English is a tool used for global communication in this era and students go to the school learning English as first-foreign language. English teacher uses English in explaining the material and sometimes switches their explanation into Indonesian. The reason why the researcher wants to conduct a research about English teacher’s code-switching is to find the frequency, functions, and possible factors of teacher’s code-switching in the classroom. Thus it is important to investigate the use of code-switching by teacher to get detail information above.
This study uses qualitative approach because the data are spoken. It was conducted at 10th grade of SMAN 7 Semarang in the academic year of 2010/2011. The researcher analyzes the use of teacher’s code-switching. The data collection are; observation and interview.
The result of the study shows that the details of code-switching used by the teacher. In English teaching learning process within 2x45 minutes, there are 111 utterances in the classroom which contains 72 (64.86%) which are pronounced by the English teacher. There are 6 functions of classroom code-switching from 72 utterances which are pronounced by the teacher: Insufficient vocabulary resources appeared one time (1.40%), affective function appeared one time (1.40%), emphasis appeared 37 times (51.40%), elaboration appeared eight times (11.10%), addressee specification appeared four times (5.50%) and clarification appeared 21 times (29.20%). From all functions, emphasis function is the dominant function that appeared 37 times (51.40%). The possible factors are: It’s natural phenomenon to code-switch English into Indonesian as the first language to overcome misconception or misunderstanding between the teacher and students, underscoring the material to improve students understanding in receiving the materials. The last, teacher sometimes code-switches the explanation without any problem which is occurred by teacher’s habit.