"Hello, World!" program
A "Hello, World!" program is a computer program that outputs or displays the message "Hello, World!". Because it is simple in most programming languages, it is used to illustrate the basic syntax of a programming language and is the first program that those learning to code write. A "Hello, World!" program is traditionally used to introduce novice programmers to a programming language. "Hello, world!" is traditionally used in a sanity test to make sure that a computer language is installed, that the operator understands how to use it. While small test programs have existed since the development of programmable computers, the tradition of using the phrase "Hello, world!" as a test message was influenced by an example program in the seminal book The C Programming Language. The example program from that book prints "hello, world", was inherited from a 1974 Bell Laboratories internal memorandum by Brian Kernighan, Programming in C: A Tutorial: The C version was preceded by Kernighan's own 1972 A Tutorial Introduction to the Language B, where the first known version of the program is found in an example used to illustrate external variables: main a'hell'.
The phrase is divided into multiple variables because in B, a character constant is limited to four ASCII characters. The previous example in the tutorial printed hi! on the terminal, the phrase hello, world! was introduced as a longer greeting that required several character constants for its expression. The Jargon File claims that hello, world originated instead with BCPL; this claim is supported by the archived notes of the inventors of BCPL, Prof. Brian Kernighan at Princeton and Martin Richards at Cambridge. For modern languages, world programs vary in sophistication. For example, the Go programming language introduced a multilingual program, Sun demonstrated a Java hello, world based on scalable vector graphics, the XL programming language features a spinning Earth hello, world using 3D graphics. While some languages such as Perl, Python or Ruby may need only a single statement to print "hello, world", a low-level assembly language may require dozens of commands. Mark Guzdial and Elliot Soloway have suggested that the "hello, world" test message may be outdated now that graphics and sound can be manipulated as as text.
There are many variations on the punctuation and casing of the phrase. Variations include the presence or absence of the comma and exclamation mark, the capitalization of the'H', both the'H' and the'W', or neither; some languages are forced to implement different forms, such as "HELLO WORLD", on systems that support only capital letters, while many "hello, world" programs in esoteric languages print out a modified string. For example, the first non-trivial Malbolge program printed "HEllO WORld", this having been determined to be good enough. There are variations in spirit, as well. Functional programming languages, like Lisp, ML and Haskell, tend to substitute a factorial program for Hello, World, as functional programming emphasizes recursive techniques, whereas the original examples emphasize I/O, which violates the spirit of pure functional programming by producing side effects. Languages otherwise capable of Hello, World may be used in embedded systems, where text output is either difficult or nonexistent.
For devices such as microcontrollers, field-programmable gate arrays, CPLD's, "Hello, World" may thus be substituted with a blinking LED, which demonstrates timing and interaction between components. The Debian and Ubuntu Linux distributions provide the "hello, world" program through the apt packaging system. While of itself useless, it serves as a sanity check and a simple example to newcomers of how to install a package, it is more useful for developers, however, as it provides an example of how to create a.deb package, either traditionally or using debhelper, the version of hello used, GNU Hello, serves as an example of how to write a GNU program. Time to "Hello World" is a metric for how long it takes to get a "Hello World" program running from scratch in a given programming language. "99 Bottles of Beer" as used in computer science Foobar Java Pet Store Just another Perl hacker List of basic computer science topics Trabb Pardo-Knuth algorithm List of hello world programs at Wikibooks Rösler, Wolfram.
"Hello World Collection". Helloworldcollection.de. "Hello world/Text". Rosetta Code. "Unsung Heroes of IT / Part One: Brian Kernighan". TheUnsungHeroesOfIT.com. Archived from the original on 2016-03-26. Retrieved 2014-08-23
Oracle Corporation is an American multinational computer technology corporation headquartered in Redwood Shores, California. The company specializes in developing and marketing database software and technology, cloud engineered systems, enterprise software products — its own brands of database management systems. In 2018, Oracle was the third-largest software maker by revenue, after Alphabet; the company develops and builds tools for database development and systems of middle-tier software, enterprise resource planning software, customer relationship management software, supply chain management software. Larry Ellison co-founded Oracle Corporation in 1977 with Bob Miner and Ed Oates under the name Software Development Laboratories. Ellison took inspiration from the 1970 paper written by Edgar F. Codd on relational database management systems named "A Relational Model of Data for Large Shared Data Banks." He heard about the IBM System R database from an article in the IBM Research Journal provided by Oates.
