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Fundamental C++ Types

Arithmetic

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C++ has a large number of fundamental or built-in types The fundamental types fall into one of three categories

Integer Floating-point Character

Integer type The basic integer type is int

The size of an int depends on the machine and the compiler On PCs it is normally 16 or 32 bits

Other integers types short: typically uses less bits (often 2 bytes) long: typically uses more bits (often 4 bytes)

Different types allow programmers to use resources more efficiently Standard arithmetic and relational operations are available for these

types

Fundamental C++ Types

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Integer constants Integer constants are positive or negative whole numbers Integer constant forms

Decimal Digits 0, 1, 2, 3, 4, 5, 6, 7

Octal (base 8) Digits 0, 1, 2, 3, 4, 5, 6, 7

Hexadecimal (base 16) Digits 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, a , b, c, d, e, f, A, B, C, D, E, F

Consider 31 oct and 25 dec

Decimal Constants Examples

97 40000 50000 23a (illegal)

The type of the constant depends on its size, unless the type is specified

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Character type

Char is for specifying character data char variable may hold only a single lowercase letter, a single

upper case letter, a single digit, or a single special character like a $, 7, *, etc.

case sensitive, i.e. a and A are not same. ASCII is the dominant encoding scheme

Examples ' ' encoded as 32 '+' encoded as 43 'A' encoded as 65 'Z' encoded as 90 'a' encoded as 97 'z' encoded as 122

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Character type Explicit (literal) characters within single quotes

'a','D','*‘

Special characters - delineated by a backslash \

Two character sequences (escape codes)

Some important special escape codes \t denotes a tab \n denotes a new line \\ denotes a backslash \' denotes a single quote \" denotes a double quote

'\t' is the explicit tab character, '\n' is the explicit new line character, and so on

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Floating-point type

Floating-point type represent real numbers Integer part Fractional part

The number 108.1517 breaks down into the following parts 108 - integer part 1517 - fractional part

C++ provides three floating-point types Float

(often 4 bytes) Declares floating point numbers with up to 7 significant digits

Double long double

(often 10 bytes) Declares floating point numbers with up to 19 significant digits.

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Memory Concepts Variable

Variables are names of memory locations Correspond to actual locations in computer's memory Every variable has name, type, size and value When new value placed into variable, overwrites previous value Reading variables from memory is nondestructive

cin >> integer1; Assume user entered 45

cin >> integer2; Assume user entered 72

sum = integer1 + integer2;

integer1 45

integer2 72

integer1 45

sum 117

integer2 72

integer1 45

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Names (naming entities) Used to denote program values or components

A valid name is a sequence of Letters (upper and lowercase) A name cannot start with a digit

Names are case sensitive MyObject is a different name than MYOBJECT

There are two kinds of names Keywords Identifiers

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Keywords

Keywords are words reserved as part of the language int, return, float, double

They cannot be used by the programmer to name things

They consist of lowercase letters only

They have special meaning to the compiler

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C++ key wordsC++ Keywords

Keywords common to the C and C++ programming languages

auto break case char const

continue default do double else

enum extern float for goto

if int long register return

short signed sizeof static struct

switch typedef union unsigned void

volatile while

C++ only keywords

asm bool catch class const_cast

delete dynamic_cast explicit false friend

inline mutable namespace new operator

private protected public reinterpret_cast

static_cast template this throw true

try typeid typename using virtual

wchar_t

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Identifiers Identifiers are used to name entities in c++ It consists of letters, digits or underscore

Starts with a letter or underscore Can not start with a digit

Identifiers should be Short enough to be reasonable to type

Standard abbreviations are fine (but only standard abbreviations)

Long enough to be understandable When using multiple word identifiers capitalize the first letter of each

word

Examples Grade Temperature CameraAngle IntegerValue

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Definitions/declaration

All objects (or variable) that are used in a program must be defined (declared) An object definition specifies

Type Identifier

General definition form

Type Id, Id, ..., Id;

Knowntype

List of one ormore identifiers

(Value of an object is whatever is in its assigned memory location)

Examples

Char Response;int MinElement;float Score;float Temperature;int i;int n;char c;float x;

Location in memory where a value can be stored for program use

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Type compatibilities

Rule is to store the values in variables of the same type This is a type mismatch:

int int_variable;

int_variable = 2.99;

If your compiler allows this, int variable willmost likely contain the value 2, not 2.99

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Stream extraction and assignment operator

>> (stream extraction operator) When used with cin, waits for the user to input a value and stores

the value in the variable to the right of the operator The user types a value, then presses the Enter (Return) key to

send the data to the computer Example:

int myVariable;cin >> myVariable;

Waits for user input, then stores input in myVariable = (assignment operator)

Assigns value to a variable Binary operator (has two operands) Example:

sum = variable1 + variable2;

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A simple program to add two numbers

1 //example

2 // program to add two numbers

3 #include <iostream.h>

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5 int main()

6 {

7 int integer1, integer2, sum; // declaration

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9 cout << "Enter first integer\n"; // prompt

10 cin >> integer1; // read an integer

11 cout << "Enter second integer\n"; // prompt

12 cin >> integer2; // read an integer

13 sum = integer1 + integer2; // assignment of sum

14 cout << "Sum is " << sum << endl; // print sum

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16 return 0; // indicate that program ended successfully

17 }

•Notice how cin is used to get user input. General form is cin>>identifier;

•Cin is an I stream object•streams input from standard input•uses the >> (input operator)•Note that data entered from the keyboard must be compatible with the data type of the variable

endl flushes the buffer and prints a newline.

