I came to be called so the script (in English the meaning of "a script, the script") referring to the simple language description method.
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Summary
I say the simple programming language whole to turn more than the meaning mentioned above, and to describe a relatively simple program. I do not add a model to a variable, and there is the definition to call a dynamic model charge account language a script language. But a close definition to the distinction do not exist. There are many things adopting an interpreter method, but the run-time use compiling is prosperous for a performance enhancement. On the other hand, it is a compiler method, but the languages that I can carry out by 1 command from a source code including the go run subcommand of the Go language increase, and, as for "this language, as for "this language, a compiler" and the one which I am particular about are nonsense an interpreter", but there is many I am particular about, turning probably because I am seen for the plain distinction.
Examples of the former (programming language to describe movement contents of the applications software like a script, and to control it) will include the JavaScript for the shell script for the shell of the UNIX, LISP for Emacs, the Web browser.
Examples of the latter (the programming language whole to relatively describe a simple program that turned, and was given meaning to) include perl and PHP. As for perl, a former meaning to describe the operation of the text processing tool was strong in the early days, but in late years [when?] Then it may be said that it developed as a programming language to build a dynamic website (bulletin boards) using CGI mainly at the point of the latter meaning.
In addition, I want to warn you although being very rare because I may call the programming language that I used to implement specific software with a script language. In this sense, one to call "a description language" is desirable. For example, it may be said that a description language of the UNIX is C language.
The following definition is possible, too. It is a language to use to enable it to add a certain function without building the whole a certain program again. For example, it is Emacs Lisp to have been prepared to add a new function to Emacs, and it is SSI and PHP that it was thought to add a function to an HTTP server. These work by an interpreter method in many cases, but there is the thing having mechanism to compile it like a case of Emacs, and to operate fast.
Because it was useful enough even the name called the script language arranged some basic functions sequentially, and to define the new function, I would be touched by the implication such as "a script description". However, I do not only describe movement easily. I possess the data structure description as the programming language, control structure description ability so that the movement that many script languages are complicated enough describes it.
History
The world's first interactive shell was developed for the remote control of the time sharing system in the 1960s. And the method that demand for scripting used the file which stored birth, a simple macrocommand and command line for to omit trouble to devote itself to many times was developed in a command line same an operator by the keyboard of the terminal. This finally led to the development of the shell script. In addition, a very basic implanted script function was developed to facilitate the operation of the batch mode which a human being did not exist among in development of the large, complicated application. In other words, I comprised a function to interpret the order line that a user wrote as some programs, and to carry out. The order line of this case was written by a very special language and virtually buried a program in a program.
As for the script which was low speed written as high-speed programming languages such as the C language in Bourne Shell and AWK, there was a difference in performance clearly historically. However, the performance difference shrank with a technological change, and JAVA and LISP, perl, an interpreter type language such as Python came to be used as a general programming language widely.
It is designed as a general-purpose script language and can speak the language such as Tcl and Lua in form to bury in application and can use it alone. The systems such as Visual Basic for Applications (VBA) are strongly tied to the automation system of the system becoming the base. It has a clear good point to bury a general-purpose script language without developing a new language every application. I omit trouble to develop the function that a developer interprets a language from the beginning and can omit trouble of the learning because the user can speak a known language.
Common Gateway Interface (CGI) makes it possible to control a Web server by a script language. A script language spoken for CGI use early includes perl, ASP, PHP.
Depending on software, I cope with plural different script languages. A recent Web browser includes the language that can expand browser oneself, and, as a standard implantation language for the browser control, there are ECMAScript (JavaScript) and CSS and HTML.
Kinds of the script language were produced by automation of the job control, and perform start and the control of the system program. It may be said that an ancestor of the shells includes Job Control Language (JCL, job control language) of IBM in this sense. Pro-handling of this kind of language (interpreter) most are called a command-line interpreter such as COMMAND.COM of shell and MS-DOS of the UNIX. There is other AppleScript to be able to write a script by a command such as English. In Mac OS X, I can build the whole application using Cocoa and AppleScript or a JavaScript [1].
