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Sim390 is an application that runs under Windows and emulates a subset of the ESA/390 mainframe architecture. The emulator supports most TCP/IP operations (via socket calls using an emulated IUCV interface), and contains a Telnet 3270 (tn3270) server for remote log-in (with IP address filtering), as well as local 3270 sessions. Sim390 has been tested under Windows 95, 98, NT, 2000, and XP. It is very easy to install. It is possible to run it on a very small machine such as a Pentium 75 MHz with 16 MB memory (Windows 95).

For a 1-volume demo operating system that can be IPL'd and run under Sim390, download the file referred to on the download page. Use WinZip to unzip the file to a new directory c:\sim390dm on your Windows machine, and read the instructions in the readme file.

The operating system contained in the .zip file is MUSIC/SP, which stands for Multi-User System for Interactive Computing / System Product. It has a nice 3270 full-screen editor, TCP/IP utilities (Web server, FTP client and server, etc.), and VSAM. The MUSIC/SP demo system can also run under the Hercules emulator. Programming languages available for the demo system include: Assembler, Fortran G, PL/1 (F), Basic, Rexx, GCCMVS C, Assist, Stanford Pascal, Watfiv, Watbol, and Waterloo C. There is a sockets API for Waterloo C, which lets you write TCP/IP applications in C and run them under MUSIC/SP.

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This software, including the Sim390 mainframe emulator, the MUSIC/SP Demo system, and third-party software provided with the MUSIC/SP Demo system, is provided on an "as-is" basis, and is intended only for demonstration and evaluation purposes. Use it at your own risk. The author is not responsible for any damages or losses that may occur from your use of this software, and no support or warranty is provided. This software must not be used, sold, or distributed for profit, without the written permission of the author. It is provided only for personal use by individuals. Use in a production or commercial or institutional environment is prohibited, unless specific written permission is obtained from the author.

Sim390 is © Copyright by Dave Edwards, 2001-2008. All rights reserved.

The MUSIC/SP operating system is © Copyright by McGill University, 1989-2000. Additions and modifications to MUSIC/SP and its components made 2001 and later, as distributed with the MUSIC/SP Demo system, are © Copyright by Dave Edwards, 2001-2008.

Known Problems

See the bugs page for a list of known problems and fixes.

Sample Screens

See the screens page for some sample screen shots of Sim390 and MUSIC/SP in action.

Latest News

Feb 26, 2008 - Sim390 version 1.7
Version 1.7 of Sim390 is now available for download. It has improvements to the user interface, a new HTML help file, support for changing the font in local 3270 sessions, better and more complete emulation of floating-point instructions, and a minor bug fix for the IPM instruction.

Jan 31, 2008 - Recent updates for MUSIC/SP
The following updates to the MUSIC/SP 6.2 Demo system are available: - GCCMVS C compiler (replaces - Various nucleus updates and other additions. Includes support for high-memory areas and 31-bit address mode.

Aug 24, 2007 - Update for MUSIC/SP, including Fortran G fixes
Update is available for download. It fixes some problems in the Fortran G interface, updates the MUSIC/SP nucleus (mainly to support file creation time-of-day in addition to creation date), and adds several commands, utility programs, and Help and documentation files. Please note that previous updates upd1, upd2, and fortg are prerequisites for upd3.

Jul 16, 2007 - Updates for the MUSIC/SP Demo system
Recent updates available for download: - Mods to HTTPD, WEB, FTPD, MFCHEK. - Stanford Pascal compiler. - GCCMVS C compiler for MUSIC/SP, version 1.0. - Fortran G compiler and library; delink utilities.

Dec 19, 2006 - Recent updates for the MUSIC/SP Demo system
Recent updates include: (Univ. of Waterloo's Cobol compiler), (updates and additions to Demo system components, including ftpd), (Penn State Univ.'s S/360 assembler and execution environment, contributed by Mike Short). Follow the link on the download page.

Sep 28, 2006 - Sim390 version 1.6
Version 1.6 of the Sim390 emulator is available. Get it from the download page. This version has support for tn5250 telnet clients. Sim390 acts as a tn5250 server, which allows a tn5250 client to log in to the MUSIC/SP system. Sim390 translates between 5250 and 3270 terminal data streams, so that MUSIC/SP thinks it is talking to a 3270, while the tn5250 client thinks it is talking to a 5250 server such as an IBM AS/400 or iSeries midrange computer. This is useful for testing tn5250 clients. Sim390 has been tested successfully with several tn5250 clients. Not all features of 5250 terminals are supported. For more info on 5250, see info5250.txt on the Tech Info page.

Sep 20, 2006 - New add-on packages for the MUSIC/SP Demo system
Two 360-era add-on packages, contributed by Mike Short, are now available for the Demo system. File has a program that converts Fortran source to PL/1 (F). has SSP (Scientific Subroutine Package), single-precision version with PL/1 (F) source. See the download page.

Jun 30, 2006 - MUSIC/SP Demo system, version 6.2
The Demo system has been repackaged as version 6.2. You can download it as file - see the download page. It has all the 6.1 updates already applied, and its Save Library and Load Library have been expanded.
Note: The previous updates for version 6.1 must NOT be applied to the new 6.2 Demo system.

Jun 16, 2006 - Demo system update misc11.arc
Update misc11.arc is now available for the MUSIC/SP 6.1 Demo system. Highlights include the ability to use VSAM files from programs written in PL1/F, and tcp/ip socket programming from Rexx.
Note: This and the other updates for version 6.1 must NOT be applied to the new 6.2 Demo system (, since they are already part of the 6.2 system.

Apr 7, 2006 - Demo system update misc10.arc
Update misc10.arc is now available for the MUSIC/SP 6.1 Demo system. Highlights include the ability to use VSAM files from within Rexx programs, and a CGI program that supports HTML form-based file upload (RFC 1867). See the readme.txt file there for details. VSAM (Virtual Storage Access Method) is a mainframe data storage method that can access records by a key field which is stored in an index; it is very efficient for direct access to a large number of records.

Feb 9, 2006 - MUSIC/SP update available: misc9.arc
This update to the MUSIC/SP 6.1 Demo system provides improvements to the web server HTTPD, including limited support for a variation of Digest authentication for web documents and CGI's, and several other new programs and files. Also, several new files have been added to the Tech Info page. There is a new PC program httpput.exe which uploads a file to a web server using an HTTP PUT request.

Dec 3, 2005 - Some Linux programs added
Some small Unix/Linux utility programs are available for download. These include a Linux version of the wipezero command, which can be used to enlarge a Sim390 or Hercules FBA volume file. Some C source is provided.

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