Add questions, from this LM, to the FPE?

MAJOR UPDATE: 12/8/99; LAST UPDATE: 12/9/06
Currently under REconstruction
This is the most current version of Learning Module IX; however, the FIB/SAQ/TPQ tools have yet to be included.
Also the study guide needs to be written (for the independent learner) and
some of the content sections, links, and assessment tools need to be fine-tuned.  (Nothing is wrong, just imperfect!)
Note that the blinking text designates things that I need to work on; the material is not wrong, but can be improved.
(Don't worry, I don't like blinking text, either, so there will not be any in the finished product!)

LEARNING MODULE X:
SURVEY OF PROGRAMMING LANGUAGES

        Computer languages are software (translators) that allow a user to communicate instructions to a computer system; in particular, computer languages allow the user to write application programs. Numerous languages have been developed to facilitate the translation of human algorithms into machine language programs that a computer can execute.  Independent learners should read the objectives and sequence of presentations, summary, then the Study Guide for this learning module {NOT WRITTEN YET}.

The Objectives of this learning module are:

1. introduce the basic concepts of computer programming languages,
2. to distinguish the characteristics of, and illustrate the differences between, low level, high level, and very high level programming languages,
3. to distinguish structured programming languages and object oriented programming languages, and
4. to survey the most important programming languages based on popularity and currency.

The sequence of presentations in this learning module is as follows.  You can click on any link to jump directly to that section.

1. PROGRAMMING LANGUAGE LEVELS
2. COMPARISON OF THE LANGUAGE LEVELS
3. STRUCTURED PROGRAMMING LANGUAGES
4. OBJECT-ORIENTED PROGRAMMING LANGUAGES
5. SURVEY OF POPULAR HIGH-LEVEL LANGUAGES
6. SURVEY OF SOME NEWER LANGUAGES
7. SUMMARY {NOT WRITTEN YET}

1. PROGRAMMING LANGUAGE LEVELS:

        Programming languages have two primary components (1) a set of built-in language primitives (words that represent data types, control structures, modularization constructs, etc. and symbols that represent math or logical operations) that may be combined into programs and (2) a translator (assemblers, compilers, or interpreters) that transforms source code (written in the programming language) into object code (machine language equivalent). There are three (at least) categories of programming languages:

1.1 Low Level Languages are "computer oriented":
 

1. Low Level Languages = computer oriented languages, i.e. they directly manipulate hardware. Each language is unique to the CPU on which it is implemented and is, therefore, not portable (i.e. not usable on a computer with a different CPU).
2. There are two categories of low level languages:
1. Machine Language (ML)= binary, octal, hex, etc. code; non-binary code is translated into binary code that is directly executable by the computer. Each instruction corresponds to a machine operation, part of the instruction set characteristic of the CPU. Now machine language is virtually never used by humans.  See the right hand column of the table in section 2.
   
2. Assembly Language (AL) = mnemonic (abbreviated English words) instructions with a one-to-one correspondence with machine language instructions; translated into ML by an assembler. Assembly language, being machine oriented,is faster and more efficient in the use of hardware than HLL or VHLL.  See the middle column of the table in section 2.

1.2 High-level Languages (HLL) are "developer oriented", i.e. tools of software developers:

1. The words and grammar of HLL are English-like. A HLL language is governed by a strict syntax (set of grammatical rules); if this is standardized, the language is portable (can be used on different computer systems).
2. HLL reflect the logic and procedures used in a human algorithm. Thus HLL programming is "task-oriented" rather than "machine oriented"; the programmer is able to concentrate on developing task algorithms rather than on how the computer will carry out the instructions. However, the programmer must still specify a complete set of detailed instructions.C. HLL programs are translated into ML by either compilers or interpreters. Most HLL instructions translate into multiple ML instructions.
3. HLL have two distinct subcategories (different "paradigms"):
1. Procedural languages (imperative paradigm), by far the most common, require a complete algorithm to be specified.
   
1. Such languages typically use procedures to modularize programs, use loops to implement repetition, and use arrays and records to build more advanced data structures. 
   
2. They are typically used in sience and business applications.
3. Examples include Java, C, C++, C#, Pascal, Modula, Ada, etc.
   
2. Functional languages (declarative paradigm) require that an operation be defined instead of its algorithm being specified.
   
1. They typically use functions to modularize programs, recursion to implement repetition, and use lists to build user-defined data structures. Lisp and Logo are examples of functional languages; Prolog is an example of a relational language, a relative of functional languages. 
   
2. They are typically used in artificial intelligence and expert systems applications.
3. Example include Logo, Lisp, and Prolog.
   

        VHLL are very new and are still evolutionary. Consequently there is disagreement over terminology at present. The text confuses VHLL with "4GLs" which are, according to conventional thinking, a subset of VHLL. Therefore, when reading the text, replace "4GL" with 'VHLL".