Ellison wanted to make Oracle's product compatible with System R, but failed to do so as IBM kept the error codes for their DBMS a secret. SDL changed its name to Relational Software, Inc in 1979 again to Oracle Systems Corporation in 1982, to align itself more with its flagship product Oracle Database. At this stage Bob Miner served as the company's senior programmer. On March 12, 1986, the company had its initial public offering. In 1995, Oracle Systems Corporation changed its name to Oracle Corporation named Oracle, but sometimes referred to as Oracle Corporation, the name of the holding company. Part of Oracle Corporation's early success arose from using the C programming language to implement its products; this eased porting to different operating systems. 1979: offers the first commercial SQL RDBMS 1983: offers a VAX-mode database 1984: offers the first database with read-consistency 1986: offers a client-server DBMS 1987: introduces UNIX-based Oracle applications 1988: introduces PL/SQL.
1992: offers full applications implementation methodology 1995: offers the first 64-bit RDBMS 1996: moves towards an open standards-based, web-enabled architecture 1999: offers its first DBMS with XML support 2001: becomes the first to complete 3 terabyte TPC-H world record 2002: offers the first database to pass 15 industry standard security evaluations 2003: introduces what it calls "Enterprise Grid Computing" with Oracle10g 2005: releases its first free database, Oracle Database 10g Express Edition 2006: acquires Siebel Systems 2007: acquires Hyperion Solutions 2008: Smart scans in software improve query-response in HP Oracle Database Machine / Exadata storage 2010: acquires Sun Microsystems 2013: begins use of Oracle 12c, capable of providing cloud services with Oracle Database 2014: acquires Micros Systems 2016: acquires NetSuite Inc. Oracle ranked No. 82 in the 2018 Fortune 500 list of the largest United States corporations by total revenue. According to Bloomberg, Oracle's CEO-to-employee pay ratio is 1,205:1.
The CEO's compensation in 2017 was $108,295,023. Meanwhile, the median employee compensation rate was $89,887. Oracle designs and sells both software and hardware products, as well as offering services that complement them. Many of the products have been added to Oracle's portfolio through acquisitions. Oracle's E-delivery service provides documentation. Oracle Database Release 10: In 2004, Oracle Corporation shipped release 10g as the latest version of Oracle Database. Release 11: Release 11g became the current Oracle Database version in 2007. Oracle Corporation released Oracle Database 11g Release 2 in September 2009; this version was available in four commercial editions—Enterprise Edition, Standard Edition, Standard Edition One, Personal Edition—and in one free edition—the Express Edition. The licensing of these editions shows various restrictions and obligations that were called complex by licensing expert Freirich Florea; the Enterprise Edition, the most expensive of the Database Editions, has the fewest restrictions — but has complex licensing.
