Penelitian ini meneliti penggunaan campur kode dalam Twitter di kalangan mahasiswa Sastra Inggris angkatan 2010 Universitas Indonesia yang cenderung melakukan code mixing dalam percakapan sehari-hari karena terbiasa menggunakan bahasa Inggris di lingkungan perkuliahan sehari-hari. Namun, fokus penelitian ini adalah komunikasi tertulis pada akun Twitter mereka. Penelitian ini memiliki dua poin utama. Pertama, penjelasan tentang code switching itu sendiri berdasarkan teori “Reasons for Bilinguals to Switch or Mix their Languanges” dari Hoffman (1991). Kedua, alasan mengapa mahasiswa melakukan code switching pada akun sosial media mereka, seperti Twitter. Metode deskriptif kualitatif digunakan untuk menganalisis data yang dikumpulkan dari tweet sepuluh responden yang merupakan mahasiswa Sastra Inggris angkatan 2010 Universitas Indonesia. Selanjutnya, responden diwawancara terkait penggunaan campur. Hasil dari penelitian ini menujukkan bahwa terdapat enam alasan penggunaan campur kode, yaitu talking about a particular topic, quoting somebody else, being emphatic about something, interjection (Inserting sentence fillers or sentence connectors), pride and limited Words or Unknown Translation. Akan tetapi, persentase penggunaan campur kode yang paling tinggi digunakan adalah interjection karena menurut responden, mereka dapat menunjukkan perilaku bahasa ini sengaja atau tidak sengaja dalam komunikasi tertulis untuk mengungkapkan perasaan mereka.

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This paper examines the use of code mixing in Twitter among students of English Studies 2010 at Universitas Indonesia who tend to do code mixing in their daily conversation since they are used to speak English every day in their courses. However, this research focuses more on written communication in their Twitter account. There are two major points that this paper attempts to make. First, the description of code mixing itself according to the theory “Reasons for Bilinguals to Switch or Mix their Languages” given by Hoffman (1991). Second, the reasons why those students use code mixing in their media social account, such as Twitter. In order to get the result, descriptive qualitative method is used to analyzed the data from the twitter account of ten students of English studies 2010 at Universitas Indonesia. Moreover, a structured interview regarding the code mixing practised was conducted. The results of this research indicate that code mixing occurs among students for six reasons: talking about a particular topic, quoting somebody else, being emphatic about something, interjection (inserting sentence fillers or sentence connectors), indicating pride and limited words or not knowing the equivalent word in Indonesian language. However, the most common practice is of code mixing is the use of interjection because according to the respondents, they may show this language behavior accidentally or intentionally in written communication to express their feelings.