computer programming (tmk 3102) lecture notes 5

8/9/2019 COMPUTER PROGRAMMING (TMK 3102) LECTURE NOTES 5

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TMK 3102-Chap 5: Variables &

Constant

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Chapt er 5: Var iables andConstants

Session Plan (Week 5):To understand:the concept of storage location representationas identifiers


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TMK 3102-Chap 5: Variables &Constant

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Ident i f ie r An identifier is a sequence of characters that

consist of letters, digits, underscores (_), anddollar signs ($).

An identifier must start with a letter, anunderscore (_), or a dollar sign ($). It cannotstart with a digit. An identifier cannot be a reserved word.

An identifier cannot be true, false, ornull. An identifier can be of any length


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J ava Keyw ords

do new abstract break synchronized

if default assert private implements

int goto this throw protected

try return import public instanceof

byte else throws double transient

case void boolean short package

for final interface static extendschar long finally strictfp volatile

class float native super while

const catch continue switch


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Ident i f ie rs

Identifiers are:

Variable Constant

others


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Var iab le

A name associated with a memory cell whosevalue can change

Needs to be declared:variable_type variable_name;

Example:int x;int entry_time, charge;


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Type of Var iab le

Logical Type

1. Boolean

Textual Type

2. char

Integral Type

3. byte

4. short

5. int

6. long

Floating Type

7. float

8. double

8 Primitives DataType Under 4

groups


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Logic a l Type (boolean)

boolean data type has 2 literals

true and false

example of declarations

boolean status;

Declared a variable status as a

boolean type.status = true;

assign a value of true to variable status


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Tex t ua l Type (c har )

Represents 16 bits unicode character

(0,65536)

Declarationchar em ;

Declared a variable em as char type

Must has its literals enclosed in single

quotes ( )

em = m

Assigning value m to variable em


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Can be in form of :

Escape Character

char thiIsTab;

thisIsTab=/t;

Specific Unicode character

char phi ;

phi=\u03A6; //for symbol


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How do we presenting words or sentences?

use String data type.

it is not part of primitive data type. It

is a class.


String greeting;

Declared a variable greeting as a string type.

String attention, oneChar;//another


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Has its literals enclosed in double

quotes ( )

Example

greeting = Good Morning;

attention = achtung!!!!;

oneChar = a;


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In t egra l Type

byte 8 bit (-128,127)

short 16 bit (-32768,32767)

int 32 bit (-2147483648,2147483647)

long 64 bit (-922337203684547758808

,92233720368454775880


int markah;

declared a variable markah

markah = 76;

assign a value 76 to it.


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In t egra l Type (byt e , shor t , in t ,long)

Has 3 forms: Decimal, Octal and

Hexadecimal

int jumlah;jumlah = 77; //decimal

jumlah = 080;//octal

//leading 0 indicate octal value

jumlah = 0xBAAC; //hexa

//leading 0x indicates hexadecimal value


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Float ingType

float 32 bit (1.4e-045,3.4e+038) precision = 6,7

double 64 bit (4.9e-324,1.8e+308) precision=15


float CGPA;

double diameter;


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Var iab le

Variable Declaration:

Example 2:

float matric;

matric is a ??? variable


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Self Chec k (THINK !!!)

What is the type of the values 0 and0?

Determine the legalities of the followingidentifiers?

Define a variable to hold your age.

Greeting1

g

void

101dalmatians

Hello, World


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Var iab le

Example:

Calculate and display the price of a number of apples if

the quantity in kg and price per kg are given.

Input: quantity and price_per_kg

Output: price

Process: price = quantity * price_per_kg


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Var iab le

Example:

int quantity;

float price_per_kg;

float price;

Why do wedeclare it as int?

Why do we

declare them as

float?


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Variable - Va lue Assignm ent

Example:

int number1, number2;

number1 = 25;

number2 = 23;

number1 = number2;

number1 ?

number2 ?

2523

23


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Example:

int quantity;

float price_per_kg, price;

quantity = 2;

price_per_kg = 4.50;price = quantity * price_per_kg;


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Example:

int quantity;

float price_per_kg, price;

quantity = 2;

price_per_kg = 4.50;price = quantity * price_per_kg;

quantity ?

price_per_kg ?

price ?

4.50

9.00

2


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Example:

int number1, number2;

number1 = 25;

number2 = 23;

number1 = number2;

How does this

program

segment work?


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Dec lar ing and In i t ia l izingin One St ep

int x = 1;

double d = 25.4;

char b = b;int number1 = x;

Is this statementcorrect???


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Constant

A variables whose values does not change.

How??

Put keyword final in front of the variable.

Do it in one step (declared and initialized)

final float PI = 3.14278;

final int dayOfJanuari = 31.


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Quest ions

What wrong with the Java statementbelow?

byte byteVar;

int intVar = 129;

byteVar = intVar;


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TMK 3102-Chap 5: Variables & 26

Thank You

computer programming (tmk 3102) lecture notes 5

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