Oracle Corporation constrains the Standard Edition and Standard Edition One with more licensing restrictions, in accordance with their lower price. Release 12: Release 12c became available on July 1, 2013. Oracle Corporation has acquired and developed the following additional database technologies: Berkeley DB, which offers embedded database processing Oracle Rdb, a relational database system running on OpenVMS platforms. Oracle acquired Rdb in 1994 from Digital Equipment Corporation. Oracle has since made many enhancements to this product and development continues as of 2008. TimesTen, which features in-memory database operations Oracle Essbase, which continues the Hyperion Essbase tradition of multi-dimensional database management MySQL, a relational database management system licensed under the GNU General Public License developed by MySQL AB Oracle NoSQL Database, a scalable, distributed key-value NoSQL database Oracle Fusion Middleware is a family of middleware
Unix is a family of multitasking, multiuser computer operating systems that derive from the original AT&T Unix, development starting in the 1970s at the Bell Labs research center by Ken Thompson, Dennis Ritchie, others. Intended for use inside the Bell System, AT&T licensed Unix to outside parties in the late 1970s, leading to a variety of both academic and commercial Unix variants from vendors including University of California, Microsoft, IBM, Sun Microsystems. In the early 1990s, AT&T sold its rights in Unix to Novell, which sold its Unix business to the Santa Cruz Operation in 1995; the UNIX trademark passed to The Open Group, a neutral industry consortium, which allows the use of the mark for certified operating systems that comply with the Single UNIX Specification. As of 2014, the Unix version with the largest installed base is Apple's macOS. Unix systems are characterized by a modular design, sometimes called the "Unix philosophy"; this concept entails that the operating system provides a set of simple tools that each performs a limited, well-defined function, with a unified filesystem as the main means of communication, a shell scripting and command language to combine the tools to perform complex workflows.
Unix distinguishes itself from its predecessors as the first portable operating system: the entire operating system is written in the C programming language, thus allowing Unix to reach numerous platforms. Unix was meant to be a convenient platform for programmers developing software to be run on it and on other systems, rather than for non-programmers; the system grew larger as the operating system started spreading in academic circles, as users added their own tools to the system and shared them with colleagues. At first, Unix was not designed to be multi-tasking. Unix gained portability, multi-tasking and multi-user capabilities in a time-sharing configuration. Unix systems are characterized by various concepts: the use of plain text for storing data; these concepts are collectively known as the "Unix philosophy". Brian Kernighan and Rob Pike summarize this in The Unix Programming Environment as "the idea that the power of a system comes more from the relationships among programs than from the programs themselves".
In an era when a standard computer consisted of a hard disk for storage and a data terminal for input and output, the Unix file model worked quite well, as I/O was linear. In the 1980s, non-blocking I/O and the set of inter-process communication mechanisms were augmented with Unix domain sockets, shared memory, message queues, semaphores, network sockets were added to support communication with other hosts; as graphical user interfaces developed, the file model proved inadequate to the task of handling asynchronous events such as those generated by a mouse. By the early 1980s, users began seeing Unix as a potential universal operating system, suitable for computers of all sizes; the Unix environment and the client–server program model were essential elements in the development of the Internet and the reshaping of computing as centered in networks rather than in individual computers. Both Unix and the C programming language were developed by AT&T and distributed to government and academic institutions, which led to both being ported to a wider variety of machine families than any other operating system.
Under Unix, the operating system consists of many libraries and utilities along with the master control program, the kernel. The kernel provides services to start and stop programs, handles the file system and other common "low-level" tasks that most programs share, schedules access to avoid conflicts when programs try to access the same resource or device simultaneously. To mediate such access, the kernel has special rights, reflected in the division between user space and kernel space - although in microkernel implementations, like MINIX or Redox, functions such as network protocols may run in user space; the origins of Unix date back to the mid-1960s when the Massachusetts Institute of Technology, Bell Labs, General Electric were developing Multics, a time-sharing operating system for the GE-645 mainframe computer. Multics featured several innovations, but presented severe problems. Frustrated by the size and complexity of Multics, but not by its goals, individual researchers at Bell Labs started withdrawing from the project.
