Whyteboard allows you to annotate PDF and PostScript documents and various image formats. You can draw with common tools such as a pen, rectangle, ellipse, text tool, etc. You can draw shapes, which can be moved, resized, recoloured, etc. Your drawing history is stored, allowing you to replay it. Tabbed painting is supported, with each sheet having its own unlimited undo and redo operations. There are live-updating thumbnails for each sheet. Sheets that are closed can also be undone, restoring their data. Note controls, similar to virtual, editable Post-It Notes. A draggable, live-updating resizable canvas that stretches to whatever size you want.
Bitcoin is a peer-to-peer electronic cash system that is completely decentralized, without the need for a central server or trusted parties. Users hold the crypto keys to their own money and transact directly with each other, with the help of a P2P network to check for double-spending.