Getting Started With Coding

By:

Mr. Baha Hanene

Chapter 3

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Learning OutcomesWe will cover the learning outcome 02 in this chapter i.e.

Use basic data-types and input / output in C programs. (L02)

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ContentsIntroduction to ProgrammingStages & Steps of Writing ProgramsPreprocessor DirectivesMain FunctionOutput StatementVariables in CAssignment StatementsSample ProgramsReferences

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Programming IntroductionA language which is used to instruct

computer to perform different tasks according to the requirements.

Every programming language has following basic things.

Declarations Assignments Control Statements I/O (Input/output)

Statements

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Programming IntroductionAny programming language consists of its

own keywords and syntax rules that distinguishes it from other programming languages.

If you want to program in a specific language, you need the compiler of this specific language.

For example, C language compiler translates programs written in C language to machine language.

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Programming StyleKeep it clear & simpleKeep it shortThink it through in advance

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Stages & Steps of Writing ProgramsSpecificatio

nDesign

Coding

Testing

Documentation

Maintenance

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Preprocessor DirectivesIn C programming whenever you see lines

that begin with a in column 1 are called preprocessor directives (commands)

The #include<stdio.h> directive allows the processor to include basic Input / Output in the program at this point.

#

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stdio.hThis header file we include in all programs

where we need to use basic I/O commands e.g.

printf(“”); scanf(“”);Some functions are very difficult and very

long to write, these header files contains built in functions to provide us help in writing the programs.

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void main( )Every C program has a main function, this is

where the program starts it’s execution, as this is the first function to execute in the whole c program.

The reserved word “void” shows that this function will not return any value.

Each C program can contain only one main function e.g.void main()

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Function BodyA left brace (curly bracket) -- { -- begins the

body of every function. A corresponding right brace -- } -- ends the function body.

void main(){

…………

}BO

DY

Main Function

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printf(“”);This line is called a C statementprintf(“”); is a function which is used to instruct

computer to display something on computer screenAll text, special symbols you will type inside

printf(“”); between the double quotations i.e. “……..” will be displayed as it is on your computer screens except few commands like /t, /n, %i etc.e.g.

printf(“Welcome at KIC”);

Notice that the above line ends with a Semicolon ; (every C statement ends with a semicolon i.e. ;)

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Sample Program Explanation#include<stdio.h>

void main()

{

printf(“Hello to programming”);printf(“\n Welcome at KIC”);printf(“\t at Fall 2010/11”);

}

Header File used for Input / Output

Main Function Necessary to start any C program

Output Statement used to display on screen

Function Start

Function End

\t\n Start New

Line

Give Space between text

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Variables in CIn computer programming, a variable is a

name given to some known or unknown quantity or value, for the purpose of allowing the name to be used independently of the value it represents

[Data Type] [Variable Name] ;Data Types: In C programming there are more data types but we generally use the following data types. (more details in next chapter)

1. int2. float 3. char

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Variables in CVariable Name: You can give any name to the

variables in c but there are few rules for writing variable names. (A-Z) The first character must be a letter Space is not allowed between names of identifiers (&*^%$#@) Special symbols are not allowed in

identifier names - Hyphens are not allowed in identifier names

however underscores _ can be used (int, float, private etc.) The reserve words are not

allowed in identifier names.

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Variables in CSome valid identifiers / variable nameshello j9 box22a get_data bin3d4

countSome reserve words (can’t be used as

identifier):private else static int const float

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Variables in Cvelocityfredatime-of-day inttax_ratex24xfirst value radio@4emp.

velocityfredatime_of_day INVALIDtax_ratex2x4first_value radio4emp

RIGHTRIGHTRIGHT

RIGHTRIGHTWRONG

WRONGWRONGWRONG

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Variables in CHow & where we write variables in C

programming….?We usually declare all variables inside main

function for example:

#include<stdio.h>

void main(){ int avar ; int salary ; float percentage ;}

Data Type Variable Name

Semi Colon (every C statement ends with a semicolon ;)

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Sample Program Multiple Variable Declaration

Any Questions

????

?????

Assignment

Statements

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Assignment StatementsBefore using variables in assignment statements you

should define / declare them first e.g. int a;Assignment Statements

first_number = 35; second_number = 21; sum = first_number + second_number;

The first two statements assigns the values 35 and 21 to the variables first_number and second_number respecitively

The next statement assigns the sum of the two values to the variable sum.

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Sample Program Header File

Main Function

Function Body

Variable Declaration

Assignment Statements

Screen Output

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Displaying Variable ValueDo you see something different in normal

printf statements and these which we have seen in the last sample program???

What are these

things????

%d These are called Format Specifiers used to display the value stored in the variable i.e. Inside computer memory

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Sample Program Output

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The Logical FlowSource Program

CompileSyntax Error

OK

Object Code/ Program

Run Run-time Error

OK

ResultLogical Error

OK

ENDContinue

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Referenceshttp://en.wikipedia.org