Slide 03 - Introduction to C

8/10/2019 Slide 03 - Introduction to C

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Computer Science Department FTSM

Introduction to C

Knowledge:

Understand the complete structure of C programs in Linuxenvironment

Skill:Edit, compile and execute C programs


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TK1913-C Programming 2

Introduction /* Task: This program calculates BMI */#include #define WEIGHT 60.0#define HEIGHT 1.53

void main(void) {float bmi;

bmi = WEIGHT / (HEIGHT * HEIGHT);

if (bmi > 25.0)printf( \nYour BMI is %.2f. Need to lose weight! \ n, bmi);

}

Resembles AlgebraicExpression

Augmented by certainEnglish keywords

eg. if , else, while

C is a High-level LanguageCan also be used at lower-level

This flexibility allows it to beused for SYSTEMPROGRAMMING (eg.Operating systems likeUNIX and WINDOWS)

APPLICATIONPROGRAMMING

(Billing System,Sistem Semut ? )

C has small instruction set,though the actualimplementations include

extensive li brary functions

myfunction.h

C encourages usersto write additional

library

functions of their own

Finally, C programs are highlyportable.

They can be executed on differentplatforms without having to be

recompiled (or with little modification)


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Editing C Program in Linux Use vi editor

$vi program_name.c

Use pico editor $pico program_name.c

Use emacs editor

$emacs program_name.c

Example: $pico myprogram.c

This is only an example ofprogram name. You can give

any name that you like.


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Compiling C Program in Linux To compile C GNU: $gcc program_name.c

An error message will be displayed if there isany syntax error Needs to be rectified until

there is no more errorsIf succeeded, the output will be generated intothe execution file, namely a.out

To display the output on the screen: $a.out

Example: $gcc myprogram.c$a.out


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Another method to compile C GNU:$gcc o file_name program_name.c

An error message will be displayed if there is anysyntax error Needs to be rectified until there isno more errors

If succeeded, the output will be generated intothe execution file, namely file_name

To display the output on the screen: $file_name

Compiling C Program in Linux

Example: $gcc output myprogram.c$output

This is only an example ofexecution file name. You can give

any name that you like.


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Don t WorryBe Happy Got confused?? Dont

worry, youll acquire thisskill during the labsession. Ensure you know

your lab group andschedulegood luck!


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History of C LanguageC was originated from 2 programming languages, namelyBCPL and B BCPL was developed by Martin Richards in year 1967. It

was intended as a language to develop operating systemsand compilersB was developed by Ken Thompson in year 1970s. It wasused to develop UNIX operating system at Bell

LaboratoriesC was developed by Dennis Ritchie in year 1972. Itreplaced B as the language to develop UNIX operatingsystem at Bell Laboratories


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C Program StructurePreprocessorInstruction

void main (void){

}

Statement

Global Declaration

Local Declaration


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Example of C Program

#include

void main(void) {

printf(Welcome to UKM!);

}

program

Main function

statementPreprocessor instruction


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Preprocess Instruction2 types of preprocess instruction that arenormally used:

#include

#define

#include is used to include certain files into the program. Those files need to be included

because they contain the necessary informationfor compilation (e.g. stdio.h file containsinformation about printf function)


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Preprocess Instruction#define is used to declare macro constants

Example:

#include #define PI 3.141593

void main(void) {

float luas;luas = PI * 7 * 7;printf(Luas %.2f:, luas);

}

Macro constant

Before preprocessExample:#include #define PI 3.141593

void main(void) {float luas;luas = 3.141593 * 7 * 7;printf(Luas %.2f:, luas);

}

After preprocess


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Main Function

Every C program must have a mainfunction, called main()

The execution of C program starts frommain() function


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StatementSentence -like action steps that are written in the

body of the functionIn C, all statements must be ended with ; symbol

Example: A statement to display a string ofcharacters on the screen by using printf() function

printf(Welcome to UKM);

Output:

Welcome to UKM


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CommentYou could include comments in your program to easeunderstanding

Comments will be ignored during compilation

A block of comment is labeled with /* (start) and */ (end) compiler will ignore any text written after /* symbol till */ symbol is found

Nested comments (comment within comment) are notallowed, for example:

/* my comment /* subcomment */ my comment continues */


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Example of C Program

Welcome to

Fakulti Teknologi dan Sains Maklumat

What will the output be?


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Slide 03 - Introduction to C