Objective: To learn meaning and concepts of programming. Outcome: By the end of this students should be able to describe the meaning of programming

Transcription

1 30 th September 2018

2 Objective: To learn meaning and concepts of programming Outcome: By the end of this students should be able to describe the meaning of programming

3 Section 1: What is a programming language? Section 2: Why many programming languages? Section 3: Types of programming languages? Section 4: Does the world need new languages? Section 5: Learn your first language( mama ) html Section 6: Review Questions Next week-3: Unit 1B Content Precursor

4 A programming language is a set of rules that provides a way of telling a computer what operations to perform. A programming language is a set of rules for communicating an algorithm. It provides a linguistic framework for describing computations.

5 A programming language is a notational system for describing computation in a machine-readable and human-readable form. A programming language is a tool for developing executable models for a class of problem domains.

6 English is a natural language. It has words, symbols and grammatical rules. A programming language also has words, symbols and grammatical rules. The grammatical rules are called syntax. Each programming language has a different set of syntax rules; same way as natural language thus..

7 d a L o v e l a c e N a m e : B o r n A u g u s t a A d a B y r o n, A d a L o v e l a c e w a s a l s o k n o w n as A u g u s t a A d a K i n g and the C o u n t e s s of L o v e l a c e. B o r n : D e c e m b e r 10, 1815 in L o n d o n D e a t h : N o v e m b e r 27, 1852 ( A g e : 36) C o m p u t e r r e l a t e d c o n t r i b u t i o n s S h e is c r e d i t e d as b e i n g t h e w o r l d s f i r s t c o m p u t e r p r o g r a m m e r. D e v e l o p e d t h e f i r s t a l g o r i t h m to be p r o c e s s e d by a m a c h i n e. H e l p e d C h a r l e s B a b b a g e w i t h h i s a n a l y t i c a l e n g i n e. P u b l i c a t i o n s S k e t c h of t h e A n a l y t i c a l E n g i n e I n v e n t e d by C h a r l e s B a b b a g e R e l a t e d c o m p u t e r p i o n e e r s C h a r l e s B a b b a g e

8 Programming languages have evolved over time as better ways have been developed Popularity of programming languages picked up in 1950s Since then thousands of languages have been developed Different programming languages are designed for different types of programs & purpose.

9 High-level programs (e.g. English writin gclass Triangle { (3 rd 4th, 5 th, nth GenerationsLanguages)... float surface() return b*h/2; } Low-level program (e.g. English Translation) (2 nd Generation/Assembly Language) Executable Machine code (e.g. Maths) (1 st Generation Machine Language) LOAD r1,b LOAD r2,h MUL r1,r2 DIV r1,#2 RET

10 First Generation Languages Machine Language Second Generation Languages-Assembly Language Third Generation Languages High Level Language Fourth Generation Languages-Problem-oriented Fifth Generation Languages -Close to Natural Language n th /Future Generation Language- Plug & play Expected

11 Machine language (0 and 1) Operation code such as addition or subtraction. Operands It identifies the data to be processed. Machine language is machine dependent as it is the only language the computer can understand. challenges Very efficient code but difficult to write. Not user friendly; even for top mathematicians

12 Translators/Assembly languages Introduces mathematics symbols/ operation codes (2 nd GL introduces symbols #, * ; %, () {} [] <> C/:) Each assembly language instruction is translated into one machine language instruction. Very efficient code and easier to write. Types of Translators are: Interpreter, Assembler and compiler (NB: refer to slide 15)

13 Closer to English but included simple mathematical notation (syntax) for computer translators to understand and translate meaning to machine language level for execution. Programs written in source code (closer to English/natural expressions) must be translated into machine language; also called object code ( 0&1 codes defined internally for the computers); through the translators ( middle-man ).

14 Alternative to compilation ( by system compiler program ) is interpretation which is accomplished by a system program called an interpreter. Common third generation languages FORTRAN COBOL C and C + + Visual Basic

15 3 rd, 4 th 5 th Generation/High level languages Allows Programmer to write natural English language Purpose 1 2 nd Generation/ Assembly Languages Purpose 2 purpose 3 ASSEMBLER (OS) Focus to translate Symbols in 3 rd G for 1G to execute INTERPRETER (VBIDE) Alert errors at coding time Translate Alpha & Numeric COMPILER (C++ IDE) Alert errors at run time. Translates Alpha & Numeric 1 st Generation/ Low level /Machine Language Understands 0 and 1 bits only Nb: Ideally, installed IDE is the interpreter/compiler

16 Another high level language having fewer instructions (syntax) to accomplish a task than a third generation language. Most of the routine syntax required are automatically embedded for easy/friendly programming and reduce time spent for coding. Used with Databases Query languages (Structured Query Languages-SQL) Report generators Forms designers Application generators

17 Provides icons, menus, drawing tools (object oriented (e.g. VB, python, Ruby, Visual C++ etc. ) (More functions are visually represented as object Click & Declare) Declarative languages Functional(?): Lisp, Scheme, SML Also called applicative Everything is a function Logic: Prolog Based on mathematical logic Rule- or Constraint-based

18 Though no clear definition at present Ongoing proposal and expectation for programs where user only state their problem and get things done (plug & Play) 5 th generation has Limited capabilities at present and thus require some further works in the software engineering world.

