The build system compiles this code into an ISO file that can be mounted as a VM's virtual CD-ROM drive, as described in the user manual. Src/VBox/HostServices/: src/VBox/Installer/: The code for the Linux and Windows installes, in their respective subdirectories. For Linux, we use some shell scripts glued together with a tarball, for Windows. Source code folder; VrApi: The Virtual Reality API provides a minimal set of entry points for enabling VR rendering in native applications and third-party engines. VrApi: VrApi Includes: Header files for the VrApi library. VrApi/Includes: Native Samples: Sample projects illustrating use of VrApi.
Development and License Agreement
Last updated: 08.09.2020
This Development and License Agreement is a non-exclusive Agreement between __________ (the Customer) and Rais Garifullin (hereinafter mentioned as Contractor).
Two Pilots is Rais Garifullin's trade mark.
1. Subject
Virtual Source Code
The subject of the present Agreement is Custom Virtual Printer Driver hereinafter mentioned as Software, Software source code hereinafter mentioned as Source Code including the whole delivery package, namely the software itself and the covering documentation.
2. Accepting or Rejecting the Agreement
Any usage of this product including installation of the Software and Source Code or any of theirs parts on a computer, loading the product into operating memory (RAM) or permanent storage on a computer's disk or other storage medium, as well as any other type of usage means that you accept all the terms and conditions of the present Agreement. If you do not agree with any statement of this License, you should promptly terminate usage of the product and delete all the files referred to it, as its components, so as the results of its work, from your computer. You should also return all the existing mediums containing the Software and Source Code to the place where you obtained it.
3. Scope
Contractor agrees to develop and deliver the required Software according to following specification:
- Virtual Printer Driver for Windows XP/2003/2008R2/2012/Vista/7/8/8.1/10 including x64 versions.
Contractor agrees to develop and deliver the required Source Code according to following specification:
- Source code of base EMF virtual printer driver for Windows XP/2003/2008R2/2012/Vista/7/8/8.1/10 including x64 versions.
- Source code of other features and modules listed in the preceding specification of Software excluding the source code of PDF converter used in the PDF output format. This feature is provided as binary DLL used from the virtual printer source code and can be distributed along with the Software.
4. Price
Virtual Machine Source Code
The fixed price for the Software and Source Code is 9950 EUR.
5. Payments and Delivery
- Step 1. The Customer pays 9950 EUR.
- Step 2. Contractor delivers the Software and Source Code within six (6) business days after payment is received.
6. Copyright
The copyright of the Software and Source Code is owned by Contractor. The Software and Source Code is protected by Russian Federation copyright laws, international treaties and all other applicable national or international laws.
7. Licensing and Usage
Contractor grants Customer a royalty-free right to distribute the Software with applications Customer has developed. The Software may not be distributed for any other purpose than to accompany applications that Customer has developed. Customer may use the Software in Customer's specific purpose application programs, in which case Contractor grants Customer permission to use, give away or sell such programs in any country without additional license fees, as long as all copies of these programs bear a valid copyright notice and provided that Customer's product is not a development tool or library which includes only all or a portion of the Software. This permission is granted solely for the purpose set forth above, and Customer is not authorized to use the Software in any other manner.
Contractor permits Customer to modify Software Source Code.
Contractor does not authorize Customer to distribute the original or modified Source Code.
Software Source Code is trade secret. It is confidential and cannot be published in any format or media without prior written consent of Contractor.
Contractor prohibits Customer to create a competitive development services using the Source Code. Better ms paint.
8. Time Restriction
This product has no time limits in terms of its usage.
9. Limited Warranty
Contractor makes no warranties or representations, express or implied, in fact or law, including the implied warranties of merchantability and fitness for a particular purpose. Contractor does not warrant that the operation of Software will be uninterrupted or error free. Customer agrees that all warranties are immediately null and void in the event of modification or alteration of Software and Source code.
