The book is a comprehensive study of English lexical borrowings in informal Polish of computer science. The research is based on a corpus of texts compiled by the author. The monograph contains a detailed description of 548 English loanwords. The book also includes an extensive theoretical discussion of lexical loans, as well as a description of the problems related to their identification and differentiation from other types of borrowings. The book is addressed to researchers interested in language contact and English borrowings, as well as the language of computer science. It may also be of interest to practitioners, translators, and all those who want to better understand the contemporary Polish language of computer science.