Info (Unix)

Info is a software utility which forms a hypertextual, multipage documentation and help viewer working on a command line interface.
Info reads "info" files generated by the "texinfo" program and presents the documentation as a tree with simple commands to traverse the tree and to follow cross references. For instance, pressing the space bar scrolls down within the current tree node or goes to the next node in the current document if already at the bottom of the current node, allowing to read the contents of an info file sequentially. Pressing the backspace key moves in the opposite direction. Furthermore:
The C implementation of info was designed as the main documentation system of GNU based Operating Systems and was then ported to other Unix-like operating systems. However, info files had already been in use on ITS emacs. On the TOPS-20 operating system INFO was called XINFO.