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Hercules Version 3: Frequently-Asked Questions

Posted in Hercules Soft on August 12, 2004

1.01 What is Hercules?

Hercules is a software implementation of the System/370, ESA/390 and z/Architecture mainframe architectures. Hercules runs under Windows and Linux, as well as under various other Unix or Unix-like systems on Intel Pentium and other hardware platforms including Alpha, Sparc, and Mac.

1.02 So what exactly does that mean?

It means that your PC can emulate an IBM mainframe processor. The mainframe can range from a System/360 to a z990 - running in "S/370" mode, "ESA/390" mode, or "z/Architecture" mode.

Hercules executes S/370, ESA/390, and z/Architecture instructions and channel programs. It emulates mainframe I/O devices by using PC devices. For example, 3390 DASD devices are emulated by large files on your hard disk, and local 3270 screens are emulated by tn3270 sessions. (Note: Not all 370 and 390 features have been implemented in Hercules. See the list of particulars later in this document. Also, certain non-standard models, 360/20s, and the 360/67 virtual memory mode are not emulated.)

Hercules implements only the raw S/370, ESA/390, and z/Architecture instruction set; it does not provide any operating system facilities. This means that you need to provide an operating system or standalone program which Hercules can load from an emulated disk or tape device. You will have to write the operating system or standalone program yourself, unless you can manage to obtain a license from IBM to run one of their operating systems on your PC, or use IBM programs and operating systems which have been placed in the public domain.

1.03 Is it functional enough to run production work?

Hercules has never claimed to be a production-capable system. It was always meant to be a system programmer's toy. Having said that, it's now become good enough to run a wide range of software without problems, and there are reports that it has been used to run production work in some parts of the world.

1.04 What are the licensing restrictions for Hercules?

Hercules is a copyright work which has been made generally available, subject to the terms of the Q Public License. In essence this allows free use and distribution of the program for personal and commercial use. You may not distribute modified copies of the program, but you may distribute your own patches along with the program, provided that you also grant the maintainer permission to include those patches in future versions of the program. You may not copy any portion of the source code for use in any other program.

Hercules is not, repeat, not GPL software! The GNU General Public License is a Unix/Linux software licensing agreement, which we, the authors, will not participate in. We believe that the QPL, which has been certified as compliant with the Open Source Definition, provides the benefits and protections of open source for both users and developers, without the political baggage that has come to be associated with the GPL.

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