In geology, any igneous rock dominated by the silicates pyroxene, amphibole, olivine, and mica. These minerals are high in magnesium and ferrous iron, and their presence gives mafic rock its characteristic dark colour. It is usually contrasted with felsic rock. Common mafic rocks include basalt and gabbro.
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Steelmaking method in which pure oxygen is blown through a long, movable lance into a bath of molten blast-furnace iron and scrap, in a steel furnace with a refractory lining called a converter. The oxygen initiates a series of heat-releasing reactions, including the oxidation of such impurities as silicon, carbon, phosphorus, and manganese; carbon dioxide is released, and the oxidation products of the other impurities form molten slag that floats on the molten steel. The advantages of using pure oxygen instead of air in refining iron into steel were recognized as early as the 1850s (see Bessemer process), but the process could not be commercialized until the late 1940s, when cheap, high-purity oxygen became available. Within 40 years it had replaced the open-hearth process and was producing more than half of all steel worldwide. Commercial advantages include high production rates, less labour, and steel with a low nitrogen content.
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Modification of the Bessemer process for converting pig iron into steel. The original Bessemer converter was not effective in removing the phosphorus from iron made from the high-phosphorus ores common in Britain and Europe. The invention of the basic process in England by Sidney G. Thomas (1850–1885) and Percy Gilchrist overcame this problem; the Thomas-Gilchrist converter was lined with a basic material such as burned limestone rather than an acid siliceous material. The introduction of the basic Bessemer process in 1879 made it possible for the first time for such high-phosphorus ore to be used for making steel.
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In computer programming, BASIC (an acronym for Beginner's All-purpose Symbolic Instruction Code) is a family of high-level programming languages. The original BASIC was designed in 1964 by John George Kemeny and Thomas Eugene Kurtz at Dartmouth in New Hampshire, USA to provide computer access to non-science students (at the time, nearly all use of computers required writing custom software, which was something only scientists and mathematicians tended to be able to do). The language and its variants became widespread on microcomputers in the late 1970s and home computers in the 1980s. BASIC remains popular to this day in a handful of highly modified dialects and new languages based on BASIC such as Microsoft Visual Basic.
Programming languages in the batch programming era tended to be designed, like the machines on which they ran, for specific purposes (such as scientific formula calculations or business data processing or eventually for text editing). Since even the newer, less expensive machines were still major investments, there was a strong tendency to consider efficiency to be the most important feature of a language. In general, these specialized languages were difficult to use and had widely disparate syntax.
As prices decreased, the possibility of sharing computer access began to move from research labs to commercial use. Newer computer systems supported time-sharing, a system which allows multiple users or processes to use the CPU and memory. In such a system the operating system alternates between running processes, giving each one running time on the CPU before switching to another. The machines had become fast enough that most users could feel they had the machine all to themselves. In theory, timesharing reduced the cost of computing tremendously, as a single machine could be shared among (up to) hundreds of users.
The eight design principles of BASIC were:
The language was based partly on the FORTRAN II and partly on the ALGOL 60, with additions to make it suitable for timesharing. (The features of other time-sharing systems such as JOSS and CORC, and to a lesser extent LISP, were also considered.) It had been preceded by other teaching-language experiments at Dartmouth such as the DARSIMCO (1956) and DOPE (1962 implementations of SAP and DART (1963) which was a simplified FORTRAN II). Initially, BASIC concentrated on supporting straightforward mathematical work, with matrix arithmetic support from its initial implementation as a batch language and full string functionality being added by 1965. BASIC was first implemented on the GE-265 mainframe which supported multiple terminals. Contrary to popular belief, it was a compiled language at the time of its introduction. It was also quite efficient, beating FORTRAN II and ALGOL 60 implementations on the 265 at several fairly computationally intensive (at the time) programming problems such as numerical integration by Simpson's Rule.
The designers of the language decided to make the compiler available free of charge so that the language would become widespread. They also made it available to high schools in the Dartmouth area and put a considerable amount of effort into promoting the language. As a result, knowledge of BASIC became relatively widespread (for a computer language) and BASIC was implemented by a number of manufacturers, becoming fairly popular on newer minicomputers like the DEC PDP series and the Data General Nova. The BASIC language was also central to the HP Time-Shared BASIC system in the late 1960s and early 1970s. In these instances the language tended to be implemented as an interpreter, instead of (or in addition to) a compiler.
Several years after its release, highly-respected computer professionals, notably Edsger W. Dijkstra, expressed their opinions that the use of GOTO statements, which existed in many languages including BASIC, promoted poor programming practices. Some have also derided BASIC as too slow (most interpreted versions are slower than equivalent compiled versions) or too simple (many versions, especially for small computers left out important features and capabilities).
Notwithstanding the language's use on several minicomputers, it was the introduction of the MITS Altair 8800 "kit" microcomputer in 1975 that provided BASIC a path to universality. Most programming languages required more memory (and/or disk space) than was available on the small computers most users could afford. With the slow memory access that audio tapes provided and the lack of suitable text editors, a language like BASIC which could satisfy these constraints, as well as being interpreted line by line from a tape device, was attractive.
BASIC also had the advantage that it was fairly well known to the young designers and computer hobbyists who took an interest in microcomputers, and generally worked in the electronics industries of the day. Kemeny and Kurtz's earlier proselytizing paid off in this respect and the few hobbyists journals of the era were filled with columns that made mentions of the language or focused entirely on one version compared to others.
