Digital inking systems are becoming increasingly popular across a variety of domains. In particular, many systems now allow instructors to write on digital surfaces in the classroom. Yet our understanding of how people actually use writing in these systems is limited. For an example, we report on classroom use of writing in one such system, in which the instructor annotates projected slides using a Tablet PC. Digital inking systems (computer applications that accept pen based written input) promise infinite malleability and detailed archiving of ink. Ink can change colors, be moved and resized and transformed into typeset text. Inking systems can record time, pressure, context, and other information for every stroke drawn. Digital ink technologies have evolved over time and include cameras, touch sensitive whiteboards, PDA's, Tablet PC's, and digital pens. Systems using these technologies support note taking and sharing, real-time distributed conversation and meetings and classroom presentation and capture.