The first programming languages predate the modern computer. Herman Hollerith (see Figure 1-6) realized that he could encode information on punch cards when he observed that railroad train conductors would encode the appearance of the ticket holders on the train tickets using the position of punched holes on the tickets. Hollerith then proceeded to encode the 1890 census data on punch cards which he made the same size as the boxes for holding US currency. (The dollar bill was later downsized.)
The first computer codes were specialized for the applications. In the first decades of the twentieth century, numerical calculations were based on decimal numbers. Eventually it was realized that logic could be represented with numbers, as well as with words. For example, Alonzo Church was able to express the lambda calculus in a formulaic way. The Turing machine was an abstraction of the operation of a tape-marking machine, for example, in use at the telephone conference calling companies. However, unlike the lambda calculus, Turing's code does not serve well as a basis for higher-level languages - its principal use is in rigorous analyses of algorithmic complexity.
Like many "firsts" in history, the first modern programming language is hard to identify. From the start, the restrictions of the hardware defined the language. Punch cards allowed 80 columns, but some of the columns had to be used for a sorting number on each card. Fortran included some keywords that were the same as English words, such as "IF", "GOTO" (go to) and "CONTINUE". The use of a magnetic drum for memory meant that computer programs also had to be interleaved with the rotations of the drum. Thus the programs were more hardware dependent than today.
To some people the answer depends on how much power and human-readability is required before the status of "programming language" is granted. Jacquard looms and Charles Babbage's Difference Engine both had simple, extremely limited languages for describing the actions that these machines should perform. One can even regard the punch holes on a player piano scroll as a limited domain-specific programming language, albeit not designed for human consumption.
In the 1940s the first recognizably modern, electrically powered computers were created. The limited speed and memory capacity forced programmers to write hand tuned assembly language programs. It was soon discovered that programming in assembly language required a great deal of intellectual effort and was error-prone.
In 1945, Konrad Zuse published details of his programming language Plankalk�l. However, it was not implemented in his time and his original contributions were isolated from other developments because Germany was isolated during the war.
Some important languages that were developed in this time period include:
� 1943 - Plankalk�l (Konrad Zuse)
� 1943 - ENIAC coding system
� 1949 - C-10
In the 1950s the first three modern programming languages, whose descendants are still in widespread use today, were designed:
� FORTRAN, the "FORmula TRANslator", invented by John W. Backus et al.
� LISP, the "LISt Processor", invented by John McCarthy et al.
� COBOL, the COmmon Business Oriented Language, created by the Short Range Committee, heavily influenced by Grace Hopper
Another milestone in the late 1950s was the publication, by a committee of American and European computer scientists, of "a new language for algorithms"; the Algol 60 Report (the "ALGOrithmic Language"). This report consolidated many ideas circulating at the time and featured two key innovations:
� The use of Backus-Naur Form (BNF) for describing the language's syntax. Nearly all subsequent programming languages have used a variant of BNF to describe the context-free portion of their syntax.
� The introduction of lexical scoping for names in arbitrarily nested scopes.
Algol 60 was particularly influential in the design of later languages, some of which soon became more popular. The Burroughs B5000 was designed to be programmed in an extended subset of Algol.
Some important languages that were developed in this time period include:
� 1951 - Regional Assembly Language
� 1952 - Autocode
� 1954 - FORTRAN
� 1958 - LISP
� 1958 - ALGOL
� 1959 - COBOL
� 1962 - APL
� 1962 - Simula
� 1964 - BASIC
� 1964 - PL/I
The period from the late 1960s to the late 1970s brought a major flowering of programming languages. Most of the major language paradigms now in use were invented in this period:
� Simula, invented in the late 1960s by Nygaard and Dahl as a superset of Algol 60, was the first language designed to support object-oriented programming. Smalltalk (mid 1970s) provided a complete ground-up design of an object-oriented language.
� C, an early systems programming language, was developed by Dennis Ritchie and Ken Thompson at Bell Labs between 1969 and 1973.
� Prolog, designed in 1972 by Colmerauer, Roussel, and Kowalski, was the first logic programming language.
� ML built a polymorphic type system (invented by Robin Milner in 1978) on top of Lisp, pioneering statically typed functional programming languages.
Each of these languages spawned an entire family of descendants, and most modern languages count at least one of them in their ancestry.
The 1960s and 1970s also saw considerable debate over the merits of "structured programming", which essentially meant programming without the use of GOTO. This debate was closely related to language design: some languages did not include GOTO, which forced structured programming on the programmer. Although the debate raged hotly at the time, nearly all programmers now agree that, even in languages that provide GOTO, it is bad style to use it except in rare circumstances. As a result, later generations of language designers have found the structured programming debate tedious and even bewildering.
Some important languages that were developed in this time period include:
The 1980s were years of relative consolidation. C++ combined object-oriented and systems programming. The United States government standardized Ada, a systems programming language intended for use by defense contractors. In Japan and elsewhere, vast sums were spent investigating so-called "fifth generation" languages that incorporated logic programming constructs. The functional languages community moved to standardize ML and Lisp. Rather than inventing new paradigms, all of these movements elaborated upon the ideas invented in the previous decade.
However, one important new trend in language design was an increased focus on programming for large-scale systems through the use of modules, or large-scale organizational units of code. Modula, Ada, and ML all developed notable module systems in the 1980s. Module systems were often wedded to generic programming constructs - generics being, in essence, parameterized modules.
Although major new paradigms for programming languages did not appear, many researchers expanded on the ideas of prior languages and adapted them to new contexts. For example, the languages of the Argus and Emerald systems adapted object-oriented programming to distributed systems.
The 1980s also brought advances in programming language implementation. The RISC movement in computer architecture postulated that hardware should be designed for compilers rather than for human assembly programmers. Aided by processor speed improvements that enabled increasingly aggressive compilation techniques, the RISC movement sparked greater interest in compilation technology for high-level languages.
Language technology continued along these lines well into the 1990s. However, the adoption of languages has always been driven by the adoption of new computer systems, and in the mid-1990s one of the most important new systems in computer history suddenly exploded in popularity.
Some important languages that were developed in this time period include:
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The rapid growth of the Internet in the mid-1990s was the next major historic event in programming languages. By opening up a radically new platform for computer systems, the Internet created an opportunity for new languages to be adopted. In particular, the Java programming language rose to popularity because of its early integration with the Netscape Navigator web browser, and various scripting languages achieved widespread use in developing customized applications for web servers. Many computer information systems degree courses today teach Java as well as other programming languages. Neither of these developments represented much fundamental novelty in language design; for example, the design of Java was a more conservative version of ideas explored many years earlier in the Smalltalk community, but the widespread adoption of languages that supported features like garbage collection and strong static typing was a major change in programming practice.
Some important languages that were developed in this time period include:
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Programming language evolution continues in both industry and research, and is used in industries ranging from security cameras to televisions. Some current directions:
� Mechanisms for adding security and reliability verification to the language: extended static checking, information flow control, static thread safety.
� Alternative mechanisms for modularity: mixins, delegates, aspects.
� Component-oriented software development.
� Increased emphasis on distribution and mobility.
� Integration with databases, including XML and relational databases.
� Open Source as a developmental philosophy for languages, including recent languages such as Python, Ruby, and Squeak.
� Support for Unicode so that source code (program text) is not restricted to those characters contained in the ASCII character set; allowing, for example, use of non-Latin-based scripts or extended punctuation.
Some important languages developed during this period include:
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