cmpe13cyrus bazeghi 1 programming languages telling computers what to do

CMPE13 Cyrus Bazeghi1

Programming Languages

Telling computers what to do

CMPE13 2

Objectives

• Describe what programmers do and do not do

• Explain how programmers define a problem, plan the solution and then code, test, and document the program

• List and describe the levels of programming languages – machine, assembly, high level, very high level, and natural

• Describe the major programming languages in use today

• Explain the concepts of object-oriented programming

CMPE13

Program

Set of instructions written in a programming language that tells the computer what to do

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Programmers• Prepare instructions that make up the

program• Run the instructions to see if they

produce the correct results• Make corrections• Document the program• Interact with

– Users– Managers– Systems analysts

• Coordinate with other programmers to build a complete system

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The Programming Process

• Defining the problem• Planning the solution• Coding the program• Testing the program• Documenting the program

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The Programming Process: Defining the Problem

• What is the input• What output do you expect• How do you get from the input to

the output

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The Programming Process: Planning the Solution• Algorithms

– Detailed solutions to a given problem• Sorting records, adding sums of numbers,

etc..

• Design tools– Flowchart– Pseudocode

• Has logic structure, but no command syntax

• Desk-checking– Personal code design walk through

• Peer Reviews– “Code walk through”/structured walk

through

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The Programming Process: Planning the Solution

Accept series of numbers and display the average

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The Programming Process: Coding the Program

• Translate algorithm into a formal programming language

• Within syntax of the language• How to key in the statements?

– Text editor– Programming environment

• Interactive Development Environment (IDE)

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VI

• Mode editor, comes with pretty much all UNIX/LINUX distros

• Insert or command modes• Cheat Sheet

http://www.lagmonster.org/docs/vi.html

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Emacs

• A very “rich” editor• More than just an editor• Cheat Sheet

http://ccrma.stanford.edu/guides/package/emacs/emacs.html

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The Programming Process: Testing the Program

• Translation – compiler– Translates from source module into object

module– Detects syntax errors

• Link – linkage editor (linker)– Combines object module with libraries to

create load module– Finds undefined external references

• Debugging– Run using data that tests all statements– Logic errors

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The Programming Process: Documenting the Program

• Performed throughout the development• Material generated during each step

– Problem definitions– Program plan– Comments within source code– Testing procedures– Narrative– Layouts of input and output– Program listing

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Choosing a Language

• Choice made for you– What is available?– Required interface

• What do you know best?• Which language lends itself to the

problem to be solved?

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Language Generations

• Low levels closer to binary• High levels closer to human

code• Five Generations:

– Procedural Languages• Machine language• Assembly language• High-level language – 3GL

– Nonprocedural Languages• Very high-level language – 4GL• Natural language – 5GL

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Machine Language

• Written in strings of 0 and 1– Displayed as hexadecimal

• Only language the computer understands

• All other programming languages are translated to machine language

• Computer dependent

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Assembly Language

• Mnemonic codes– Add, sub, tst, jmp…

• Names for memory locations• Computer dependent• “Assembler” translates from

Assembly to machine language

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3GL: High-Level Languages

• 1960s• Languages designed for specific

types of problems and used syntax familiar to the people in that field– FORTRAN: (FORmula TRANslator)

• Math

– COBOL: (COmmon Business Oriented Language)• Business

• Compile translates from high-level language to machine language

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4GL: Very High-Level Languages

• Programmer specifies the desired results; the language develops the solution

• Ten times more productive with a 4GL than a procedural language

• Query Languages– Retrieve information from databases– Easy to learn and use

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5GL: Natural Languages

• Resemble natural or spoken English

• Translates human instructions into code the computer can execute

• Commonly used by non-programmers to access databases

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Third Generation Languages: Traditional

Programming

• Describe data• Describe procedures or

operations on that data• Data and procedures are separate

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Third Generation Languages

• FORTRAN– 1954– Represent complex mathematical

formulas– C/C++ has replaced FORTRAN

• COBOL– 1959– Business– Large complex data files– Formatted business reports

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Average a list of numbers

Accept series of numbers and display the average

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Third Generation Languages

FORTRAN

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Third Generation Languages

COBOL

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Third Generation Languages

• BASIC (Beginners All-purpose Symbolic Instruction Code)– 1965– Popularity grew with PC popularity

(1970s)– Easy to learn– Used little memory– Bill Gates beginnings.. MS Basic

• RPG– 1965– Report generation – quickly creates

complex reports

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Third Generation Languages

BASIC

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Third Generation Languages

• MS Visual Basic– 1987– Create complex user interfaces– Uses standard Windows features– Event-driven – user controls the

program

• C– 1972– Efficient code – the language of UNIX– Portability

• C++– Enhancement of C (Object Oriented)

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Third Generation Languages

C++

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OOP: Object-Oriented Programming

• Object– Self-contained unit of data and instructions– Includes

• Related facts (data)• Related functions (instructions to act on that data)

• Example– Object: cat– Data: feet, nose, fur, tail– Functions: eat, purr, scratch, walk– Cat: Kitty, Tabby

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OOP: Object-Oriented Programming

• Encapsulation – describes the objects self- containment

• Attributes – the facts that describe the object

• Methods / operations – the instructions that tell the object what to do

• Instance – one occurrence of an object• Messages – activate methods

– Polymorphism

Example: A ‘walk’ message causes Kitty to move (in a cat-like way)

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OOP: Object-Oriented Programming

• Class – defines characteristics unique to all objects of that class

• Inheritance – Objects of a class automatically posses all of the characteristics of the class from which it was derived

• Subclass – inherits characteristics from class and defines additional characteristics that are unique

• Instance – actual occurrence of an object

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ExampleClass: BoatSubclass: CanoeSubclass: PowerboatSubclass: SailboatInstance: Chardonnay II

OOP: Object-Oriented Programming

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OOP: Object-Oriented Programming

Using Objects in BusinessClass: CustomerSubclass: Retail or WholesaleInstance: John Smith

Retail and Wholesale customers automatically inherit customer address since it is part of the Customer class

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OOP: Object-Oriented Programming

Languages• C++

Can write both structured and object-oriented code

• Visual BasicRudimentary features of object-oriented language

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Third Generation Languages

Java• Cross-platform• Java Virtual Machine (JVM)

– Sits on top of computer’s regular platform– Translates compiled Java code into

instructions for the specific platform

• Applets

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