2.3 Studies on code-switching in classroom discourse

Many researchers have made efforts to explore the types of code-switching from different perspectives of structure or function. Because of different research approaches and their research goals, different researchers have distinguished different types and functions of code-switching. 

2.3.1 Types of code-switching

The most classic and popular classification is made by Poplack (1980) who has successfully differentiated three types of code-switching：inter-sentential code-switching, intra-sentential code-switching and tag code-switching according to where switches occur within sentences. Later he developed another distinction between "smooth switching" and "flagged switching" (Poplack, 2007). The former is also known as skilled or fluent code-switching while the latter implies that there isn't such smoothness, and switching may be marked by some attributes.

2.3.2 Functions of code-switching

Many researches have focused on the functions of classroom code-switching. For example, Piasecka (1988) discussed the use of students, native language in ESL classes in Poland. She suggests that code-witching should be a joint decision between teachers and students. She makes a suggestion that code-switching in the classroom gives learners some opportunity to learn the social values behind each code and to be aware of how to negotiate their identities by this kind of language alternation. 

 Some researchers describe how code-switching can serve some social functions in classroom. For example, Canagarajah (1995) examined the use of code-switching by secondary school teachers in English L2 classrooms in Jaffna, Srilanka. Although the use of Tamil is considered inappropriate for English second language classroom, this study reveals some different kinds of functions for both teachers and students, such as giving instructions, managing discipline, giving commands, reviewing lesson content and requesting help. She argued that English, as an L2, was used primarily for class interaction strictly related to the lesson content, but Tamil, the students' native language, was used for all other interactions, including those that were personal or unofficial in nature. She makes a suggestion that code-switching in the classroom gives learners some opportunity to learn the social values behind each code and to be aware of how to negotiate their identities by this kind of language alternation.

Liu Jingxia (2010) states the functions of code-switching in Chinese classrooms. She says the functions of code-switching are: translation of unfamiliar words, explanation of grammar, managing class, helping students apprehending difficulties and indicating sympathy and friendship to students, putting stress on important notions, citing sayings of others, shifting topics, getting students' concentration, assessing the understanding, etc.