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Burroughs B5500 Mark XIII Release ZIP Archive

The archive file contains the source and object code for the entire Mark XIII release of late 1971, translated from 6-bit B5500 internal code to ASCII, using the standard retro-b5500 substitutions for the B5500 characters that do not have ASCII equivalents. The download .zip file size is 5.2MiB, expanding to 28.2MiB.

The files converted from the tape images are in standard Windows text format (CR-LF delimiters), but their file names do not have extensions. They can be opened in any text editor than can handle ASCII with CR-LF delimiters.

Note that the object code is not usable in this representation, but since all 6-bit B5500 codes have printable ASCII glyphs, the object code is in what amounts to a specialized base-64 encoding.

License to Use the Archive Contents

Unisys Corporation, the successor to Burroughs, retains ownership of and copyright to the content of this data. We have entered into a license agreement with Unisys to use this content with our project for non-commercial purposes, and to make this content available to others under the terms of that agreement. You can read the full text of the agreement here.

In order to download the tape image you must abide by the terms of that agreement, and in particular, the terms of its Section 2, below. Your specific obligations are set forth in paragraph 2.3(d). Note that the agreement does not have a paragraph 2.3(c).

2.1 UNISYS hereby grants LICENSEE a personal, internal to LICENSEE only, non-exclusive, fully-paid right and license, including the right to sublicense for use and to copy (only to the extent reasonably necessary for LICENSEE to make and support Derivative Works), compile, modify, enhance and create Derivative Works of the Program and Program Materials solely for LICENSEE's non-commercial educational or hobbyist purposes, internal use and internal support.
2.2 LICENSEE shall reproduce all confidentiality notices, copyright notices, limited rights legends, restricted rights legends and other proprietary rights notices contained within the Source Code.
2.3 UNISYS hereby authorizes LICENSEE to do the following with the Program and Program Materials solely for non-commercial educational or hobbyist purposes:
(a) Preserve the Program by (i) storing the Program in different formats; (ii) copying the Program onto stable media as needed; and (iii) tagging the Program with metadata for easy identification and classification.
(b) Allow the Program to be run in simulators, or actual hardware.
(d) Provide the Program and Program Materials to private individuals ("LICENSEE Users"), wherein the LICENSEE Users will be subject to the responsibilities set forth in Section 2.2 and enjoy the rights granted in Sections 2.1, 2.3(a) and 2.3(b). LICENSEE will not authorize or encourage LICENSEE Users to remove confidentiality notices, copyright notices, limited rights legends, restricted rights legends and other proprietary rights notices contained within the Programs and Program Materials to which they have access.
2.4 UNISYS has no obligation to deliver the Program or Program Materials to LICENSEE; LICENSEE must collect the materials through its own resources.

To download the archive file, please check the box below confirming your acceptance of the terms of the license and your obligations thereunder, then click the Download button.


If you choose not to agree, then please return to the Mark XIII System Software page.

Contents of the B5500-XIII-Release archive file

A directory of the files is included as Mark-XIII.dir.txt; a dump of the file headers from the original tape images is included as Mark-XIII.tape-dir.txt.


Copyright (c) 2013, Nigel Williams and Paul Kimpel • Licensed under the MIT License
Revised 2017-05-28