1. VHLL are similar to HLL except they are more sophisticated and easier to learn and use because many powerful primitives are built into the languages. One goal of VHLL is to give nonprogrammers the ability to create simple computer applications.
2. The translation software performs most of the details involved with handling information processing tasks. The commands require only that the programmer specify what tasks are to be performed. This automation, however, removes a much control from the hands of the programmer.
3. VHLL are "special purpose languages", (often associated with specific software packages like a DBMS), and thus have have limited range of application, within which they are very powerful. This power and ease of use must be balanced by the sacrifices in control over the processing details and access to computer hardware. As long as the task fits the narrow capabilities of a VHLL, coding proceeds quickly and smoothly.
4. There is little standardization in current VHLL (they are usually intimately associated to a particular type of hardware or software). This results in a lack of portability which has restricted their current popularity. This is changing rapidly.
5. Examples of VHLL:
1. Forth Generation Languages (4GLs) are VHLL associated with DBMS that facilitate the manipulation of the language in powerful, user-defined ways in order to develop management-oriented applications. 4GL tools include:
1. report generators, such as RPG,
2. retrieval/update languages such as SQL (Rarely actually called a 4GL.)
3. decision support systems,
4. graphics generators, and
5. application generators that facilitate custom-made applications within the domain of the DBMS.
2. Authoring systems  are VHLL designed to allow nonprogrammers to create Multimedia (text, graphics, animation, audio, and video) applications. These have greater potential for developing individualized learning system software. (For more details see the presentation in COSC120.)
   
1. Currently, Hypertext Markup Language (HTML) is used to author World Wide Web pages.
   
2. Extensible Markup Language (XML), a platform-independent Web document formatting language, is an improvement on HTML.  XML is "extensible" because, unlike HTML, the ability to define new markup tags makes it virtually unlimited and self-defining.
   
3. SMIL (Synchronized Multimedia Integration Language), pronounced "smile", was  designed to facilitate the definition of and synchronization of streaming multimedia elements (video, sound, still images)
4. Virtual Reality Modeling Language (VRML) is used to add 3D environments to Web pages that can be "explored" and with which the user can interacted; VRML can be "plugged into" HTML programs.
3. Scripting languages are designed to help nonprogrammers customize applications or create simple applications, e.g. JavaScript allows users to liven up their Web pages.

1. Comparison by Code Format: The following examples give the code for the simple assignment instruction, Sum ¨ X + Y, i.e. adding the values in variables X and Y and then storing their sum in the variable Sum.

 

HLL Instruction (Pascal):	Equivalent Assembly Language Instructions:	Equivalent Machine Language Instructions (Hex; Binary):
Sum := X + Y ;	LDA A X	B6 0300; 101101100000001100000000
	ADD A Y	BB 0301; 101110110000001100000001
	STA A S	B7 0302; 101101110000001100000010

1. The Assembly and Machine language instructions are:
1. load the accumulator (A) with the contents of X (only the machine language specifies the memory location, 300),
2. add the contents of Y (301) to the Contents of the accumulator, and
3. store the contents of the accumulator at S (302).
2. Note that ML and AL have instruction sets that are strictly CPU dependent; those in the table above are for the Motorola 6800 microprocessor. In the Intel 8080 instruction set, where addition can only occur within registers (not the accumulator), the AL instructions would be:

2. It is somewhat surprising (and frustrating) to find the same instruction, in different languages, is different, sometimes VERY different!  Examples of the assignment statement in other high level languages include:

      According to FOLDOC, "A structured programming language is one in which a program may be broken down into blocks or procedures which can be written without detailed knowledge of the inner workings of other blocks, thus allowing a top-down design approach. For a discussion of structure programming see section 3 of LM IX, Software Development.

1. Techniques that impose a logical structure on the writing of a program.
1. Large programs are broken down into smaller modules (called procedures or functions).
2. Algorithms are defined in terms of three structured constructs:
1. sequence, the default execution is one instruction after another unless modified by selection or repetition constructs,
2. selection (IF-THE-ELSE) allows a logical expression to select one of two alternative blocks of code to execute,
3. repetition (WHILE, or REPEAT-UNTIL loops or recursion) allows a logical expression to govern the repetition of a block of code.
2. To make programs more readable, each statement occupies only one line and blocks of code in selection or repetition blocks are indented.
3. Structured languages (e.g. Pascal and Ada) and object oriented languages (e.g. C++ and Java) force the programmer to write structured programs. However, unstructured languages such as older versions of FORTRAN, COBOL and BASIC require discipline on the part of the programmer."

4.  OBJECT-ORIENTED PROGRAMMING LANGUAGES:

        Object oriented programming languages allows software developers to construct programs as if they are collections of self-contained "components".  The fundamental component is the class which is a template from which actual objects can be created (called "instantiation").    The class (and consequently any object instantiated from it) are completely defined by the attributes that define its state and methods that define its behaviour.   For a discussion of OOP see section 4 of the Software Development learning module.   Smalltalk was the first purely object-oriented language, but object-oriented extensions have been added to many existing languages resulting in "hybrid" languages such as C++, Object Pascal, Ada 95, CLOS (object oriented Lisp), Object Logo, Prolog++, etc.  (Some of these are briefly described in the following section.)  Java, the fastest growing language in popularity (particularly for distributed systems like the Internet) is a purely object oriented programming language based on Smalltalk but with a syntax similar to C++.  (See below.)