One of the first to appear for the 8080 machines like the Altair was Tiny BASIC, a simple BASIC implementation originally written by Dr. Li-Chen Wang, and then ported onto the Altair by Dennis Allison at the request of Bob Albrecht (who later founded Dr. Dobb's Journal). The Tiny BASIC design and the full source code were published in 1976 in DDJ.
In 1975, MITS released Altair BASIC, developed by college drop-outs Bill Gates and Paul Allen as the company Micro-Soft (who started today's corporate giant, Microsoft). The first Altair version was co-written by Gates, Allen and Monte Davidoff in a burst of enthusiasm and neglect of studies. Versions of Microsoft BASIC (also known then, and most widely as M BASIC or MBASIC, see sidebar) was soon bundled with the original floppy disk-based CP/M computers, which became widespread in small business applications. As the popularity of BASIC on CP/M spread, newer computer designs also introduced their own version of the language, or had Micro-Soft port version to their platform.
When three major new computers were introduced in what Byte Magazine would later call the "1977 Trinity", all three had BASIC as their primary programming language and operating environment. The Commodore PET licensed a version of Micro-Soft BASIC that was ported to the MOS 6502, while Apple II and TRS-80 both introduced new versions of the language that were largely similar. As new companies entered the field, additional versions were added that subtly changed the BASIC family. The Atari 8-bit family had their own Atari BASIC that was modified in order to fit on 8 kB ROM cartridge. The BBC published BBC BASIC, developed for them by Acorn Computers Ltd, incorporating many extra structuring keywords. Most of the home computers of the 1980s had a ROM-resident BASIC interpreter, allowing the machines to boot directly into BASIC. There are more dialects of BASIC than there are of any other programming language.
During this growth time for BASIC, many magazines were published such as Creative Computing Magazine that included complete source codes for games, utilities, and other programs. Given BASIC's straightforward nature, it was considered a simple matter to type in the code from the magazine and execute the program. Different magazines were published featuring programs for specific computers, though some BASIC programs were universal and could be input into any BASIC-using machine. A logical extension of the magazine idea was the publishing of BASIC source code in full-fledged books: probably the classic example was David Ahl's series of Basic Computer Games.
As early as 1979 Microsoft was in negotiations with IBM to supply them with a version of BASIC. Microsoft sold several versions of BASIC for MS-DOS/PC-DOS including BASICA, GW-BASIC (a BASICA-compatible version that did not need IBM's ROM) and QuickBASIC. Turbo Pascal-publisher Borland published Turbo BASIC 1.0 in 1985 (successor versions are still being marketed by the original author under the name PowerBASIC).
These languages introduced many extensions to the original home computer BASIC, such as improved string manipulation and graphics support, access to the file system and additional data types. More important were the facilities for structured programming, including additional control structures and proper subroutines supporting local variables.
However, by the latter half of the 1980s newer computers were far more capable with more resources. At the same time, computers had progressed from a hobbyist interest to tools used primarily for applications written by others, and programming became less important for most users. BASIC started to recede in importance, though numerous versions remained available. Compiled BASIC or CBASIC is still used in many IBM 4690 OS point of sale systems.
BASIC's fortunes reversed once again with the introduction of Visual Basic by Microsoft. It is somewhat difficult to consider this language to be BASIC, because of the major shift in its orientation towards an object-oriented and event-driven perspective. The only significant similarity to older BASIC dialects was familiar syntax. Syntax itself no longer "fully defined" the language, since much development was done using "drag and drop" methods without exposing all code for commonly-used objects such as buttons and scrollbars to the developer. While this could be considered an evolution of the language, few of the distinctive features of early Dartmouth BASIC, such as line numbers and the
INPUT keyword, remain (although Visual Basic still uses
INPUT to read data from files, and
INPUTBOX is available for direct user input; line numbers can also optionally be used in all VB versions, even VB.NET, albeit they cannot be used in certain places, for instance before
Ironically given the origin of BASIC as a "beginner's" language, and apparently even to the surprise of many at Microsoft who still initially marketed Visual Basic or "VB" as a language for hobbyists, the language had come into widespread use for small custom business applications shortly after the release of VB version 3.0, which is widely considered the first relatively stable version. While many advanced programmers still scoffed at its use, VB met the needs of small businesses efficiently wherever processing speed was less of a concern than easy development. (By that time, computers running Windows 3.1 had become fast enough that many business-related processes could be completed "in the blink of an eye" even using a "slow" language, as long as massive amounts of data were not involved.) Many small business owners found they could create their own small yet useful applications in a few evenings to meet their own specialized needs. Eventually, during the lengthy lifetime of VB3, knowledge of Visual Basic had become a marketable job skill.
Many BASIC dialects have also sprung up in the last few years, including Bywater BASIC and True BASIC (the direct successor to Dartmouth BASIC from a company controlled by Kurtz). Many other BASIC variants and adaptations have been written by hobbyists, equipment developers, and others, as it is a relatively simple language to develop translators for. An example of an open source interpreter, written in C, is MiniBasic
The ubiquity of BASIC interpreters on personal computers was such that textbooks once included simple "Try It In BASIC" exercises that encouraged students to experiment with mathematical and computational concepts on classroom or home computers. Futurist and sci-fi writer David Brin mourns the loss of ubiquitous BASIC in a recent Salon article.
The following example is in Visual Basic .NET: