Transcript Introduction to Programming

Introduction to Programming
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Resource Team
R.P Ranjan-Lecturer, SPICTEC, Galle.
W.M.A.S . Wijesekara-Centre manager,CRC Hali-Ela
H.P.U.S Indra Kumara-Instructor,CRC Hanguranketha
R.M.P Bandara-Lecturer,CPICTEC Gurudeniya
K.M.P.U Wimalaweera-Instructor,CRC Polonnaruwa
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What is a computer program?
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A computer program is a set of instructions or
commands, which tell the computer what to do.
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A computer language is a set of symbols and rules
used in constructing programs.
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Computer languages are used to develop application
programs
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Cont….
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The machine can understand only the machine language.
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Assembly and other high level languages are not machine
language.
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To transform these languages into machine language, translators
are needed.
Source Code
Translator
Object Code
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Classification of Programming Languages
1st Generation
Low Level
Language
Computer
Language
2nd Generation
3rd Generation
High Level
Language
4th Generation
5th Generation
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Generation of programming languages

1st Generation language ( 1GL )
2nd
Generation languages( 2GL )
3rd
Generation languages ( 3GL )
4th
Generation languages ( 4GL )
5th
Generation languages ( 5GL )
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1st Generation language ( 1GL )
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Machine level programming language
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Machine code is the binary digit language
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It consists of 1s and 0s.
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The machine can directly execute the machine code
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Execution is speedy because no translators are used.
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It is very difficult to write and modify programs.
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It is machine dependant, because machine-language
instructions vary according to computer architecture.
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It is a low level language
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2nd Generation languages( 2GL )
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Assembly language is used
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Assembler is used to convert assembly language
to machine language
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Mnemonics and variables are used to write codes
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It is a machine dependant language
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Difficult to write and modify programs
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It is a low level language
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Execution is fast
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3rd Generation languages ( 3GL )
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It is easy to understand, because it is similar to human
languages
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Translators are used to convert high level language to
machine language
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Compilers or interpreters are used as translators.
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Some of the 3rd generation languages are unstructured
languages such as Basic
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It is easy write and modify programs
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3rd Generation languages ( 3GL )
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many of the third generation languages are procedural
languages because the program instructions comprise
a list of steps or procedures
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They are not machine dependent languages
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One instruction in a third generation language can
replace many assembly language instructions
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programmer has to describe how it should be done.
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Ex : Basic, Fortran, Cobol, Pascal
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4th Generation languages ( 4GL )
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Introduced in the late 1980s
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They are designed to reduce programming effort
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It consumes less time to write a program
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They are non procedural languages
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Very easy to write and modify
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One instruction in 4GL can replace a number of 3GL instructions
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Programmer has to describe what is to be done.
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4GL languages reduce software development cost.
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They are described as application development without
programmers
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Ex : FOCUS, IDEAL, dbase III plus
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5th Generation languages ( 5GL )
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Introduced in the early 1990s
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User-friendly Graphical User Interfaces are facilitated.
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Very easy to write and modify program
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Execution speed is low
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Event driven programs were introduced
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Ex: Visual basic, Visual C++, Small Talk
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Low Level Languages
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First and second generation languages are considered
low level languages.
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They are machine dependant languages
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These languages are close to the hardware
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The programmer should have hardware knowledge to
write a program
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Productivity is low
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High Level Languages
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3GL,4GL and 5GL are considered high level languages
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They are machine independent languages
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It is easy to write and modify
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The programmer does not need knowledge of
hardware to write programs
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Productivity is high
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Consume less time to write programs
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5GL allow user-friendly facilities
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Translators need to be used to convert to machine
language
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Translators
Translator is used to convert source code into object
code. these are of three types
1.
Assembler
2.
Interpreter
3.
Compiler
Source Code
Translator
Object Code
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Assembler
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is a low-level language Translator.
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is a software program that converts assembly
language into machine language.
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converts mnemonics into machine code
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Interpreter
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is a translator that goes through the process of
translation every time the program is run.
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is found running some versions of BASIC, where it
translates one line of the program at a time.
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Compiler
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is a translator of high level languages
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converts a whole program into machine language at
once
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translates source code into Object Code. This Object
code is used to execute whenever it is run
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Recompiling required if any changes of source code
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