10. Limitation of Liability
Notwithstanding the form (e.g. contract, negligence, or otherwise) in which any legal or equitable action may be brought against Contractor, Contractor will not be liable for damages which exceed the amount of the license fees paid by the Customer for the Software. In no event will Contractor be liable for any damages, whether arising from tort or contract, including loss of data, lost profits, cost of cover, or other special, incidental, consequential, or indirect damages arising out of the use or inability to use the Software or accompanying documentation, however caused and on any theory of liability. This limitation will apply even if Contractor has been advised of the possibility of such damage. The Customer acknowledges that the license fee reflects this allocation of risk.
11. Miscellaneous
This Agreement represents the complete agreement concerning this license between the parties and supersedes all prior agreements and representations between them. It may be amended only by a writing executed by both parties. This Agreement shall be governed by and construed under Russian Federation laws.
12. Contractor
Two Pilots
Web site: https://www.colorpilot.com
13. Data details of the parties
(this part of the Agreement is to be filled out by Customer and Contractor at the time of making contract)
2. Introduction
In this tutorial, I will teach you how to write your own virtual machine (VM) that can run assembly language programs, such as my friend's 2048 or my Roguelike. If you know how to program, but would like to gain a deeper understanding of what is going on inside a computer and better understand how programming languages work, then this project is for you. Writing your own VM may sound a little scary, but I promise that you will find it to be surprisingly simple and enlightening.
The final code is about 250 lines of C (unix, windows).All you need to know is how to read basic C or C++ and how to do binary arithmetic.
Note: This VM is a literate program. This means you are reading the source code right now! Each piece of code from the project will be shown and explained thoroughly, so you can be sure nothing is left out. The final code was created by 'weaving' the blocks of code together.
What is a virtual machine?
A VM is a program that acts like a computer. It simulates a CPU along with a few other hardware components, allowing it to perform arithmetic, read and write to memory, and interact with I/O devices, just like a physical computer. Most importantly, it can understand a machine language which you can use to program it.
The amount of computer hardware the VM attempts to simulate depends on its purpose. Some VMs are designed to reproduce the behavior of some particular computer, such as video game emulators. Most people don't have an NES lying around anymore, but we can still play NES games by simulating the NES hardware in a program. These emulators must faithfully recreate every detail and major hardware component of the original device.
Other VMs don't act like any real computer and are entirely made up! This is primarily done to make software development easier. Imagine you wanted to create a program that ran on multiple computer architectures. A VM could offer a standard platform which provided portability for all of them. Instead of rewriting a program in different dialects of assembly for each CPU architecture, you would only need to write the small VM program in each assembly language. Each program would then be written only once in the VM's assembly language.
Note: A compiler solves a similar problem by compiling a standard high-level language to several CPU architectures. A VM creates one standard CPU architecture which is simulated on various hardware devices. One advantage of a compiler is that it has no runtime overhead while a VM does. Even though compilers do a pretty good job, writing a new one that targets multiple platforms is very difficult, so VMs are still helpful here. In practice, VMs and compilers are mixed at various levels.
Java Virtual Machine Source Code
The Java Virtual Machine (JVM) is a very successful example. The JVM itself is a moderately sized program that is small enough for one programmer to understand. This has made it possible to be written for thousands of devices including phones. Once the JVM is implemented on a new device, any Java, Kotlin, or Clojure program ever written can run on it without modification. The only cost is the overhead of the VM itself and the further abstraction from the machine. Most of the time, this is a pretty good tradeoff.
A VM doesn't have to be large or pervasive to provide a similar benefit. Old video games often used small VMs to provide simple scripting systems.
VMs are also useful for executing code in a secure or isolated way. One application of this is garbage collection. There is no trivial way to implement automatic garbage collection on top of C or C++ since a program cannot see its own stack or variables. However, a VM is 'outside' the program it is running and can observe all of the memory references on the stack.
Another example of this behavior is demonstrated by Ethereum smart contracts. Smart contracts are small programs which are executed by each validating node in the blockchain network. This requires the node operators to run programs on their machines that have been written by complete strangers, without any opportunity to scrutinize them beforehand. To prevent a contract from doing malicious things, they are run inside a VM that has no access to the file system, network, disc, etc. Ethereum is also a good application of the portability features that result when using a VM. Since Ethereum nodes can be run on many kinds of computers and operating systems, the use of a VM allows smart contracts to be written without any consideration of the many platforms they run on.
