Chapter 3 - Introduction to C

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ENG 054: COMPUTING

ENGINEERING II

Chapter 3 :

Introduction to CProgramming


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Objectives :

1. To understand the basic components of C

program

2. To introduce the concepts of

- Data types

- Identifiers : variables & constants

- Arithmetic operators3. To introduce standard input & output function

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Components of C Program

C program have parts and components thatserve specific purposes

BUT, the parts of C programs are not always inthe same place

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Example of C Program

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Output of C program

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output



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Example :Write a program to calculate and display an areaof a cylinder side.

Area of cylinder side is calculated using the

following formula :-

Area of cylinder = 2rh ; where

r is the radius and h is the height.

Your program will calculate the area of cylinderside based on the given input (i.e radius andheight) from the user.

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Structure of a C Program

main() function

//Written by: Rosmiza Wahida/*This program is to calculate the area

of a cylinder*/

#define pi 3.142

float A_cyl;

int main()

{

float radius, height;

printf(Please enter radius: );

scanf(%f,&radius);

printf(Please enter height: );

scanf(%f,&height);

A_cyl = 2*pi*radius*height;

printf(Area for the cylinder is

%f , A_cyl);

return 0;

}

Preprocessor directive

Global declaration

Local declaration

Statements

#include

Comments

ReturnStatement

Function body



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Will be read first before the program is compiled

Indicated bypound sign (#) together with keyword

#include to include the contents of another file

#define to define global variable/constant

** No space between # and include

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Preprocessor Directive



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#include

stdio.h

Is the name of the file that is to be included.

Dot h indicates the type of the file header file

Allow C program to display output on the screen printf() and read input from the keyboard scanf()

#define pi 3.142 pi - Name of constant

3.142 value of the constant

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Preprocessor Directive



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main() function

C Program can have one or more functions, exactly oneMUST be main() function

int main()

int stands for Integer. It indicates that the function

sends an integer back to operating system when it is finishedexecuting

main() the name of the function

MUST be followed by set of braces ({ }) indicates a

block, the beginning and ending of a function

All statements (function body) that make up a function areenclosed in a set of braces

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Comments

Use : to document programs and improveprogram readability

Help other people read and understand othersprogram

IGNORED by C compiler and DO NOT causeany machine-language object code to begenerated.

DO NOT cause the computer to perform anyaction when the program is run.

CAN be put ANYWHERE in the program

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Comments

Two format Line comment

Marked by two slashes (//) at the beginning of comment

For short comment in a single line

Example://Written by : Rosmiza Wahida

Block comment Marked by opening token(/*) and closing token (*/)

For long comment

Example :/*This program is to calculate the area of a cylinder*/

Comments CANNOT be nested (comments insidecomments)

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Function Body

Enclosed by a set of braces ({ }) Function contains

Local declaration

Declaration of data that will be used for the function/program

Example :float radius, height;

Statements @ Program body

Set of instructions of what the function/program should do

Return Statement

Return value that sends back to operating system Example :

return 0;

** 0 usually indicates that a program executes successfully

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Common Programming Language

Elements Syntax

Rules that must be followed when constructing a

program Lines

A line is a single line appear in the body ofprogram

Statement A complete instruction that causes the computer

to perform some action

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Common Programming Language

Elements Keywords (Reserve Words)

Words that have special meaning and used forintended purpose

Programmer-Defined Identifier (Identifier) Words/names defined by programmer. Symbolic

names refer to variables or functions

Operators

Operator perform operations on one or more operands Punctuations

Punctuation characters mark the beginning or endingof a statement, or separate item in a list

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Punctuations

Comma (,) use to separate item in a list Use to separate item in a list

Example :

float radius, height;

Semicolon (;)

Use at the end of a complete instruction

Example :

float radius, height;printf(Please enter radius: );

A_cyl = 2*pi*radius*height;

return 0;

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Reserve Word/Keyword

Special words reserve for C Program which havespecific meaning and purpose

CANNOT be used as identifiers or variable name

Appear in lower case

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C and C++ Reserved Words

autobreakcase

charconst

continuedefault

dodoubleelse

enumexternfloatfor

gotoifint

longregisterreturnshort

signedsizeofstaticstructswitchtypedef

unionunsigned

voidvolatilewhile

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Identifiers

Allows programmers to NAME data and otherobjects in the program

variable, constant, function etc.

