level as the ve rb ‘to be’ or there is/ there are constructions. So, on the basis of the theoretical and practical investigation of the use of perfect tenses in the works of prominent Russian and English scientists and within American and British fiction conforming to the examined theory, we have reached the following results of the research work: The Perfect form denotes an action completed before the present moment (and connected with it) or before a definite moment in the ast or future. It is formed by means of the auxiliary verb to have in the required tense and Participle II of the notional verb. The Present Perfect is used in the following cases: 1. The Present Perfect denotes a completed action connected with the present. 2. The Present Perfect is used in adverbial clauses of time after the conjunctions when, till, until, before, after, as soon as to denote an action completed before a definite moment in the future. 3. The Present Perfect denotes an action which began in the pas t, has been going on up to the present and is still going on.In this case either the starting point of the action is indicated or the whole period of duration. The preposition for is used to denote the whole period of duration. Since is used to indicate the starting point of the action. If the conjunction since introduces a clause, the verb in this clause is in the Past Indefinite. In British English the present perfect is used to express an action that has occurred in the recent past that has an effect on the present moment. For example: I've lost my key.In American English the following is also possible: I lost my key. In British English the above would be considered incorrect. However, both forms are generally accepted in standard American English. Other differences involving the use of the present perfect in British English and simple past in American English include already, just and yet. British English: I've just had lunch American English: I just had lunch OR I've just had l unch American English speakers do not use the present perfect for events that are still connected to the present.However, most Americans have a narrower perception of such connections than do other English speakers, particularly the British. Bibliography 1. ?. ?. , , , 1968, 227 . 2. ?. ?. , A Grammar of Present Day, ,  «Ã‚ »,1990, 100 . 3. Greenbaum Sidney, Oxford English Grammar, Oxford, Oxford University Press, 1996, 652 p. 4. Greenbaum Sidney, Quirk R. , Leech G. , Svartvik J, A University Grammar of English, Moscow, 1982, p. 158 5. Newsperson Otto, University of Grammar, Chicago and London, The

Timeline of the Algerian War of Independence

Here is a timeline of the Algerian War of Independence. It dates from the time of French colonization to the end of the Battle of Algiers. The Wars Origins in French Colonization of Algeria 1830 Algiers is occupied by France. 1839 Abd el-Kader declares war on the French after their meddling in the administration of his territory. 1847 Abd el-Kader surrenders. France finally subjugates Algeria. 1848 Algeria is recognized as an integral part of France. The colony is opened to European settlers. 1871 Colonization of Algeria increases in response to the loss of the Alsace-Lorraine region to the German Empire. 1936 Blum-Viollette reform is blocked by French Settlers. March 1937 The Parti du Peuple Algerien (PPA, Algerian Peoples Party) is formed by the veteran Algerian nationalist Messali Hadj. 1938 Ferhat Abbas forms the Union Populaire Algrienne (UPA, Algerian Popular Union). 1940 World War IIFall of France. 8 November 1942 Allied landings in Algeria and Morocco. May 1945 World War II Victory in Europe.Independence demonstrations in Stif turn violent. French authorities respond with severe reprisals leading to thousands of Muslim deaths. October 1946 The Mouvement pour le Triomphe des Liberts Dmocratiques (MTLD, Movement for the Triumph of Democratic Liberties) replaces the PPA, with Messali Hadj as president. 1947 The Organization Spciale (OS, Special Organization) is formed as a paramilitary arm of the MTLD. 20 September 1947 A new constitution for Algeria is established. All Algerian citizens are offered French citizenship (of equal status to those of France). However, when an Algerian National Assembly is convened it is skewed to settlers compared to indigenous Algerians -- two politically equal 60-member colleges are created, one representing the 1.5 million European settlers, the other for 9 million Algerian Muslims. 1949 Attack on the central post office of Oran by the Organization Spciale (OS, Special Organization). 1952 Several leaders of the Organization Spciale (OS, Special Organization) are arrested by French Authorities. Ahmed Ben Bella, however, manages to escape to Cairo. 1954 The Comit Rvolutionaire dUnit et dAction (CRUA, Revolutionary Committee for Unity and Action) is set up by several former members of the Organization Spciale (OS, Special Organization). They intend to lead the revolt against French rule. A conference in Switzerland by CRUA officials sets out the future administration of Algeria after the defeat of the French -- six administrative districts (Wilaya) under the command of a military chief are established. June 1954 New French government under the Parti Radical (Radical Party) and with Pierre Mends-France as chairman of the Council of Ministers, an acknowledged opponent of French colonialism, withdraws troops from Vietnam following the fall of Dien Bien Phu. This is seen by Algerians as a positive step towards recognition of independence movements in French-occupied territories.