The last to leave were Ken Thompson, Dennis Ritchie, Douglas McIlroy, Joe Ossanna, who decided to reimplement their experiences in a new project of smaller scale. This new operating system was without organizational backing, without a name; the new operating system was a single-tasking system. In 1970, the group coined the name Unics for Uniplexed Information and Computing Service, as a pun on Multics, which stood for Multiplexed Information and Computer Services. Brian Kernighan takes credit for the idea, but adds that "no one can remember" the origin of the final spelling Unix. Dennis Ritchie, Doug McIlroy, Peter G. Neumann credit Kernighan; the operating system was written in assembly language, but in 1973, Version 4 Unix was rewritten in C. Version 4 Unix, still had many PDP-11 dependent codes, is not suitable for porting; the first port to other platform was made five years f
Java virtual machine
A Java virtual machine is a virtual machine that enables a computer to run Java programs as well as programs written in other languages that are compiled to Java bytecode. The JVM is detailed by a specification that formally describes what is required of a JVM implementation. Having a specification ensures interoperability of Java programs across different implementations so that program authors using the Java Development Kit need not worry about idiosyncrasies of the underlying hardware platform; the JVM reference implementation is developed by the OpenJDK project as open source code and includes a JIT compiler called HotSpot. The commercially supported Java releases available from Oracle Corporation are based on the OpenJDK runtime. Eclipse OpenJ9 is another open source JVM for OpenJDK; the Java virtual machine is an abstract computer defined by a specification. The garbage-collection algorithm used and any internal optimization of the Java virtual machine instructions are not specified; the main reason for this omission is to not unnecessarily constrain implementers.
Any Java application can be run only inside some concrete implementation of the abstract specification of the Java virtual machine. Starting with Java Platform, Standard Edition 5.0, changes to the JVM specification have been developed under the Java Community Process as JSR 924. As of 2006, changes to specification to support changes proposed to the class file format are being done as a maintenance release of JSR 924; the specification for the JVM was published as the blue book, The preface states: We intend that this specification should sufficiently document the Java Virtual Machine to make possible compatible clean-room implementations. Oracle provides tests that verify the proper operation of implementations of the Java Virtual Machine. One of Oracle's JVMs is named the other, inherited from BEA Systems is JRockit. Clean-room Java implementations include Kaffe, IBM J9 and Skelmir's CEE-J. Oracle owns the Java trademark and may allow its use to certify implementation suites as compatible with Oracle's specification.
One of the organizational units of JVM byte code is a class. A class loader implementation must be able to recognize and load anything that conforms to the Java class file format. Any implementation is free to recognize other binary forms besides class files, but it must recognize class files; the class loader performs three basic activities in this strict order: Loading: finds and imports the binary data for a type Linking: performs verification and resolution Verification: ensures the correctness of the imported type Preparation: allocates memory for class variables and initializing the memory to default values Resolution: transforms symbolic references from the type into direct references. Initialization: invokes Java code that initializes class variables to their proper starting values. In general, there are two types of class loader: bootstrap class loader and user defined class loader; every Java virtual machine implementation must have a bootstrap class loader, capable of loading trusted classes.
The Java virtual machine specification doesn't specify. The JVM operates on primitive references; the JVM is fundamentally a 32-bit machine. Long and double types, which are 64-bits, are supported natively, but consume two units of storage in a frame's local variables or operand stack, since each unit is 32 bits. Boolean, byte and char types are all sign-extended and operated on as 32-bit integers, the same as int types; the smaller types only have a few type-specific instructions for loading and type conversion. Boolean is operated on with 0 representing false and 1 representing true; the JVM has a garbage-collected heap for storing arrays. Code and other class data are stored in the "method area"; the method area is logically part of the heap, but implementations may treat the method area separately from the heap, for example might not garbage collect it. Each JVM thread has its own call stack, which stores frames. A new frame is created each time a method is called, the frame is destroyed when that method exits.