Rules in naming identifiers

MUST consist ONLY of alphabetic characters(uppercase or lower case), digits and underscores (_)

First character MUST be alphabetic character orunderscore

CANNOT contain spaces CANNOT duplicate with any reserved word

** C is CASE-SENSETIVE

this means that NUM1, Num1, num1, and NuM1 are

four completely different name.

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Example of Valid & Invalid

IdentifiersValid Identifiers Invalid Identifiers

A

student_name

_aSystemName

Pi

Al

stdntNm

anthrSysNm

PI

$sum // $ is illegal

2names // cant startwith 2

stdnt Nmbr // cant havespace

int // reserved word

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Variables

Variable names correspond to locations in thecomputer's memory

Every variable has a NAME, a DATA TYPE, a SIZE

and a VALUE A variable is created via a declaration where itsname and type are specified.

Example :

int integer1, integer2, sum; Whenever a new value is placed into a variable

(through scanf(), for example), it replaces (anddestroys) the previous value

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Variable Declaration

Specifies in the memory to reserve a specific space forthe variable that have the specific location and can storespecific data type.

MUST be declared before the executable of the statement

Variable need to FIRST declare before it being used Syntax :

data type variable name;

Example

int maxItems = 0;float payRate;

double tax;

char code;

int a, b; // equivalent to int a; int b;

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Example of Variable in Memory

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long int

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Data Types

Variables are classified according to their data type Determine the kind of information stored in variables

Address, phone numbers, price, distance, and etc.

Functions also have types which determine by the data it

returns C Program have 5 standard data types:-

void

int

Integer e.g. 1244,-87

char

Character e.g a, A

double

Floating-point e.g 0.5678, -3.25

float : Floating-point (less precision)

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Data Type - void

Has no values and operations

Usually use for function

Example :

void printMessage()

Both set of values are empty

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Data Type - char

Use for storing character Stored in memory as 1-byte integer data type

WHY? Each printable and non-printable character isrepresented by a unique number in computer memory.

Observe the output!!

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Numeric Data Type

In C Program, numeric data types are brokeninto 2 categories:-

Integer

Whole numbers Example : 12, 157, -34 and 2

Floating point

Numbers that have decimal point

Example : 23.7, 189.0231 and 0.987

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Numeric Data Type

Both Integer and Floating-point data type can bebroken into more classifications

Primary consideration for selecting data type:-

The largest and smallest number that maybe

stored in the variable How much memory does the variable use

Whether the variable stores signed or unsignednumbers

The number of decimal places of precision thevariable has

The size of variable is the number of bytes of

memory it uses. (> varible

> range can hold)

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Integer Data Type

To store WHOLE NUMBER without fraction

C program supports 3 different sizes of integer

short int

int

long int

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Type Byte Size Minimum

Value

Maximum Value

short int 2 -32,768 32,767

unsigned short int 2 0 65,535

int 2 -32,768 32,767

unsigned int 2 0 65,535

long int 4 -2,147,483,648 2,147,483,647

unsigned long int 4 0 4,294,967,295

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Floating Point Data Type

To store FLOATING-POINT number

C program supports 3 different sizes of integer

float

double

long double

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Type Byte

Size

Precision Range

float 4 6 10-37 ..1038

double 8 15 10-307 ..10308

long double 16 19 10-4931 ..104932

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Variable Initialization

To establish the first value that the variable willcontain

Syntax :

data_type variable_name = value; Example :

int count = 5;

int sum = 0;

int count=0 , sum = 0;

char letter = B;

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Constants

To define values that CANNOT be changedduring the execution of a program

Types of constant Integer constant

Float constant

Character constant

String constant Symbolic constant

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Constants

3 ways of defining a constant Literal Constant

Defined Constant using preprocessor

Defined Constant using const

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Literal Constants

An unnamed constant used to specify data If the data cannot be changed, it can simply code

the value itself in a statement

Example :

A // a char literal

5 // a numeric literal 5

a + 5 // numeric literal

3.1435 // a float literal Hello // a string literal

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Defined Constants

2 ways :- Using preprocessor : #define

Example :

#define pi 3.142

Using keyword : const Example

const int a = 1;

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Assignment Operator (=) To assign the value of variable or expression into

to a variable.

