topic 2 student copy

8/3/2019 Topic 2 Student Copy

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Prepared by: Saltihie Bin Zeni

Jabatan Kej. Elektrik, PMU3 2 1 Start


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OVERVIEW

2.1

Understand constant andvariables

2.2

2.3

Understand operator andexpression


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2.1 Understand constant and variable

Constant

Values that do not change during program execution. Example : conts double PI = 3.14159 // conts is a

reserved word

Variables Variables are like small blackboards

We can write a number on them

We can change the number We can erase the number

Example: int answer;


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Identifiers Identifiers

Variables names are called identifiers Choosing variable names

Use meaningful names that represent data to

be stored

First character must be a letter

the underscore character

Remaining characters must be

letters

numbers

underscore character


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Example of identifiers

Identifier Valid Reason if Invalid

TotalSales Yes

_

Total.sales No Cannot contains .

4Qthrsales No Cannot begin with

numberTotal_sales$ No Cannot contain $


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Keyword Keywords (also called reserved words)

Are used by the C++ language

Must be used as they are defined in the

Cannot be used as identifiers

Examples of keyword:

asm class do auto conts break char huge while else case float if far


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Variables declaration (1) Before use, variables must be declared

Tells the compiler the type of data to store

Examples: int number_of_bars;

_ , _

int is an abbreviation for integer.

could store 3, 102, 3211, -456, etc.

number_of_bars is of type integer

double represents numbers with a fractionalcomponent

could store 1.34, 4.0, -345.6, etc.

one_weight and total_weight are both of type double


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Immediately prior to use

At the beginningTwo locations for variable declarations

int main(){

Variables declaration (2)

{int sum;sum = score1 +

score2;

return 0;

}

int sum;sum = score1 + score 2;

return 0;}


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Declaration syntax:

Data_type Variable_1 , Variable_2, . . . ;

Variables declaration (3)

double average, m_score, total_score;

double moon_distance;

int age, num_students;int cars_waiting;


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Assignment statement An assignment statement changes the value of a variable

total_weight = one_weight + number_of_bars; total_weight is set to the sum one_weight + number_of_bars

Assignment statements end with a semi-colon

The single variable to be changed is always on the leftof the assignment operator =

On the right of the assignment operator can be

Constants -- age = 21; Variables -- my_cost = your_cost;

Expressions -- circumference = diameter * 3.14159;


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The = operator in C++ is not an equal sign

The following statement cannot be true in algebra

Assignment statement and Algebra

=

In C++ it means the new value of number_of_bars

is the previous value of number_of_bars plus 3

_ _ _ _


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Exercise 1 Give good variable names for identifiers to store.

the speed of an automobile? an hourly pay rate?

the highest score on an exam?

Identify the following identifiers is valid or not. Net_income

4years_sale

Hour_p#y Year_1income

Y2kilo


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2.2 Understand data types 2 and 2.0 are not the same number

A whole number such as 2 is of type intA real number such as 2.0 is of type double

Numbers of type int are stored as exact values

Numbers of type double may be stored as

approximate values due to limitations on number of

significant digits that can be represented


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Data type (1)Integer (int)

Integer data types hold whole numbers

Type int does not contain decimal points

Examples: 34 45 1 89

a e e ow s ows an n eger a a ypes, s ze an range


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Data type (2)Float/double

The floating-point data types are:

They can hold real numbers such as:

12.45 -3.8Stored in a form similar to scientific notation

All floating-point numbers are signed


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Data type (3) Type float/double can be written in two ways

Simple form must include a decimal point Examples: 34.1 23.0034 1.0 89.9

Data type (3)

Examples: 3.41e1 means 34.13.67e17 means 367000000000000000.0

5.89e-6 means 0.00000589

Number left of e does not require a decimal point

Exponent cannot contain a decimal point


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Example:

Data type (4)


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Character (char)

Used to hold characters or very small integervalues

Data type (5)

Usua y 1 yte o memory Numeric value of character from the character

set is stored in memory:


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Example

Data type (6)


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2.3 : Know operators & expressionPRIMARY EXPRESSION

-

constantIdentifier expression


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ASSIGNMENT EXPRESSION

a =

variable Assignmentoperatorsexpression


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BINARY EXPRESSION

+

Firstoperand

operator Secondoperand


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POSTFIX OPERATOR

operand

a++

Postfix operator

(increment by 1)


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PREFIX EXPRESSION

operand

++a

unary operator


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Operator Can be classified according to:

The type of their operands and their output. Arithmetic

Logical

Boolean

The number of their operand.

Unary(one operand)

Binary(two operands)


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1. Arithmetic Operators (2)


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Arithmetic Operators (1)


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Example of Arithmetic operator



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Exercise 2


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2. Relational Operator (1)


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Relational Operator (2)


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Relational Operator (3)


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3. Logical Operator (1)


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Logical Operator (2)


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Logical Operator (3)


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Formed by combining operators, variables and

constant. Examples:

Expression

ross_pay e uc ons

(basic_pay + hours * rate) (socso + premium + loan)

(b * b 4 * a * c) > 0

(sex == male || sex == female) && age >=21


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Mathematical formula and C expression

Mathematical operator C expression

+ +- -

*

/

OR ||

AND &&NOT !


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Example: Given the following formula

LCF

2832.6

1=

Convert to C expressionF = 1 / (6.2832 * sqrt (L * C))


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Exercise 3 Convert the following equation to C expression:

i. x = m2(m-q) + (p-n)

ii.

iii. -

5

2

= xy

)10

5.5( = xyw

Given integer variables, a = 5, b=7 and c=8, find thefollowing:

a / b + c

a + b x (c / a)

b % a + c

a b + c x (b / a x c)

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