#operating systems
An interrupt signals the occurrence of an event the kernel should be aware of. Hardware can trigger an interrupt at any time by sending a signal to the CPU, usually through the system bus; software can trigger an interrupt by executing a system call (also called a monitor call). When an interrupt occurs, the CPU stops what it is doing and transfers execution to a fixed location, which usually contains the starting address where the service routine for the interrupt is located. After the routine finishes, the CPU resumes what was interrupted.
Interrupts are an important part of a computer’s architecture. They transfer control to the appropriate interrupt service routine, which is usually defined in an interrupt vector, or array holding the addresses of interrupt service routines for various devices. Modern operating systems are interrupt driven, and events are almost always signaled by the occurrence of an interrupt or a trap.
Atrap, or an exception, is a software-generated interrupt caused either by an error (division by zero, segmentation fault, etc.) or by a request from the user program for an operating system service.
In x86, the IDT (interrupt descriptor table) provides pointers to interrupt and exception routines.
An operating system is software that manages the computer hardware and provides common services to user programs. They provide an environment in which a user can easily interface with the computer. Operating systems vary widely and often have different goals (mainframe operating systems versus PC operating systems versus real-time…).
A computer system can be divided into the hardware, the operating system, the application programs, and the users. The hardware (CPU, memory, I/O devices) provides basic computing resources. The application programs uses those resources to solve users’ computing problems. The operating system coordinates the use of resources.
A general-purpose computer system usually consists of one or more CPUs and a number of device controllers connected through a common bus that provides access to shared memory. The CPU and device controllers can execute concurrently - thus, a memory controller is provided to ensure orderly access to the shared memory.
A computer must have a bootstrap program, an initial program to run when the computer is powered up or rebooted. This firmware is typically stored in ROM (read-only memory) or EEPROM (electrically erasable programmable read-only memory). It initializes the system - CPU registers, device controllers, memory contents, etc. It also locates and loads the operating system kernel, which is the main component of the operating system.
Which operating system do you use on your machine? Odds are good it’s a version of Windows, according to this video-based chart that covers a 16-year period. Mac and Linux have strong minorities on the market.
Okay so like. There are developers who happen to develop for the web. They’re basically fine. And then there are Web Developers. And frankly I really admire the bravery and patience of developers who develop for the web for daring to dive into the cesspool created and maintained by Web Developers
And tbh I don’t wanna rag on Web Developers too much. They’ve been dealt an unfair hand in that the most visible, accessible, and influential sector of software development is constructed on the shittiest possible foundations, and is restricted to poorly made tools that structurally encourage the worst development practices in history. They, along with the rest of us, are haunted by the original sin of the First Web Developers, Brendan Eich and Rasmus Lerdorf
lmao if you think web foundations are bad just wait til you see everything else
In the beginning Brian Kernighan created C, and he saw that it was good.
see what i mean
C is bad but at least (a) it forces you to have some understanding of how computers work in order to use it at all and (b) we have other options now. Web development has no such saving grace
C is so bad that web development was created as an alternative to it.
The indented, italicized sections below appear as annotations to the Open Source Definition (OSD) and are not a part of the OSD. A plain version of the OSD without annotations can be found here.
Introduction
Open source doesn’t just mean access to the source code. The distribution terms of open-source software must comply with the following criteria:
1. Free Redistribution
The license shall not restrict any party from selling or giving away the software as a component of an aggregate software distribution containing programs from several different sources. The license shall not require a royalty or other fee for such sale.
Rationale: By constraining the license to require free redistribution, we eliminate the temptation for licensors to throw away many long-term gains to make short-term gains. If we didn’t do this, there would be lots of pressure for cooperators to defect.
2. Source Code
The program must include source code, and must allow distribution in source code as well as compiled form. Where some form of a product is not distributed with source code, there must be a well-publicized means of obtaining the source code for no more than a reasonable reproduction cost, preferably downloading via the Internet without charge. The source code must be the preferred form in which a programmer would modify the program. Deliberately obfuscated source code is not allowed. Intermediate forms such as the output of a preprocessor or translator are not allowed.
Rationale: We require access to un-obfuscated source code because you can’t evolve programs without modifying them. Since our purpose is to make evolution easy, we require that modification be made easy.
3. Derived Works
The license must allow modifications and derived works, and must allow them to be distributed under the same terms as the license of the original software.
Rationale: The mere ability to read source isn’t enough to support independent peer review and rapid evolutionary selection. For rapid evolution to happen, people need to be able to experiment with and redistribute modifications.
4. Integrity of The Author’s Source Code
The license may restrict source-code from being distributed in modified form only if the license allows the distribution of “patch files” with the source code for the purpose of modifying the program at build time. The license must explicitly permit distribution of software built from modified source code. The license may require derived works to carry a different name or version number from the original software.
Rationale: Encouraging lots of improvement is a good thing, but users have a right to know who is responsible for the software they are using. Authors and maintainers have reciprocal right to know what they’re being asked to support and protect their reputations.
Accordingly, an open-source license must guarantee that source be readily available, but may require that it be distributed as pristine base sources plus patches. In this way, “unofficial” changes can be made available but readily distinguished from the base source.
5. No Discrimination Against Persons or Groups
The license must not discriminate against any person or group of persons.
Rationale: In order to get the maximum benefit from the process, the maximum diversity of persons and groups should be equally eligible to contribute to open sources. Therefore we forbid any open-source license from locking anybody out of the process.
Some countries, including the United States, have export restrictions for certain types of software. An OSD-conformant license may warn licensees of applicable restrictions and remind them that they are obliged to obey the law; however, it may not incorporate such restrictions itself.
6. No Discrimination Against Fields of Endeavor
The license must not restrict anyone from making use of the program in a specific field of endeavor. For example, it may not restrict the program from being used in a business, or from being used for genetic research.
Rationale: The major intention of this clause is to prohibit license traps that prevent open source from being used commercially. We want commercial users to join our community, not feel excluded from it.
7. Distribution of License
The rights attached to the program must apply to all to whom the program is redistributed without the need for execution of an additional license by those parties.
Rationale: This clause is intended to forbid closing up software by indirect means such as requiring a non-disclosure agreement.
8. License Must Not Be Specific to a Product
The rights attached to the program must not depend on the program’s being part of a particular software distribution. If the program is extracted from that distribution and used or distributed within the terms of the program’s license, all parties to whom the program is redistributed should have the same rights as those that are granted in conjunction with the original software distribution.
Rationale: This clause forecloses yet another class of license traps.
9. License Must Not Restrict Other Software
The license must not place restrictions on other software that is distributed along with the licensed software. For example, the license must not insist that all other programs distributed on the same medium must be open-source software.
Rationale: Distributors of open-source software have the right to make their own choices about their own software.
Yes, the GPL v2 and v3 are conformant with this requirement. Software linked with GPLed libraries only inherits the GPL if it forms a single work, not any software with which they are merely distributed.
10. License Must Be Technology-Neutral
No provision of the license may be predicated on any individual technology or style of interface.
Rationale: This provision is aimed specifically at licenses which require an explicit gesture of assent in order to establish a contract between licensor and licensee. Provisions mandating so-called “click-wrap” may conflict with important methods of software distribution such as FTP download, CD-ROM anthologies, and web mirroring; such provisions may also hinder code re-use. Conformant licenses must allow for the possibility that (a) redistribution of the software will take place over non-Web channels that do not support click-wrapping of the download, and that (b) the covered code (or re-used portions of covered code) may run in a non-GUI environment that cannot support popup dialogues.
The Open Source Definition was originally derived from the Debian Free Software Guidelines (DFSG).