Example:

a = b;

result = n1*n1;areaOfCircle = 3.142 * r * r;

alphabet = A;

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Arithmetic Operators

Use to manipulate numeric values and performarithmetic operation

Assume ;

int a=4, b= 5, d;C

Operation

Arithmetic

Operator

C

Expression

Value of d after

assignment

Addition + d = a + b 9

Substraction - d = b - 2 3

Multiplication * d = a * b 20

Division / d = a/2 2

Modulus % d = b%3 2

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Arithmetic Operators Assignment

OperatorsAssume ;

int x = 4, y=5, z=8;

AssignmentOperator

SampleExpression

SimilarExpression

Value of variableafter assignment

+= x += 5 x = x + 5 x=9

-= y -= x y = y - x y=1

*= x *= z x = x*z x=32

/= z /=2 z = z/2 z = 4

%= y %=x y = y%x y=1

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Arithmetic Operator Increment &

Decrement OperatorOperator Called Sample

Expression

Similar

Expression

Explanation

++ preincrement ++a a = a +1

a += 1

Increment a by 1, then use

the new value of a in

expression in which a reside

++ postincrement a++ a = a +1

a += 1

Use the current value of a in

the expression which a

reside, then increment a by 1

- - predecrement - - a a = a -1

a -= 1

Decrement a by 1, then usethe new value of a in

expression in which a reside

- - postdecrement a - - a = a -1

a -= 1

Use the current value of a in

the expression which a

reside, then decrement a by

1

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Example : Increment Operator

Statements Outputint c=5;printf( "%d", ++c );

c=5;printf( "%d", c++ );

int c=5;++c;printf( "%d", c );

int c=5;c++;

printf( "%d", c );

char alphabet = 'D';alphabet++;printf ("\n%c", alphabet);printf ("\n%c", alphabet++);

printf ("\n%c", ++alphabet);

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Decision Making : Relational &

Equality Operator Assume ;

int y=6, x=5;

Relational Operators Sample Expression Value

> y > x T (1)

= x > = 3 T (1)

< = y < = x F (0)

Equality Operators Sample Expression Value

= = x = = 5 T(1)

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Logical Operator

Logical Operators Called Sample Operation

&& AND expression1 && expression 2

| | OR expression1 | | expression2

! NOT ! expression

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Example : Assume;

int x=50;

SampleExpression

Expression !Expression

!(x==60) 0 (False) 1 (True)

!(x!=60) 1 (True) 0 (False)

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Example : AND (&&)

Assume; int x=4, y = 5, z=8;

Sample ExpressionExpression1 Expression2 Expression1

&&

Expression2

( y > 10) && ( z < =x ) 0 (False) 0 (False) 0 (False)

( z < = y) && ( x = = 4) 0 (False) 1 (True) 0 (False)

( y ! = z) && ( z < x ) 1 (True) 0 (False) 0 (False)

( z > = y ) && ( x ! = 3) 1 (True) 1 (True) 1 (True)

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Example : OR (||)

Assume;int x = 4, y=5, z=8;

Sample ExpressionExpression1 Expression2 Expression1

&&

Expression2

( y > 10) || ( z < =x ) 0 (False) 0 (False) 0 (False)

( z < = y) || ( x = = 4) 0 (False) 1 (True) 1 (True)

( y ! = z) || ( z < x ) 1 (True) 0 (False) 1 (True)

( z > = y ) || ( x ! = 3) 1 (True) 1 (True) 1 (True)

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Operator Precedence

Operators Associative

( ) Left to right

++ - - + - ! Right to left

* / % Left to right

+ - Left to right

< >= Left to right

= = != Left to right

&& Left to right

| | Left to right

= *= += - = /= %= Right to left

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Example : Operator PrecedenceExample 2

int a=15, b=6, c=5, d=4;

d *= ++ba/3 + c

1. d *= ++ba/3+ c

2. d*=7- a/3+c

3. d*=7- 5+c

4. d*=2 + c

5. d*= 7

6. d = d*7

7. -160

Example 1

int a=10, b=20, c=15, d=8;a*b/(-c*31%13)*d

1. a*b/(-15*31%13)*d

2. a*b/(-15*31%13)*d

3. a*b/(-465%13)*d

4. a*b/(-10)*d

5. 200/(-10)*d

6. -200*d

7. d = 28

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Standard Output & Input Function

Output function printf() To display information on the computers screen

Example :

printf(Programming is great FUN!! Loving IT!);

Input function scanf()

To read data typed from the keyboard

Example :

printf(Please enter an integer value >>\n);

scanf(%d, val1);

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Escape Sequence

Indicates thatprintf() should do something outof the ordinary

When encountering a backslash(\) in a string,the compiler looks ahead at the next characterand combines it with the backslash to form anescape sequence.