GUI script
The special script languages for control of the computers were produced by an appearance of GUI. It is a language to exchange that the systems such as a window, a menu, the button were formed, and it simulates what a human hand performs. I automate that a user performs it, and these languages are standardized, and are called macrolanguages generally.
I can control any application to work on a GUI-based computer, but a macrolanguage theoretically exists in response to the specific application and operating system generally. However, there is the language to recognize a graphical object from the pixel placement on the screen among them, and to operate and is manipulability without, in that case, depending on the OS and application.
Language for exclusive use of the application
Most of large-scale application programs include an inherent script language, and a user of the application uses it as needed. Similarly, there is the script language that is inherent to most of TV game systems and is used for behavior of NPC and environmental programming. Such a language is designed only for one application. Outwardly there is the thing which is similar to a specific general-purpose language (with QuakeC, for example, similar to C language in Quake), but often has the special function that there is not for a general-purpose language. Emacs Lisp is a dialect of the LISP language fully equipped with a function, but possesses a lot of special functions that are convenient for the extension and modification of the function of Emacs. I can consider the script language for exclusive use of the application to be a language peculiar to domain specialized in specific application.
Web browser
A Web browser is application to display a web page. An exclusive language to control the operation has been developed. For example, there is XSLT to convert a JavaScript, VBScript (I work only in Internet Explorer) of Microsoft, XUL (I work only in Firefox) of the Mozilla project, XML contents into a new form, and to display it. Technique using XML and the combination of JavaScripts comes to be adopted widely to make the impression of the user better, and to draw a reaction and comes to be touched to the name called the Ajax.
Web server
On the server side in the HTTP link, even dynamic contents servers such as application server or CMS utilize various scripting technique. It is PHP, JSP, ASP that is used well in this domain, but, besides, Ruby on Rails gets popularity in a part.
Text processing language
The text processing is one of the uses of a certain script language for a long time. The script written for AWK, sed, the grep that were a tool of the UNIX has been used to automate the handling of about the configuration file and the log file text format. A regular expression is important in this field. By the script language for the text processing, I express structure for the processing using a regular expression formally.
Originally I was developed for the purpose of the thing more than the limits of the text processing tool, but perl grows up for a general-purpose language now.
The languages such as perl were born as a script language, but grew up for a programming language to be usable in a wider use. By a language similar to perl, I am interpreted during practice, and there is memory management capability and may be called "a script language" because the dynamic language resembles it mutually each. However, there is really the language that is often spoken in the description of the application body. Generally, the author of those languages does not call it "a script language" by oneself.
Expansion / implantation type language
The language to be able to bury in an application program as a substitute of the script language for exclusive use of the application has been designed how many until now. An application programmer elaborates "the hook" for the script language for a program (I use the C language mainly) to let you control the application. Such a language is used in a use same as an expansion language for exclusive use of the application, but there is an advantage to be able to share the skill about the script with different application. The JavaScript was born as a script language in the Web browser, and the use almost still spread out as a language for the general-purpose implantation because it was standardized as ECMAScript. SpiderMonkey which Mozilla in particular implemented is buried in some environment including Yahoo! Widget Engine. As other examples burying implementation (processing system) of ECMAScript, there are Adobe Flash (ActionScript) and Adobe Acrobat (for the scripting of the PDF file) which are a product of Adobe Systems.
Tcl was born as an expansion language, but is often used as a general-purpose language in the same way as Python, perl, Ruby.
It is complicated and, by the application that a use was limited to, comprises an implanted programming language separately from the function that I can offer in normal user interface and provides a further control in a user. For example, 3D authoring tool Maya incorporates a script language MEL. In addition, Blender adopts Python in the use.