19 Do you have to learn every language A-Z? NO! E.g. American English vrs British English)

20 Imperative Programming (C) Object-Oriented Programming (C++) Logic/Declarative Programming (Prolog) Functional/Applicative Programming (Lisp)

21 Two broad groups Traditional programming languages Sequences of instructions First, second and some third generation languages Object-oriented languages Easy Approach (visual clicks Objects are created rather than sequences of instructions Some third generation, and fourth and fifth generation languages Types: see page 22

22 Type: FORTRAN FORmula TRANslation. Developed at IBM in the mid-1950s. Designed for scientific and mathematical applications by scientists and engineers.

23 Type 2: COBOL COmmon Business Oriented Language. Developed in Designed to be common to many different computers. Typically used for business applications.

24 Type 3: BASIC Beginner s All-purpose Symbolic Instruction Code. Developed at Dartmouth College in mid 1960s. Developed as a simple language for students to write programs with which they could interact through terminals.

25 Type 4: C Developed by Bell Laboratories in the early 1970s. Provides control and efficiency of assembly language while having third generation language features. Application: Often used for hardware/system program. UNIX OS is written in C.

26 Type 1: Simula First object-oriented language Developed by Ole Johan Dahl in the 1960s. Type 2: Smalltalk First purely object-oriented language. Developed by Xerox in mid-1970s. Still in use on some computers.

27 Type 3: C++ It is C language with additional features. Widely used for developing system and application software. Graphical user interfaces can be developed easily with visual programming tools.

28 Type 4: JAVA An object-oriented language similar to C + + that eliminates lots of C ++ s problematic features Allows a web page developer to create programs for applications, called applets that can be used through a browser. Objective of JAVA developers was to have languge very independent to run on any machine, platform or operating system.

29 Scripting Languages (Websites) JavaScript and VBScript Php and ASP Perl and Python Command Languages sh, csh, bash Text processing Languages (Journals) LaTex, PostScript

30 HTML HyperText Markup Language. Used on the Internet and the World Wide Web (WWW). Web page developers puts brief codes called tags in the page to indicate how the page should be formatted.

31 XML Extensible Markup Language. A language for defining other languages.

32 When it comes to mechanics of the task, learning to speak and using programming languages are in many ways like learning to speak a human language Both languages require a user to learn new vocabulary, syntax and semantics (new words, sentence structure and meaning) Both languages require considerable practice into perfection.

33 Computer languages lack ambiguity and vagueness. (rules of the language are restrictive) Unlike English sentences such as I saw the man with a telescope (Who has the telescope?) or Take a pinch of salt (How much is a pinch?) In a programming language, a sentence has one meaning (restrictive) or otherwise meaningless. Garbage in garbage out.

34 Run-time performance Life cycle (human) cost is more important e.g. Ease coding Efficient debugging Quick Maintenance

35 Writability: The quality of a language that enables a programmer to use it to express a computation clearly, correctly, concisely, and quickly. Readability: The quality of a language that enables a programmer to understand and comprehend the nature of a computation easily and accurately. Orthogonality: The quality of a language that features provided have as few restrictions as possible and be combinable in any meaningful way. Reliability: The quality of a language that assures that a program will not behave in unexpected or disastrous ways during execution. Maintainability: The quality of a language that reduces errors. It can be found and corrected and new features can also be added.

36 Generality: The quality of a language that avoids special cases in the availability or use of constructs and by combining closely related constructs into a single more general one. Uniformity: The quality of a language that states; similar features should look similar and behave similar. Extensibility: The quality of a language that provides some general mechanism for the user to add new constructs to a language. Standardability: The quality of a language that allows programs written to be transported from one computer to another without significant change in language structure. Implementability: The quality of a language that enables a translator or interpreter to be can be written. This can address to complexity of the language definition.

37 1 st generation 2 nd generation 3 rd generation 4 th generation 5 th generation What determines a good language Criteria for good language design (W.R.O.R.M.G.U.E.S.I.)

38 w3 school html package.com A4 sheet start Show only text in my body Heading of my content Story Content First Paragraph Story content - free <html> <body> < h 1 > THE STORY OF MY LIFE-JULIET</h1> My name is Eric. I come from Aburi.. < p > < / p > When I leave school I will be a programmer I may travel to America to advance IT skills Body closed A4 sheet limit close < / body> < / h t m l > 1. create project 1folder. Keep all images and resources to display in that folder. 2. save notepad as Eric.html

39 Programming set of Rules 1. Sequence 2. Selection 3. Iteration 4. Read Recommended book before class

40 Thank you