The program browsing problem is discussed, with particular emphasis on a multiple-window user interface and its implications for recording acquired knowledge, navigation, and attention-tracking. Hypertext systems are considered as an implementation of b rowsing techniques for non-program text. A classification scheme for text-viewing systems is offered, and then browsing is discussed as a non-intrusive, static technique for program study. Multiple techniques are synthesized into a coherent plan for a multi-window program study tool, based on theories of program browsing and the use of hypertext. A test system, HYBROW, emerged from the plan for studying the application of several hypertex t multiple-window techniques to program browsing, especially window replacement. HYBROW is a hypertext, multiple-window program browser. This generic tool is applicable to any source language, although certain aspects of the preprocessing and the hierarc hical browser presentation are specific to the C language. The tool permits opening an arbitrary number of text windows into an arbitrary number of files, rapid window switching, multiple-window search, place-marking, automatic screen organization, and s ervices for the creation, maintenance and production of study notes. An informal usability study was conducted.