Understand Programming Languages

7/31/2019 Understand Programming Languages

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Program: A set of step-by-step instructions that directs a

computer to perform a specific task and to producethe required results.

Programming: Programming is a process of designing/ creating a

program.

Programmer: Programmer is a person who writes the program.


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A set of rules and reserved words (keywords) that

can be used to tell a computer what are theoperations to be done.

Artificial language composed by a fixed vocabularyand set of rules is used to create instructions for thecomputer to follow.

Now, there are over 200 programming languages inthe world. For example: Cobol, Pascal, C, C++, andFortran.


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Example: People communicate using human languages, such asBahasa Melayu, English and Japanese.

Interaction

HUMAN LANGUAGE (BAHASA MELAYU)

People communicate with computers using programming languagessuch as C, C++ and Cobol.

PROGRAMMING LANGUAGE (C, C++, COBOL)

Interaction


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#include

#include

main()

{

int a,b,c; /* hold variables value*/

int sum; /* variable to hold total (a+b+c) */

float avg; /* variable output*/

clrscr();

printf (Input three numbers:); /* ask user to enter 3 numbers */

scanf (%d %d %d, &a, &b, &c);

sum = a+b+c; /* calculate total of a, b and c*/

avg = sum / 3; /* calculate average*/

printf (Average of the numbers: %.2f, avg); /* Display the average */

}


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Executable program: program that can operate acomputer

Executable programs are written with binarynumbers, which is a computers internal language

(machine language) An example of a simple machine language program

containing two instructions is:11000000000000000001000000000010

11110000000000000010000000000011

Opcode is short for operation code; tells thecomputer the operation to be performed.


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Assembly language: uses the substitution of word-

like symbols for the opcodes, and decimal numbers

and labels for memory addressesLOAD first

ADD second

MUL factor

STORE answer


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Machine and assembly languages are low-level languages becausethey both use instructions that are directly tied to one type ofcomputer.

Programs written in a computer language are referred to as source

programs and source code.

When each statement in a high-level source program is translatedindividually and executed immediately upon translation, theprogramming language is called an interpreted language.

Interpreter: program that translates each statement in a high-levelsource program and executes it immediately upon translation.


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Compiled language: the statements in a high-levelsource program are translated as a complete unitbefore any individual statement is executed.

Compiler: translates a high-level source program as acomplete unit before any statement is executed The output produced by the compiler is called an

object program (machine language version of thesource code).

Linker: combines additional machine language codewith the object program to create a final executableprogram


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A fourth-generation programming language(or 4GL) is a programming language designedwith a specific purpose in mind such as thedevelopment of commercial business

software


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A translator is a program that:

Checks syntax of a program to ensure theprogramming language is used correctly, by givingyou the syntax-error messages, which is known asdiagnostics.

Translates a program into language that thecomputer can understand.

Produces descriptive error messages known assyntax-error to programmer if there are errors inthe programs.


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Syntax set of rules to be followedwhen writing a program, these rules

are similar to the grammatical rules

in English.

Example:

Message displayed on the screen is

please enter a number.

C Language:

printf(please enter a number);

Syntax Error

error in the use of aprogramming language.

Example in C:

Statement: clrscr()

If semicolon (;) is not placed after

statement, a message will display:Error DIT103.CPP: Declaration

syntax- error

The correct syntax is:

clrscr();


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Translates the whole program at one time.

Also called assembler program.

A program, which is used to convert assembly language tomachine language.

sseg segment stackdb 256 dup (?)

sseg ends

dseg segmentdata db 2 x 4 = dseg endscseg segment

assume cs:cseg:ds:sdeg:ss:sseg.es:nothingStart

Assembler

Assembly Language Machine Language

11101 100000100000

111101011100011101000111111001011100010001110 11011000

1011100010001110 11000000

proc far


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Translate the whole program at one time.

Translates the source code, for example COBOL language

to machine language. Used to translate C, COBOL and other language.

# include

main( )

{

int x, y, z, sum;double avg;

printf(" Enter 3 numbers:");scanf("%d %d %d",&x, &y, &z);

sum = x + y + z;

avg = sum / 3;

printf("x = %d y = %d z = %d ",

x, y, z);

printf("the average is = %f",avg);

return 0;}

11101 100000

100000

1111010111000

11101000

11111100

10111000

10001110 11011000

10111000

10001110 11000000

Compiler

C Language

Machine Langeage


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Program that translates a high level language to machine

language.

It translates one line at a time and executes each line afterit is translated.

Displays feedback as the error occurred.

Used to translate BASIC and SQL language.

10001110 11000000

10111010

10111011

10001101 110110

10111111

10110000 000000010

10110011 000001000

11100011 111111000

00001110 110000

1010000010111001

10100100

Interperter

Basic Language Machine Language

BASIC PROGRAMAVERAGING THREE

INTEGERS

PRINT Mengira Purata

PRINT ---------------------

PRINT Nilai A = ; 20

PRINT Nilai B = ; 30

PRINT Nilai C = ; 40

PRINT Purata tiga nombor ialah; (20+30+40)/3

END


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Program that fulfils all the specifications, requirements and

objectives.

For example: ATM machine. When a user withdraws RM200,the user will get RM200 in cash.

To ensure accuracy, programmer needs to define a controlto prevent invalid value.

No errors. Produces output as required. Information is reliable if the user can depends on its

accuracy and completeness.

Example: the balance in Touch N Go card.


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Easy to use and learn. Programmer or non-programmer can

use the interaction.

Example, LRT-STAR machine (ticket) can be used byanyone.

A program that is easily understood, tested and modified

without having to change the whole program. The program

may be changed by any programmers at anytime to fulfilthe current requirement.

Example: Total digit of telephone number can be changedfrom 7 to 8 digits without changing the existing applicationprogram.


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Fast program execution and quick access to data to

generate output.

Example: Tickets System in LRT-STAR System.

A readability program is:

A clear and understandable program.

Using meaningful name for variables.

Have explanations on the programs function.

Instruction is written by using spacing in between words.

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Understand Programming Languages