Amazon.com description: Product Description: Interchange Fourth Edition is a four-level series for adult and young-adult learners of English from the beginning to the high-intermediate level. For those students who prefer to study and practice from their personal computers, a downloadable Digital Student's Book for each level of Interchange Fourth Edition provides them with digital tools and the same great content. Interchange Fourth Edition DigiBook Intro level features the Student's Book in digital format with full class audio, full class video, audio and video scripts for further support, and corresponding Video Activity Worksheets. Pen tools allow students to highlight, mark, note, and draw. Interchange Fourth Edition DigiBook also allows students to save notes, marks, highlights, and bookmarks between sessions.