Text I
History of Programming Languages
EXERCISE 1
Read and translate the text.
Like many "firsts" in history, the first modern programming language is hard to identify. The first programming languages predate the modern computer, they were codes. Jacquard looms and Charles Babbage's Difference Engine both had simple, extremely limited languages for describing the actions that those machines should perform. Data was encoded on punch cards.
In the 1940s 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.
Some important languages that were developed in this time period include ENIAC coding system (1943) and C-10 (1949).
In the 1950s the first three modern programming languages whose descendants are still in widespread use today were designed:
FORTRAN, the " FOR mula TRAN slator, invented by John W. Backus,
LISP, the " LIS t P rocessor", invented by John McCarthy,
COBOL, the CO mmon B usiness O riented L anguage, 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 " ALGO rithmic L anguage"). 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 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). Each of these languages spawned an entire family of descendants, and most modern languages count at least one of them in their ancestry.
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.
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.
The rapid growth of the Internet in the mid-1990's 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 (1991) rose to popularity because of its early integration with the Netscape Navigatorweb browser, and various scripting languages achieved widespread use in developing customized applications for web servers.
Programming language evolution continues, in both industry and research. There are 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: mixings, delegates, aspects;
· component-oriented software development;
· increased emphasis on distribution and mobility;
· integration with databases, including XML and relational databases.
EXERCISE 2