5. SURVEY OF POPULAR HIGH-LEVEL LANGUAGES:

1. FORTRAN (1954-57): Stands for FORmula TRANslation. First HLL programming language. Developed by IBM. Main use in science and engineering.
2. COBOL (1958-60): Stands for COmmon Business Oriented Language. Developed by Department of Defense as a simple, standardized, portable language for writing business programs that are easily maintained.
3. LISP (1956-62): Stands for LISt Processing. Developed at MIT to develop AI (Artificial Intelligence) programming. Still the dominant language for AI in the U.S.A. Although it is basically a functional language based on recursion, several dialects augment LISP with nonfunctional features.
4. BASIC (1965) : Stands for Beginner's All-purpose Symbolic Instruction Code. Developed as an interpreted language that was easy to learn and use. The relatively small and inexpensive interpreters and compilers caused it to be the language of choice for early microcomputers, most of which came "bundled" with BASIC. Visual Basic is an object-oriented extension of BASIC that has a user-friendly GUI development system.
5. Pascal (1971): Developed by Nicholas Werth to facilitate teaching structured programming. The standard teaching language world wide. Its success has resulted in its being extended for use as a general purpose programming language, something for which it was not designed.

1. Ada (1979) : Ada, a very powerful, complex language, was developed by the Department of Defense for general purpose programming. Its sophisticated control structures and data structures also make it ideal for embedded applications (e.g. weapons systems) and real-time applications. Ada 95 is a superset of Ada that incorporates OOP features.
2. C (1974), C++, and C#: C, developed for writing system software, is a "mid-level language" in that it has AL features and is more machine-oriented than HLL. Thus it can run faster than typical HLL and is an alternative to hard-to-develop, CPU-specific assembly languages. It was very popular with professional software developers, but has now been virtually replaced by C++, an extension of the language that provides OOP facilities, thus producing a "hybrid language". Both C and C++ code can be very cryptic and hard to understand.  C# is the newest of this family of languages.
   
3. Logo (1968, 1976): Logo was developed at MIT, as a "user-friendly version of LISP, to facilitate learning math concepts. It has become the language of choice for introducing programming, via "turtle graphics", to elementary school children. However its huge success at this has led to its underestimation as a language for other applications; in fact, many believed it is the most underrated of all programming languages. It is billed as a "complete learning environment" where exploration is the guiding principle.
4. PROLOG (1970): Based firmly on the principles of logic, it rivals LISP as the language of choice for AI programming. It has been chosen as the basic language for the "Fifth Generation of Computers" being built by the Japanese.
5. HyperTalk(1987): Hypertalkis a VHLL contained within "Hypercard", Apple's object oriented programming environment that is called " a soft-ware erector set for non programmers" . Hypertalk is Apple's implementation of Hypermedia, a VHLL language concept for handling information in all forms (data, text, graphics, animation, audio, and video). It is billed as the "language for the rest of us" in that it can be used by nonprogrammers to unleash the power of the computer.
6. Smalltalk (1974-1980): Smalltalk was the first purely object-oriented programming (OOP) language; it extends the ideas of structured programming to more human oriented viewpoints involving objects which respond to messages sent to them by the computer system under the direction of the user. Many say that Smalltalk is the prototype of the programming paradigm of the future, OOP.
7. Java (1991-today): Java is a purely OO, procedural, HLL designed to facilitate reliable, platform-independent, distributed processing. It has become "the" development language for Internet and intranet applications because Java "applets" (special programs) can be called directly from HTML.
1. Java is the the language of choice for most computer science curricula, including that at FSU.
2. The reliability goal means it was designed to be secure (hacker resistant) and robust (bug resistant); its platform-independence means it is independent of the CPU and OS on which it is used.
8. JavaScript is a VHLL that is a simplified version of Java, specifically designed to add scripts (embedded programs) in HTML documents, especially to provide dynamic capabilities to Web pages; see HTML, below.
1. Personally I think that JavaScript is perhaps the best language for beginners to learn; see the reasons JavaScript is the best language to begin learning object oriented software developement (OOSD) in the Study Guide to LMVII of COSC330.  JavaScript is very lenient about syntax, compared to many programming languages, which makes it more USER FRIENDLY (especially for beginners),
2. If you are only interested in learning JavaScript, click on the JavaScript Thread of COSC330.
   
9. Hypertext Markup Language (HTML) is the VHLL used to create Web pages. It is really only a collection of tags which, when incerted into regular text, tell a Web browser how to:
1. format text,
2. incert an image, video clip, or sound into a Web page,
3. link to another location in the page or another Web page, even on another computer (server) or
4. link to other programs written in VRML, TVML, Java, JavaScript, or other languages.