Each frame provides an "operand stack" and an array of "local variables". The operand stack is used for operands to computations and for receiving the return value of a called method, while local variables serve the same purpose as registers and are used to pass method arguments. Thus, the JVM is both a register machine; the JVM has instructions for the following groups of tasks: The aim is binary compatibility. Each particular host operating system needs its own implementation of the runtime; these JVMs interpret the bytecode semantically the same way, but the actual implementation may be different. More complex than just emulating bytecode is compatibly and efficiently im
Microsoft Windows is a group of several graphical operating system families, all of which are developed and sold by Microsoft. Each family caters to a certain sector of the computing industry. Active Windows families include Windows Embedded. Defunct Windows families include Windows Mobile and Windows Phone. Microsoft introduced an operating environment named Windows on November 20, 1985, as a graphical operating system shell for MS-DOS in response to the growing interest in graphical user interfaces. Microsoft Windows came to dominate the world's personal computer market with over 90% market share, overtaking Mac OS, introduced in 1984. Apple came to see Windows as an unfair encroachment on their innovation in GUI development as implemented on products such as the Lisa and Macintosh. On PCs, Windows is still the most popular operating system. However, in 2014, Microsoft admitted losing the majority of the overall operating system market to Android, because of the massive growth in sales of Android smartphones.
In 2014, the number of Windows devices sold was less than 25 %. This comparison however may not be relevant, as the two operating systems traditionally target different platforms. Still, numbers for server use of Windows show one third market share, similar to that for end user use; as of October 2018, the most recent version of Windows for PCs, tablets and embedded devices is Windows 10. The most recent versions for server computers is Windows Server 2019. A specialized version of Windows runs on the Xbox One video game console. Microsoft, the developer of Windows, has registered several trademarks, each of which denote a family of Windows operating systems that target a specific sector of the computing industry; as of 2014, the following Windows families are being developed: Windows NT: Started as a family of operating systems with Windows NT 3.1, an operating system for server computers and workstations. It now consists of three operating system subfamilies that are released at the same time and share the same kernel: Windows: The operating system for mainstream personal computers and smartphones.
The latest version is Windows 10. The main competitor of this family is macOS by Apple for personal computers and Android for mobile devices. Windows Server: The operating system for server computers; the latest version is Windows Server 2019. Unlike its client sibling, it has adopted a strong naming scheme; the main competitor of this family is Linux. Windows PE: A lightweight version of its Windows sibling, meant to operate as a live operating system, used for installing Windows on bare-metal computers, recovery or troubleshooting purposes; the latest version is Windows PE 10. Windows IoT: Initially, Microsoft developed Windows CE as a general-purpose operating system for every device, too resource-limited to be called a full-fledged computer. However, Windows CE was renamed Windows Embedded Compact and was folded under Windows Compact trademark which consists of Windows Embedded Industry, Windows Embedded Professional, Windows Embedded Standard, Windows Embedded Handheld and Windows Embedded Automotive.
The following Windows families are no longer being developed: Windows 9x: An operating system that targeted consumers market. Discontinued because of suboptimal performance. Microsoft now caters to the consumer market with Windows NT. Windows Mobile: The predecessor to Windows Phone, it was a mobile phone operating system; the first version was called Pocket PC 2000. The last version is Windows Mobile 6.5. Windows Phone: An operating system sold only to manufacturers of smartphones; the first version was Windows Phone 7, followed by Windows Phone 8, the last version Windows Phone 8.1. It was succeeded by Windows 10 Mobile; the term Windows collectively describes any or all of several generations of Microsoft operating system products. These products are categorized as follows: The history of Windows dates back to 1981, when Microsoft started work on a program called "Interface Manager", it was announced in November 1983 under the name "Windows", but Windows 1.0 was not released until November 1985.
Windows 1.0 was to achieved little popularity. Windows 1.0 is not a complete operating system. The shell of Windows 1.0 is a program known as the MS-DOS Executive. Components included Calculator, Cardfile, Clipboard viewer, Control Panel, Paint, Reversi and Write. Windows 1.0 does not allow overlapping windows. Instead all windows are tiled. Only modal dialog boxes may appear over other windows. Microsoft sold as included Windows Development libraries with the C development environment, which included numerous windows samples. Windows 2.0 was released in December 1987, was more popular than its predecessor. It features several improvements to the user memory management. Windows 2.03 changed the OS from tiled windows to overlapping windows. The result of this change led to Apple Computer filing a suit against Microsoft alleging infringement on Apple's copyrights. Windows 2.0
Linux is a family of free and open-source software operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991 by Linus Torvalds. Linux is packaged in a Linux distribution. Distributions include the Linux kernel and supporting system software and libraries, many of which are provided by the GNU Project. Many Linux distributions use the word "Linux" in their name, but the Free Software Foundation uses the name GNU/Linux to emphasize the importance of GNU software, causing some controversy. Popular Linux distributions include Debian and Ubuntu. Commercial distributions include SUSE Linux Enterprise Server. Desktop Linux distributions include a windowing system such as X11 or Wayland, a desktop environment such as GNOME or KDE Plasma. Distributions intended for servers may omit graphics altogether, include a solution stack such as LAMP; because Linux is redistributable, anyone may create a distribution for any purpose. Linux was developed for personal computers based on the Intel x86 architecture, but has since been ported to more platforms than any other operating system.
