Programming Chapter 1 Week 2

8/13/2019 Programming Chapter 1 Week 2

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FCS 0084 Programming Chapter 1

Introduction to C Week 2

Management and Science University 1

1.2VariablesandConstants

1.2 Variables and Constants

Two categories of data

Variable - the value can be changed during program execution

Constants - the value is fixed

DataData

Each variable has:1. Name

2. Type

3. Holds a valuethat you assign to them

VariablesVariables


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HINT:

Give your variable names that help describe the values they

are holding.

A studentname _counter firstName

a student_name SUKOM1998 secondName

x1 StudentName sukom_98 value1st

x2 SALARY Main value2nd

Valid Variable NamesValid Variable Names

main 2NDperson student name

printf employee name class code

int

question?

Invalid Variable Names: Why ?Invalid Variable Names

Note:

Uppercase andlowercase aredifferent.


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Note (*):C view a strings as a collection of characters.

We define string type based on char data type.

Example: char MyName[15];

Variable Types

Character

Integer

Floating-point number

String

char , unsigned char,signed char

int , unsigned int, signedint, long, short int,unsigned short int

float , double, long double * No strings type in C

Variable TypesVariable Types

Divided into four (4) main

subcategories:


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Data Range

Note:

Each

variable typehas it own

minimum

and

maximum

size the data

that its can

handle.

VariableType Minimum Maximum

char

unsigned char

signed char

int

unsigned int

signed int

short int

unsigned short int

signed short int

long int

signed long intfloat

double

long double

-128

0

-128

-32768

0

-32768-32768

0

-32768

-2147483648

-2147483648-3.4E+38

-1.7E+308

-1.7E+308

127

255

127

32767

65535

3276732767

65535

32767

2147483647

21474836473.4E+38

1.7E+308

1.7E+308


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Syntax:

DataType VariableName;

Two main categories:

Global Variables

Local Variables

#include

/*global declarations*/main( ){/*local declarations*/

clrscr();

printf();:

}

DeclarationVariable DeclarationsVariable Declarations

Referred asvari able scope


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/* Program to show variable declaration*/

#include

/* Global declaraion*/

intlength;floatbalance;

main(){/* Local declaration */

charfirstInitial;:

}

Two global

variables

One local

variables

Declare variable only if you

want to use it to handle the

data.

Each variable type require

different memory space. You can declare your

variables as local or global.

Global/Local Variable

Example of Variable DeclarationsExample of Variables Declarations


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/* Program to show variable declaration*/#include/* Global variable */

intlength;floatbalance;

main(){/* Global variable */

charFirstInitial;:}

Computer will allocate enough

spaceto handle the data from

that type.

length

balance

FirstInitial

2 bytes

4 bytes

1 byte

Memory Allocation

What happen to variable declaration ?What happen to variable declaration

RAM

Different compiler/computer may require differentsize of memory for each data type.


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Integer-1, 0, 1, 12, 15

Floating-point number

-1.5, 1.0, 3.14

Character

A, B, , 1, 2, , ?, *, $Strings

Management and Science University

Shah Alam

ConstantsConstantsConstants

I nteger constants

Floating-point

constants

Character constants

Str ing constants

?What does each of the followingmeans (constant or variable).

If constant, from what type ?

A A A


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ConstantsCharacter ConstantsCharacter Constants A character constantis a single character, enclosed in single quotation

marks.

Character constantshave integer valuesthat are determined by the

computers particular character set.

ASCII character set

ASCII:American Standard Code for Information Interchange

int code = 65;

printf(Code = %d, code);printf(Code = %c, code);

char code = Z;

printf(Code = %c, code);

printf(Code = %d, code);

Example:

Trace the output of both C codesbased on ASCII Character Set.


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Example:

Usingcombination

of ASCIIcharacters todraw a box.

/* DRAW A BOX */

printf(%c, 201); /* left top character */for(x=1;x


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Escape Sequence

Certain nonprinting characters, as well as the backslash (/) and the

apostrophe (), can be expressed in terms of escape sequences.

Character Escape ASCII

Sequence Value

bell (alert) \a 007

backspace \b 008

horizontal tab \t

009vertical tab \v 011

new line (line feed) \n 010

form feed \f 012

carriage return \r 013

quotation mark () \ 034

apostrophe() \ 039question mark (?) \? 063

backslash (\) \\ 092

null \0 000

Shown below are several

character constants,

expressed in terms of

escape sequences.

