Variables Types Operators

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Variables, Types & Operators

Object-Oriented Programming in C++

(ICTCO10306)

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Simple C++ Program#include

using namespace std; //

int main()

{

// Declarations

// Statements

return 0;}

Fromlastweek

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Sample C++ Program#include

using namespace std; void main()

{

int number;

cout number;cout


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Did you try this?

Problem: To determine the average of threenumbers

Task: Request, from the user, three numbers,compute the average of the three numbers,and print out the original values and thecomputed average

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Declaring a Variable

Variable provides you a named storage in Computer Memory

Declaring a variableint number;

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Type Identifier (This is the name we give toThe variable)


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Identifiers

Valid Identifierssequence of one or more letters, digits or

underscore characters (_)Neither spaces nor punctuation marks orsymbols can be part of an identifier

Are there invalid identifiers?

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Reserved words You cannot use any of these as an identifierasm, auto, bool, break, case, catch, char, class,const, const_cast, continue, default, delete, do,double, dynamic_cast, else, enum, explicit, export,extern, false, float, for, friend, goto, if, inline, int,long, mutable, namespace, new, operator, private,protected, public, register, reinterpret_cast, return,short, signed, sizeof, static, static_cast, struct,

switch, template, this, throw, true, try, typedef,typeid, typename, union, unsigned, using, virtual,void, volatile, wchar_t, while

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Identifiers

Identifiers are case sensitiveExample

Int year;Int Year; // these are identified as two differentvariables by C++ compiler

Always try to give meaningful phrases as identifiers

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Data type for the variable

Try this in C++ using int variables A = 5

B = 2C = A / B ?

What data type is suitable for this application?

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Fundamental Data Types in

C++

Try again with the suitable data type

Source http://www. cplusplus.com 11


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Signed (+/-) Vs. UnsignedExamples

unsigned short int number_of_people;

signed int my_mccount_balance; //is thiscorrect?short int Year;

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String of Characters as a

single variableWhat is a string

Set of characters placed in order

A special type of variable to store a completestring of charactedsCannot be handled by

Iostream.h

You need < string.h >

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Initializing a Variable

Why Initialize?There can be stray values / residuals from

previous programsExample:int a = 0;

It is a good programming practice to intialize avariable as soon as you declare it

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Initializing a Variable

How do you initialize a variable?Int a = 5;

Int b(5);Both methods are valid in c++

Variables a and b will be initialized to value 5

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Where do you declare a variable?

1. Definitely before you use them1. Within the main function2. Before the main functionExample:#include

short unsigned int year = 2013;

int main()

{

short unsigned int month;

month = 11;

cout


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Scope of a variable

short unsigned int year = 2013;This is a Global Variable (Visible everywhere in

the program)short unsigned int month;This is a local variable (Can use only in mainfunction)

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Example:#include Using namespace std;short unsigned int year = 2013;// Global variableint main()

{short unsigned int month;// Local variablemonth = 11;cout


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Operators in C++

Name the operators you already know

Exampleint a,b;a = 2 + (b = 5);a = b = 5;

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Arithmetic operators

+ Addition- Subtraction* Multiplication

/ Division% Modulo division (Remainder of the division)

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Compound AssignmentUsing these you can reduce length of codesUsed to modify value of a variable

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expression is equivalent tovalue += increase; value = value + increase;

a -= 5; a = a - 5;

a /= b; a = a / b;

price *= units + 1; price = price * (units +1);


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Increase and decrease(++, --)

Also called increment and decrement operatorsExample

C++;++C; // These are different operations

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Example 1 Example 2

B=3;A=++B;// A contains 4, B contains 4

B=3;A=B++;// A contains 3, B contains 4


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Relational and equality operators

Comparison between values or variables

Do not confuse between == and = operatorsEvaluate the expression: ((b=2) == a)

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== Equal to

!= Not equal to

> Greater than

< Less than>= Greater than or equal to


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Relational and equality operators

Comparison between values or variables

Do not confuse between == and = operatorsEvaluate the expression: ((b=2) == a)

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== Equal to

!= Not equal to

> Greater than

< Less than>= Greater than or equal to


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Comma Operator

A = (B=3, B+2);1. Will assign B=3;2. Then evaluate a = B+2

This is equivalent toB=3;

A=B+2;

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Logical Operations: And(&&)

A && BExpression is Trueiff A and B areboth true

T F

T T F

F F F

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Logical Operations: Or(||)

A || BExpression is Trueif either A or B areTrueNote: Also True

when A and B areboth True

T F

T T T

F T F

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Logical Operations: Exercises

A = 1, B = 1, C = 01. A || B2. A && C3. A || B && C

4. ( (5 == 5) && (3 > 6) ) 29


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Precedence of operators

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Level Operator Description Grouping

1 :: scope Left-to-right

2() [] . -> ++ -- dynamic_cast static_castreinterpret_cast const_cast typeid

postfix Left-to-right

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++ -- ~ ! sizeof new delete unary (prefix)

Right-to-left* &indirectionand reference(pointers)

+ -unary signoperator

4 (type) type casting Right-to-left

5 .* ->* pointer-to-member

Left-to-right

6 * / % multiplicative Left-to-right

7 + - additive Left-to-right

8 > shift Left-to-right


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Precedence of operators

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9 < > = relational Left-to-right

10 == != equality Left-to-right

11 & bitwise AND Left-to-right

12 ^ bitwise XOR Left-to-right

13 | bitwise OR Left-to-right

14 && logical AND Left-to-right

15 || logical OR Left-to-right

16 ?: conditional Right-to-left

17= *= /= %= += -= >>=

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Variables Types Operators