A calculator having a hierarchical tree view (HTV) window provides a more efficient method of displaying calculator usage history. The HTV window provides tabs to choose between multiple windows displaying usage history such that more information can be displayed quickly without using more display area than is necessary. The HTV window also provides a view of usage such that expressions listed in the HTV window can quickly be expanded or unexpanded by the user in order to see data associated with that expression. Tool tip information may be provided to the user, displayed expressions may be re-used by double-clicking or dragging and dropping operations, expressions may be grouped into user-defined folders, and symbols may be used for easy identification of expressions, results, or folders. Additionally, usage history may be stored into a file, files may be opened for the purpose of re-using such usage history at a subsequent time, and scripts and functions may be created, executed, and saved for subsequent use.