As to the definitions above, CI in this research is a language used by teachers for teaching and organization。 It is used to direct students’ behavior, to explain the activities so that students can get well involved in the class and to connect the exchange in the class。 There are two main types of instructions according to the related study。 The first type is concrete, which emphasizes the directive means, like the instructions of using a fridge。 Another type is simple, which emphasizes on the target。 For instance, if I want someone to close the door, I just need to give him/her the instruction ‘close the door please’。 So the former type aims at explaining the procedures of a task while the latter one aims at directing actions。

2。2 The study of Chinese and western scholars on classroom instructions

 Classroom is an essential part of English learning in middle school。 Classroom instruction is the language which teachers use to organize and manage the EFL classrooms and implement their teaching plans。 It is a way by which the teacher expresses his/her opinions, achieves teaching target and builds a bridge between teaching and learning for the students, and therefore, is closely associated with communicative language teachings。 As a significant part of teacher talk, it is also the most important source of student's input and teachers’ behavior。 

There have been many scholars who have studied classroom instruction both at home and abroad。 Firstly about the principles of giving instructions, in order to give effective CI, some scholars have proposed several guidelines。 Parrot (1994) gave four principles for giving effective CI。

(1) Prepare instructions very carefully at the lesson-planning stage in order to ensure that they are clear in the target language。

(2) If the teacher is worried about the class understanding his instructions or explanation, he can ask a student to translate what he has said to the others。

(3) Use the students' first language when there is an obvious breakdown, in communication of the instructions。

(4) The giving of instructions provides one of the few opportunities for genuine communication in the classroom。

Parrot assumed that it is significant for teachers to prepare instructions which should be clear and understandable for students before class。 Harmer (1998) put forward the ideas that firstly CI should be as simple as possible。 Secondly, they must be logical。 Ur (1996) also proposed some main rule of giving effective instruction in the ESL classroom。

(1)  Prepare: It is worth preparing, thinking for a while about the words you will use, the illustrations you will provide, and so on; possibly even writing these out。

(2)  Make sure you have the class full attention。

(3) Present the information more than once。 Learners' attention wanders occasionally, and it is important to give them more than one chance to understand what they have to do。

(4)  Be brief。 Make your explanation as brief as you can。

(5)  Frustrate with examples。

(6)  Get feedback。 When you have finished explaining, check with your class that they have understood。 

                                                          (Ur 1996:16-17)

Similar to Parrott, Ur emphasized the significance of preparation and feedback。 He assumed that teacher should prepare effective CI before class。 And in order that the CI can be well understood, teachers can get information by interacting with students。 Parrott didn't explain how to give effective instruction while Ur proposed three rules-repetition, briefness and example illustration on this aspect。 So far, there have been many guidelines of CI from many different aspects (length, clarity, coherence and etc。)。 To sum up, the key of these principles is for making CI easier to understand by students。