Linux is the leading operating system on servers and other big iron systems such as mainframe computers, the only OS used on TOP500 supercomputers. It is used by around 2.3 percent of desktop computers. The Chromebook, which runs the Linux kernel-based Chrome OS, dominates the US K–12 education market and represents nearly 20 percent of sub-$300 notebook sales in the US. Linux runs on embedded systems, i.e. devices whose operating system is built into the firmware and is tailored to the system. This includes routers, automation controls, digital video recorders, video game consoles, smartwatches. Many smartphones and tablet computers run other Linux derivatives; because of the dominance of Android on smartphones, Linux has the largest installed base of all general-purpose operating systems. Linux is one of the most prominent examples of open-source software collaboration; the source code may be used and distributed—commercially or non-commercially—by anyone under the terms of its respective licenses, such as the GNU General Public License.
The Unix operating system was conceived and implemented in 1969, at AT&T's Bell Laboratories in the United States by Ken Thompson, Dennis Ritchie, Douglas McIlroy, Joe Ossanna. First released in 1971, Unix was written in assembly language, as was common practice at the time. In a key pioneering approach in 1973, it was rewritten in the C programming language by Dennis Ritchie; the availability of a high-level language implementation of Unix made its porting to different computer platforms easier. Due to an earlier antitrust case forbidding it from entering the computer business, AT&T was required to license the operating system's source code to anyone who asked; as a result, Unix grew and became adopted by academic institutions and businesses. In 1984, AT&T divested itself of Bell Labs; the GNU Project, started in 1983 by Richard Stallman, had the goal of creating a "complete Unix-compatible software system" composed of free software. Work began in 1984. In 1985, Stallman started the Free Software Foundation and wrote the GNU General Public License in 1989.
By the early 1990s, many of the programs required in an operating system were completed, although low-level elements such as device drivers and the kernel, called GNU/Hurd, were stalled and incomplete. Linus Torvalds has stated that if the GNU kernel had been available at the time, he would not have decided to write his own. Although not released until 1992, due to legal complications, development of 386BSD, from which NetBSD, OpenBSD and FreeBSD descended, predated that of Linux. Torvalds has stated that if 386BSD had been available at the time, he would not have created Linux. MINIX was created by Andrew S. Tanenbaum, a computer science professor, released in 1987 as a minimal Unix-like operating system targeted at students and others who wanted to learn the operating system principles. Although the complete source code of MINIX was available, the licensing terms prevented it from being free software until the licensing changed in April 2000. In 1991, while attending the University of Helsinki, Torvalds became curious about operating systems.
Frustrated by the licensing of MINIX, which at the time limited it to educational use only, he began to work on his own operating system kernel, which became the Linux kernel. Torvalds began the development of the Linux kernel on MINIX and applications written for MINIX were used on Linux. Linux matured and further Linux kernel development took place on Linux systems. GNU applications replaced all MINIX components, because it was advantageous to use the available code from the GNU Project with the fledgling operating system. Torvalds initiated a switch from his original license, which prohibited commercial redistribution, to the GNU GPL. Developers worked to integrate GNU components with the Linux kernel, making a functional and free operating system. Linus Torvalds had wanted to call his invention "Freax", a portmant