Code switching is language behaviour in bilingual or multilingual society as in Indonesia. It is common to be used in the school and Islamic boarding house, especially bilingual school. One of the multilingual Islamic boarding house is Pondok Pesantren Darul Falah Be-Songo Semarang. The students who also students in Walisongo State Islamic University, should use three languages: Kromo Inggil, Arabic, English. They are divided in a month. First week for English, second week for Arabic and Kromo Inggil in every Saturday and Sunday. By the background differentiation of students’, English, especially, is not spoken fluently by the students. So they use English and Indonesian as combination. The researcher thinks that it is interested to analyze the code switching in their daily speaking. The objectives of this study are to find out (1) the reasons of code switching used in Pondok Pesantren Darul Falah Be-Songo Semarang, and (2) the types of code switching the students used. This research was descriptive qualitative research. The researcher used triangulation. In this case, she used interview and observation to get the data about code switching the students used in Pondok Pesantren Darul Falah Be-Songo Semarang. This research used Hoffman and Dias opinion to analyze the reasons of code switching. They are: talking about particular topic, quoting somebody else, being emphatic about something, interjection, repetition, intention, expressing group identity, soften/strengthen request/command, because of real lexical
 
need and to exclude other people. Thus, the researcher used Hoffman opinion in classifying the types of code switching including Intra Sentential Switching, Inter Sentential Switching and Tag Switching. The researcher found six of ten reasons are usually used by students. The four left are seldom or even never been used because of the students’ language native is Indonesian. So, those reasons are not suitable. Whereas, the three types of code switching were all used by students. The mostly types the students used is inter sentential switching.