A case to add a function to frequently when carry it out when try it in various ways, (e.g., a game engine) uses an implanted language, too. I show power, and prototyping under development can play with a function of the application even if I do not know the core part of the program. Lua and Python are famous, but, for the script language of this use, there are other AngelScript or Squirrel.
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Constitution of the OS of a monolithic kernel and the microkernel
Conception diagram of the microkernel
The microkernel (British: microkernel) is the name of the kernel part of design thought of the operating system and such OS. A way of thinking that I leave only a minimum in the kernel space among various functions that the OS takes and can simplify an overall design by moving the remainder to the user level, and, as a result, the performance can improve. Because the kernel body is limited to a small function, I am called "microkernel", but may not necessarily constitute the small OS.
With an appearance of the microkernel, I came to call the conventional OS "a monolithic kernel" (will called the kernel of the monolith).
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Characteristic
At first I limit a function offered in kernel space to virtualization, process control, interprocess communicationof the memory space and, in the pure microkernel, map the interrupts with respect for all communication. On top of that, I implement an associate kernel function such as file system and the device driver as those application and operate it in user space. A plural number operates those function sets by the unit called the server in some cases.
The merit of having such a form,
Improvement (I can perform Extensions, debugging easily) of the OS development efficiency
I can update the OS except the kernel without stopping the whole system
It becomes easy to build the OS specialized in application to provide only a necessary function
などである. In addition, it is advantageous to use of large-scale resources because generally the abstract degree of resources is high in the microkernel and can implement multiprocessor correspondence and communication of the network transmission naturally.
On the other hand, several-fold loss may appear from several percent when the overhead of function aspect each other is big and implements the function that is equal to a monolithic kernel to use interprocess communication at every place. (co-location) which I move a necessary function to the kernel space to avoid in particular the cost of the context switch and may operate like a monolithic kernel in an appearance.
History
The kernel of the early OS was relatively small partly because the memory capacity of the computer was small. As the ability of the computer grew up, the number of devices which a kernel must control increased. Still generally it was small even if, for example, the kernel of the original UNIX included device driver and file system. When address space spread to 32 bits from 16 bits, a kernel design ceased to be restricted by the hardware architecture, and the growth of the kernel began.
It is Berkeley Software Distribution to have become the beginning of the enlargement of the UNIX kernel (BSD). In addition to the role of the previous OS, I add plural file system by the BSD and include complete TCP/IP protocol stack, and various imagination devices which can work, and do an existing program on a network are added. I succeeded in a compact and high-performance OS design by the UNIX standardizing a resource in the concept called the file, and letting you joined a small process to treat a file together with a pipe and communicate mutually. However, with a change of the later use environment, resources not to be able to necessarily treat as a file increase. For example, the network communication is carried out in the concept called the socket, but the socket is not a file. As a result, it may be said that a situation that I am similar in a postscript, and the cord named the fault lets the OS enlarge occurred. Such a growth continued for years, and the source code of the kernel was enlarged in millions of lines. As a result, the possibility that a bug was underlying increased, and difficulty of the maintenance increased.
The microkernel begins in the point of view called such a "re-design of the UNIX". It was said that the microkernel design facilitated the management of the cord theoretically by cutting and bringing down the service group that was a part of the kernel between the user sky. In addition, it was thought that security and stability rose by reducing the quantity of the cord which worked by kernel mode. For example, it can continue functioning for the whole system because the microkernel is not affected even if network service crashes by buffer overrun.
The direct problems of the thing consisting of the cords that there are many OS's,
A memory area (footprint of the kernel space) that kernel in itself occupies grows big
It is disadvantageous to transplant characteristics and maintenance
といったものである. Furthermore, the implementation that I did not assume at the time of UNIX development such as multiprocessor and the virtual memory with the increase of calculator resources appeared, and it was thought that the refinement of the OS concept including them was necessary.