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Standard Output Function

2 Syntax ofprintf()

printf(FormatControlString);

Example : printf (Hello Dear, \n);

printf(FormatControlString Format specifier,PrintList);

Example : int year=2006;

printf(Year is %d, year);

Specifier for printing an

integer value

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Common Output Format Specifiers

Specifies the argument type

Data Type Format Specifiers

int %d

float %f

double %lfchar %c

string %s

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Example :printf() function

printf( "Sum is %d\n", sum );

%d means decimal integer will be printed sum specifies what integer will be printed

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Different Ways of Formattingprintf()

Display normal messageprintf("Hello Welcome to C");

Display spaceprintf("\tWelcome");

Display new lineprintf("\n");

Printing value of variableprintf("Addition of two Numbers : %d",sum);

Printing value of the calculationprintf("Addition of two Numbers : %d", num1+num2);

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Multiple format specifier

printf("I Love %c %s",'c',"Programming");

Display integer in different styles

printf(\n%d",1234);printf(\n%3d",1234);

printf(\n%6d",1234);

printf(\n%-6d",1234);

printf(\n%06d",1234);

Output1234

1234

##1234

1234##

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Display fraction number in different stylesprintf("\n%f",1234.12345);

printf("\n%.4f",1234.12345);

printf("\n%3.2f",1234.12345);

printf("\n%-15.2f",1234.12345);printf("\n%15.2f",1234.12345);

Output

1234.123450 //by default, it will print 6 values after the decimal

1234.1235

1234.121234.12########

########1234.12

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Display fraction number in different styleschar str[]="Programming"; // Length = 11printf("\n%s",str); // Display Complete Stringprintf("\n%10s",str); // 10 < string Length, thus display Complete

Stringprintf("\n%15s",str); // Display Complete String with RIGHT

alignment

printf("\n%-15s",str); // Display Complete String with LEFTalignment

printf("\n%15.5s",str); //Width=15 and show only first 5 characterswith RIGHT alignment

printf("\n%-15.5s",str); //Width=15 and show only first 5 characterswith LEFT alignment

OutputProgrammingProgramming####ProgrammingProgramming##############ProgrProgr########## J uliana J aafar

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Standard Input Function

Syntax ofscanf() scanf(FormatControlString, InputList);

Example: int age;scanf(%d, &age);

** FormatControlString MUST consist of formatspecifiers only

** Each element in InputList must be an ADDRESS to a

memory location for which it must be made into** Address of memory location is specified by prefixing

the variable name with an ampersand character (&)address operator

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Common scanf() Format Specifiers

Data Type Format Specifiers

int %d

float %f

double %lf

char %c

string %s

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Example : scanf() Function

scanf( "%d", &integer1 );

%d - indicates data should be an integer value

&integer1 - location in memory to store variable

** When executing the program the user respondsto the scanf() statement by typing in a number,

then pressing the enter (return) key

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Example : scanf() Functiondouble height;

int year;

scanf(%lf, &height);

scanf(%d, &year);

scanf(%lf, height); /* This is an error!! */

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Example : Inputting Multiple

Values with a single scanf()int height;

char ch;

double weight;

scanf(%d %c %lf, &height, &ch , &weight);

Put space between the specifiers

** It is always better to use multiple scanf()s, whereeach reads a single value

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611 /* Fig. 2.5: fig02_05.c

2 Addition program */


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1. Initializevariables

2. Input

2.1 Sum

3. Print

Program Output

2 Addition program /3 #include 45 int main()6 {7 int integer1, integer2, sum; /*declaration */89 printf( "Enter first integer\n" ); /*prompt */10 scanf( "%d", &integer1 ); /* readan integer */11 printf( "Enter second integer\n" ); /*

prompt */12 scanf( "%d", &integer2 ); /* readan integer */13 sum = integer1 + integer2; /*assignment of sum */14 printf( "Sum is %d\n", sum ); /*print sum */1516 return 0; /* indicate that program endedsuccessfully */17}

Enter first integer45Enter second integer72

Sum is 117

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ExampleofC Program

#include

int main()

{

int num1;

scanf(%d,&num1 );

printf(You key in %d\n,num1);

return 0;

}

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Structure of a C Program

Chapter 3 - Introduction to C

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Transcript of Chapter 3 - Introduction to C