Xv6

xv6 is a modern reimplementation of Sixth Edition Unix in ANSI C for multiprocessor x86 and RISC-V systems. It was created for pedagogical purposes in MIT's Operating System Engineering course in 2006.

Purpose
MIT's Operating System Engineering course formerly used the original V6 source code. xv6 was created as a modern replacement, because PDP-11 machines are not widely available and the original operating system was written in archaic pre-ANSI C. Unlike Linux or BSD, xv6 is simple enough to cover in a semester, yet still contains the important concepts and organization of Unix.

Self-documentation
One feature of the Makefile for xv6 is the option to produce a PDF of the entire source code listing in a readable format. The entire printout is only 99 pages, including cross references. This is reminiscent of the original V6 source code, which was published in a similar form in Lions' Commentary on UNIX 6th Edition, with Source Code.

Educational use
xv6 has been used in operating systems courses at many universities, including:
 * Adolfo Ibanez University
 * Ben-Gurion University
 * Binghamton University
 * CentraleSupélec
 * Columbia University
 * Ghulam Ishaq Khan Institute
 * Federico Santa María Technical University
 * George Washington University
 * Nile University
 * Georgia Tech
 * IIIT Allahabad
 * IIT Bhubaneswar and PEC Chandigarh
 * IIT Bombay
 * IIT Delhi
 * IIT Madras
 * IIIT Delhi
 * IIIT Bangalore
 * IIIT Hyderabad
 * Iran University of Science and Technology
 * Johns Hopkins University
 * Karlsruhe Institute of Technology
 * Linnaeus University
 * Milwaukee School of Engineering
 * Motilal Nehru National Institute of Technology Allahabad
 * National Taiwan University
 * National University of Córdoba
 * National University of Río Cuarto
 * New York University
 * Northeastern University
 * Northwestern University
 * Portland State University
 * Rutgers University
 * Slovak University of Technology in Bratislava
 * Southern Adventist University
 * Stony Brook University
 * Technion – Israel Institute of Technology
 * Télécom SudParis
 * Tsinghua University
 * Federal University of Minas Gerais
 * University College Dublin
 * University of Belgrade School of Electrical Engineering
 * University of California, Irvine
 * University of California, Riverside
 * University of Hyderabad
 * University of Illinois at Chicago
 * University of Leeds
 * University of Modena and Reggio Emilia
 * University of Otago
 * University of Palermo
 * University of Pittsburgh
 * University of Strasbourg
 * University of South Florida
 * University of Tehran
 * University of Utah
 * University of Virginia
 * University of Wisconsin–Madison
 * University of Kassel
 * Yale University