Therefore it is microkernel that I take "large-scale resources" and "high-speed communication" into consideration, and reached the development idea of the UNIX called "the cooperation movement by the process to communicate mutually". I was as a central concept with a file in the UNIX, but I put the principal objective into a process and communication in the microkernel, and every resource such as interrupt and I/O is abstracted thoroughly.
The microkernel developed in such a background in the 1980s was accompanied by some trials to let an existing built-in kernel fit a new system. With enormous work, careful cord management was required to develop device driver, a protocol stack, file system and other low-level systems included in a conventional kernel newly at a time. The service implemented as a program of the user space works like a normal user's program. Therefore not only handling of those services became easy, but also can optimize the left kernel part without minding a side effect. Furthermore, I could build the totally new OS on the common core region if I said and contributed to an OS study.
In addition, the reuse of the calculator resources which became old then was considered. In other words, it is a way of thinking that I connect it on the network even if it is an old system and can utilize as resources if transplant characteristics use the compact OS highly.
Early Local Area Network comes up in the 1980s, and the microkernel is very promising; was said technically. If it employs mechanism to scatter the functions of the kernel in the user space, this is because it can scatter systems on the network. The early microkernel such as Mach was proved to have a problem with performance, but considered that an advantage was bigger than it and played a key role of the OS study until the end of 1990s. In implemented Mach, I really succeeded in reduction of the quantity of original expected cord. An abstract degree is high, and the good microkernel with possibility is proper for a trend and is considered to be the thing which will be promising in the future at this time. However, the performance of the computer improved markedly in comparison with network performance in the meantime and was not able to ignore the issue of performance of the microkernel in consideration of an advantage of the ease of the development either. Various trials that performance improved an existing system were accomplished, but overheads always became the problem, and it was necessary to return the server which became the program of the user space to the kernel for the performance enhancement. It was not talked about the large-scale trial such as Mach by 2000, but the Mach kernel upgraded version called XNU which OPENSTEP adopted is adopted in Darwin and OS X [1]. As of 2012, Mach-based GNU Hurd functions, and Arch Linux and the test copy of Debian which adopted it are moving.
The large-scale study of the microkernel burnt down, but was able to continue researching and developing it. Most of issue of performance in the early microkernel design came to be considered to have been caused by the desire of the designer to want to implement services as many as possible by the system of the single use not the thing by the basic requirements of the concept. I used the assembly code and I depended on the architecture of the processor and usually did that I supported it by software and adopted a more practical approach to a problem, and the microkernel that performance was improved dramatically came to appear. The name called nanokernel (nanokernel) was used to distinguish such a new generation microkernel from the implementation including conventional many system services. However, I am not called the nanokernel when the shifts from conventional microkernel to a nanokernel are almost completed.
As a method in conjunction with microkernel and the closeness with エクソカーネル (English version) [2]. エクソカーネル has many a hyper visor and common points [3], but I do not insist on the very small nature and am specialized in virtual machine support. Actually, the L4 microkernel is used for the implementation of the hyper visor well.
Interprocess communication
Interprocess communication (IPC) is some kind of mechanism to enable the communication between processes, and the message transmission is used well. The shared memory is a kind of the interprocess communication mechanism closely, too, but, speaking of IPC, points to the message in microkernel generally. By IPC, I can build the OS by some small programs called the server and can call a server from others using IPC. I can implement the support of neighboring hardware like that, too, and there are device driver, a protocol stack, the file system of the network, various things including the graphics to the server.
There are an expression and the ceremony of async in IPC in the same period. Async IPC is similar to network communication. The transmission side publishes a message and continues processing. It is notified of whether the reception side checks the arrival of the message regularly by some kind of detection mechanism. A kernel manages a buffer and the cue for the message in async IPC, and a kernel handles the buffer overflow. In addition, two times of messages are copied (from the transmission side from a kernel and a kernel the reception side). In synchronization IPC, the transmission side or the reception side is blocked until another becomes the IPC possibility. The buffering is unnecessary for the multiple copy, too, but needs adroitness for programming because it is necessary for both to meet explicitly. Many programmers like the reception in the async transmission and the same period.