\n \t \b

\\ \ \

Note:

printf(\HELLO\);will printHELLOon screen.

printf("\007Attention, that was a beep!\n");


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A variable holds a value that you assign them using anassignment statement.

Syntax:

var iableName = Expression ;

Assigning Value to VariablesAssigning Values to Variables

main(){/* Local declaration */

intcount;

/* assign a value to a variable */count = 3;:

}

count

count3

RAM

Refer to 1.5


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Note:

String is a collection of characters to represents a Name (mother, father,

student, employee, car, building, shopping complex, software, ...), Address, etc

Two methods:

1. Array of characters

2. Character pointers

The base type is char.

C view a strings as a

collection of characters.

StringsHow to define strings data typeHow to define string data type

1.3CharacterArraysandStrings

1.3 Character Arrays and Strings

Array of characters

Syntax:

char VariableName[STRING_LENGTH];Note:

STRING_LENGTHisan integer constant.


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String VariableExample:char YourName[10];

String:Declared as an

array of character with

maximum length of

values 9 characters (One

space will be use by

NULL ZERO to indicate

the end of string).

Memory

Representation:

YourName[0]

YourName[1]

YourName[2]

YourName[3]

YourName[4]

YourName[5]

YourName[6]

YourName[7]

YourName[8]

YourName[9]

Each memoryslot represent acharacter


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Strings

representation

Example:

You will use the name without

number in bracket to input a

string value using scanf()or

gets() function:

/* prompt the user */printf(Enter your name :);

scanf(%s, YourName);

OR

gets(YourName);

IFthe input is Abdullah

MemoryRepresentation:

YourName[0]

YourName[1]

YourName[2]

YourName[3]

YourName[4]

YourName[5]

YourName[6]

YourName[7]

YourName[8]

YourName[9]

9 spaces are

required tohandle thestring

Abdullah

A

b

d

u

l

l

a

h

\0

Note: To print the string, you dont have to refer individual

characters. Print as a string:

printf(Your name: %s, YourName);


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H

E

L

L

O

\0

Example:

The string constant HELLO contains 6characters.

The length is 5.

When we put it as an argumentin printf()

printf( HELLO );

We will see

HELLO

displayed on screen.

In computer

memory

Null Zero

Used to indicate

end-of-string

String

length

Strings in memory

String constant as an argumentto printf() function

RAM


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1.4PreprocessorDirectives

1.4 Preprocessor Directives

There ate two main preprocessor directives:

#include - Include header file(s)

#define - Define symbolic constant(s) or macros

#include#include

Merges a disk file into your source program

Syntax:

#include

or

#include FileName


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Tell the processor to look the include file in adefault includedirectory ( c:\tc\include>); set up by your compiler.

Example: #include

include#include

Tell the processor first to look for the include file in the

directory where the source code is stored and, if missing,

the to look for it in the systems include directory.

Example: #include prototype.h

#include FileName

ASCII text file


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#define#define

It does nothing more than a search-and-replacecommand on aword processor.

Syntax:

#define argument1 argument2

#include

#define MAX 5/* symbo lic cons tan t defin it ion */:

printf(Max data is %d, MAX);Replaced with 5

define

Symbolic Constant

Example :

Defines a symbolic constant


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#defineTRUE 1

#defineFALSE 0

#defineNULL 0

#defineAND &&

#defineOR ||#defineNOTEQUAL !=

:

game_over = FALSE;

while( game_over NOTEQUAL TRUE) {

:

}

:

The definestatement is used to make programs more readable. Consider

the following examples,

In general, preprocessor constants are written in UPPERCASE.

The Program:

game_over != 1

The meaning:


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Macros

Macros are inline code which are substituted at compile time. The definitionof a macro, which accepts an argument when referenced,

#define SQUARE(x) (x)*(x)

y = SQUARE(v);

In this case, vis equated withxin the macro definition ofsquare, so the

variableyis assigned the square of v. The brackets in the macro definition

ofsquareare necessary for correct evaluation. The expansion of the macro

becomes

y = (v) * (v);

Defines a macro

The Program:


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Macros

Naturally, macro definitions can also contain other macro definitions,

#define AREA(x) (x)*(x)

#define RECTANGLE(x) AREA(x)

#define TRIANGLE(x) ((0.5)*AREA(x))

#define CUBE(x) (x)*(AREA(x))

The Program:


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Two method

Assignment statement

Input Functions

Input/Output

1.5InputandOutput

1.5 Input and Output

Assigning Value to VariableAssigning Value to Variable

Assignment StatementAssignment Statement

Syntax:

variableName = Expression;

Can be: another variable, constantor

combination of both.