The first generation microkernel supported both synchronization IPC and async IPC generally, but the performance was bad. Jochen Liedtke showed that there was the cause for design and implementation of the IPC mechanism. He made IPC cost a one-tenth or less in L4 microkernel [4]. In IPC, both the transmission and the reception are supported in system call and it is only a synchronization type and hands data as many as possible in registers. Furthermore, Liedtke introduced a concept called direct process switch and, in the case of IPC, performed a direct (incomplete) context switch from the transmission side to the reception side. Therefore, in L4, I can transfer the message in the register when I hand some or all of the message in register group without copying it really. Furthermore, I remove an overhead calling a scheduler. This is suitable for IPC when I call a server for RPC in particular. Another optimization includes a thing called lazy scheduling, and do not scan a scheduling cue in IPC; keep on having blocked a thread by a lady cue during IPC to need it. When a scheduler is called, I put such a thread into a suitable waiting queue.
Even if much communication is the ceremony of synchronization by the client server type system basically and used the primitive which is async, clients usually call servers and will wait for a reply. Because the implementation became effective, the one came to provide only synchronization IPC primitive in the microkernel after L4. Synchronization can implement async IPC on IPC primitive using a supporting thread. However, it becomes clear for asynchronous communication support with the commercial product which adopted L4 that notice of async mechanism is necessary and adds it. A system such as this signal is not a thing transferring data, and the buffering by the kernel is unnecessary.
Another is blocked until one side of the communication becomes able to reply in synchronization IPC. Therefore, a deadlock state occurs easily when I use IPC without any restriction. In addition, when prevent a client sending a demand, and a reply from meeting; easily such as the denial-of-service attack is in a condition. Therefore, you must provide means to prevent a block to cross for a long term in synchronization IPC. Much microkernel provides time-out for IPC summons and limit flying hours. The setting of the time-out time is difficult, and, as a result, the time-out of the client is unlimited and really often does the time-out of the server with zero. As a result, it did not allow you to set time-out time optionally, and it was in a tendency to prepare only for a flag to show whether you let you fail in IPC immediately when a partner could not reply. I will thereby select whether it is zero as time-out time, or it is unlimited. The recent version of L4 and Minix comes to look like it, too (I can set time-out time optionally in QNX and former L4).
Server
A server in the microkernel is something like daemon, but some servers are given the special privilege which can access a part of the physical memory space. A server of the device driver becomes able to thereby communicate with hardware directly.
A basic server in the general-purpose microkernel includes a file system server, a device driver server, a network server, a display server, the server of the user interface device. I almost cover the service that the monolithic kernel of the Unix system provides in these servers group. The required server starts at the time of a setup and starts service. The server works in environment like the user application, and the development is similar to application, too. The frequent build and reboot becoming necessary for kernel development are unnecessary.
Furthermore, even if a disorder occurs with a server, the whole system does not crash and should merely reboot the server. However, because a part of the system state may be lost because a disorder occurs with a server; as for the application side corresponding to the server obstacle it is necessary. 例えば、TCP/IP接続を担うサーバがあるとする。 このサーバを再起動すると、アプリケーションから見てコネクションが失われることになるが、これは通常のネットワークでも起き得る障害である。 しかしアプリケーションが障害発生を予期していないサービスの場合、アプリケーションのコードを修正する必要がある。 QNXではサーバの再起動への対応として QNX High Availability Toolkit が提供されている[5]。
Direct Memory Access (DMA) を頻繁に行うデバイスドライバは、カーネルのデータ構造を含めた物理メモリの任意の位置に書き込める必要がある。そのようなドライバは信頼されていなければならないが、必ずしもカーネル内に含まれている必要はない。実際、カーネルの一部だからといってデバイスドライバがより信頼できるというわけではない。
ユーザーモードのドライバは実際にはマイクロカーネルより古くから存在する。1967年の Michigan Terminal System (MTS) で初めて（ファイルシステムも含めた）ユーザー空間のドライバがサポートされた[7]。歴史的には、ドライバをカーネルに含めることはあまり問題とされなかった。周辺デバイスの数は少なく、特権が必須だったためであり、カーネルに含めることで性能問題を防いでいた。Unixもそのスタイルを踏襲し[8]、Linuxや Windows XP 以前のWindowsも同様だった。デバイスの種類が豊富になってくると、ドライバのコード量も増大するようになり、カーネル全体に占める割合も増えていった。
複数サーバの商用システムはいくつか存在しており、例えばリアルタイムオペレーティングシステムのQNXやIntegrity（英語版）がある。そういったシステムとモノリシックなシステムとの包括的性能比較は公表されたことがない。さらに言えばそれら商用システムでは性能が最重要課題ではないようで、割り込み応答時間の保証や頑健性のための単純さが強調されている。複数サーバの高性能OSを構築する試みとしてIBMの Sawmill Linux というプロジェクトがあった[15]。しかし、このプロジェクトは完了することなく中止された。
近年のマイクロカーネル研究開発は、カーネルAPIの形式仕様とそのAPIのセキュリティ属性の形式的証明に集中している。第一の例として、EROSでの隔離機構の数学的証明があり、EROS API を単純化したモデルに基づいている[19]。より最近の例として、L4のバージョンの一種である seL4 のプロテクションモデルについて自動検証された包括的な証明がなされている[20]。
カーネルコードの量、すなわちハードウェアの特権モードで実行されるコードの量が極めて小さいカーネル。カーネルが極めて小さいことを強調する際に「ピコカーネル」という呼称も使われた。「ナノカーネル」という用語を生み出したのは Jonathan S. Shapiro で、The KeyKOS NanoKernel Architecture (1992) という論文で初めて使っている。それはMachへの冷笑的反応であった。彼はMachについて、本質的に非構造的であり、モノリシックであるのにマイクロカーネルと主張しているだけで、置き換えようとしているものより性能が悪いと評した。その用語が他でも使われ、さらにピコカーネルという呼称が生まれた背景には、従来のマイクロカーネルが「カーネルが小さい」という点から大きく外れていったことを示唆している。その後、ナノカーネルとピコカーネルはマイクロカーネルと同じ意味で使われるようになった。
^Alexander, Michael T. (1971). "Organization and Features of the Michigan Terminal System". Proceedings of the November 16–18, 1971, fall joint computer conference40: 589–591. doi:10.1145/1478873.1478951.
^Lions, John (1977-08-01). Lions' Commentary on UNIX 6th Edition, with Source Code. Peer-To-Peer Communications. ISBN978-1-57398-013-5.
^ abLiedtke, Jochen (December 1995). "On µ-Kernel Construction". 15th ACM symposium on Operating Systems Principles. pp. 237–250. doi:10.1145/224056.224075
^Chen, Bradley; Bershad, Brian (December 1993). "The Impact of Operating System Structure on Memory System Performance". 14th ACM Symposium on Operating System Principles. Asheville, NC, USA. pp. 120–33. doi:10.1145/168619.168629
Dan Hildebrand (1992). "An Architectural Overview of QNX". Proceedings of the Workshop on Micro-kernels and Other Kernel Architectures: 113–126. ISBN1-880446-42-1. - the basic QNX reference.
Black, D.L., Golub, D.B., Julin, D.P., Rashid, R.F., Draves, R.P., Dean, R.W., Forin, A., Barrera, J., Tokuda, H., Malan, G., and Bohman, D. (March 1992). "Microkernel Operating System Architecture and Mach". J. of Information Processing14 (4). - the basic Mach reference.
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