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Example ofassignment statements:

Nett salary:

Area of a rectangle:

Volume of a cube:Area of a circle:

Linear graph:

Average of two numbers:

Sum of two numbers:

Current number of studentsis 30

Value of myAge is equals

to value ofyourAge

NettSalary =BasicSalary - (EPF+SOCSO);

AreaOfRectangle= 0.5 * length * width;

VolumeOfCube= length * width * depth;AreaOfCircle= 3.142 * pow(radius, 2);

y= (2 * x) + 3;

average= (first + second) / 2.0;

sum= value1st + value2nd;

currentStudent= 30;

myAge=yourAge;

Syntax: variableName = Expression;

FORMULA:


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#include

int v, w, x = 1; /* 2 global variables */

main()

{ float y=2.5, z; /* 2 local variables */

v = x;

w = v + 2;

z = 3.7;

printf(w = %d x = %d\n, w, x);

printf(y = %.2f z = %.2f\n, y, z);

}

Exampleof

program:

intv, w, x = 1; /* 2 global variables */

float y=2.5, z; /* 2 local variables */

v = x;

w = v + 2;

z = 3.7;

v

w

x

y

z

1

3

1

2.5

3.7

Assignment during

declaration

RAM


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Input FunctionsInput Functions

Use the scanf() function from stdio.h.Syntax:

scanf(CC, &Variable);CC: Conversion Characters

%c character

%s string%d integer%f float

&: The address of variable

No need for string type.

Example:/* input using scanf() */

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

scanf(%d, &c);

scanf(%f, &d);

/* variable declarations */

char a;char b[10];

int c;

float d;

Input Function


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#include

main(){ char fullName[35];

/* Label each of your input */

printf(Please enter your full name :);

scanf(%s, fullName);

printf(Your name is %s, fullName);

}

You can also simply use the gets();

gets(fullName);

Example:

Note:

Your maximum

length of name is

34 characters; not

35 characters.

Differentiate the use of scanf()and gets()to input string value.


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Output FunctionsOutput Functions Use the printf() function from stdio.h.

Syntax:

printf(CS, Variables);CS: Control String -Combination of string and

Conversion Character

/* variable declarations */

int age;

/* input */

printf(Please enter your age ? );

scanf(%d, &age);

/* output*/

printf(Your age is%dyears.,

age);

Example:

Output Function


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(A) Determine, as best you can, the purpose of each of the following C

programs. Identify all variables, input and output statements, assignment

statements, and any other special features that you recognize.

#include main()

{

printf(Welcome to the World of Computing !\n);}

#include #define MESSAGE \aWelcome to the World of Computing !\n

main()

{

printf(MESSAGE);}

Exercise


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#include

main()

{

float base, height, area;printf(Base :);

scanf(%f, &base);

printf(Height :);

scanf(%f, &height);

area = (base * height) / 2.;

printf(Area: %f, area);

}


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(B) Write a program that accepts your full name, address,height (meter),

weight (kilogram) and ages (years) from keyboards. Then redisplay all

accepted data onto computer screen using appropriate format.

HINTS:

Redisplay the data as registration form.

If the compiler complaint that your program has an error(s), read the

highlight statements at message windows to assist you correct the error.

(C) Find the library functionsthat gets the system date and time.

What header files that declare it.


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(D) Explain the purpose of each library functions listed below.

Named the header file that it belongs to.

Find or write a simple program to show how to use it.

strlen()

strcpy()

strcat()

strupr()

strlwr()

strcmp()

getch()

getche()

tolower()

toupper()

fopen()fclose()

fscanf()

fprintf()

sqrt()

pow()

atoi()

itoa()

gotoxy()

textcolor()

textbackground()

gettime()

getdate()random()


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Printf is also known as cout

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Programming Chapter 1 Week 2