•Variables can be output using cout << variableName.•Generl form is cout<<expression;•An expression is any c++ expression(string constant, identifier, formula or function call)•Cout is an o stream object•streams output to standard output•uses the << (output) operator

Calculations can be performed in output statements: alternative for lines 13 and 14:

cout << "Sum is " << integer1 + integer2 << std::endl;

Use stream extraction operator with standard input stream to obtain user input.

Concatenating, chaining or cascading stream insertion operations.

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Output of program

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program to find the area of rectangle

Tells the compiler to use names in iostream in a “standard” way

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output

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Program to find total number of students in all sections

1. //example2. //to find the total number of students in all sections.

3. # include <iostream> //preprocessor directive4. int main()5. {6. int number_of_sections, students_per_section; //declaration7. int total_students; 8. cout<<"enter the number of sections\n"; //prompt to enter total number of

sections9. cin>>number_of_sections; //reading number of sections10. cout<<"enter the number of students per section\n"; //prompt to enter number 11. // of students per section

12. cin>>students_per_section; //reading students per section13. 14. total_students = number_of_sections * students_per_section; //assignment to total

students15. cout<<"total number of students in all the sections is\n"; //prompt16. cout<<total_students; // show the number of total

students

17. return 0;18. }

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output

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Arithmetic Arithmetic is performed with operators. Arithmetic operators are listed in following table

Modulus operator returns the remainder of integer division 7 % 5 evaluates to 2

Integer division truncates remainder 7 / 5 evaluates to 1

C++ operation Arithmetic operator

Algebraic expression

C++ expression

Addition + f + 7 f + 7

Subtraction - p – c p - c

Multiplication * bm b * m

Division / x / y x / y

Modulus % r mod s r % s

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Results of Arithmetic operators

Arithmetic operators can be used with any numeric type.

An operand is a number or variable used by the operator e.g. integer1 + integer2

+ is operator integer1 and integer2 are operands

Result of an operator depends on the types of operands If both operands are int, the result is int If one or both operands are double, the result is double

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Examples comparing mathematical and C++ expressions

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Operator precedence Some arithmetic operators act before others

(e.g., multiplication before addition) Be sure to use parenthesis when needed

Example: Find the average of three variables a, b and c

Do not use: a + b + c / 3 (incorrect) Use: (a + b + c ) / 3 (correct)

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Rules of operator precedence

Operator(s) Operation(s) Order of evaluation (precedence)

() Parentheses Evaluated first. If the parentheses are nested,

the expression in the innermost pair is evaluated

first. If there are several pairs of parentheses “on

the same level” (i.e., not nested), they are

evaluated left to right.

*, /, or % Multiplication Division Modulus

Evaluated second. If there are several, they are evaluated left to right.

+ or - Addition Subtraction

Evaluated last. If there are several,

they are evaluated left to right.

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Operator Precedence

An example to understand operator precedence.

20 - 4 / 5 * 2 + 3 * 5 % 4

(4 / 5)

((4 / 5) * 2)

((4 / 5) * 2) (3 * 5)

((4 / 5) * 2) ((3 * 5) % 4)

(20 -((4 / 5) * 2)) ((3 * 5) % 4)

(20 -((4 / 5) * 2)) + ((3 * 5) % 4)

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Assignment operators = is the assignment operator Used to assign a value to a variable An assignment statement changes the value of a variable General Form:

identifier = expression;

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

On the right of the assignment operator can be Constants

For example age = 21; Variables

For example my_cost = your_cost; Expressions

For example circumference = diameter * 3.14159;

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Assignment operators

The ‘=‘ operator in C++ is not an equal sign The following statement cannot be necessarily true in algebra

number_of_bars = number_of_bars + 3;

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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Assignment expression abbreviations Program can be written and compiled a bit faster by the use of abbreviated

assignment operators C++ provides several assignment operators for abbreviating assignment

expressions. Addition assignment operator

c = c + 3; abbreviated to c += 3;

Statements of the formvariable = variable operator expression;

can be rewritten asvariable operator= expression;

Other assignment operatorsd -= 4 (d = d - 4)e *= 5 (e = e * 5)f /= 3 (f = f / 3)g %= 9 (g = g % 9)

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Arithmetic assignment operators

Assignment operator

Sample expression

Explanation Assigns

Assume: int c = 3, d = 5, e = 4, f = 6, g = 12;

+= c += 7 c = c + 7 10 to c

-= d -= 4 d = d - 4 1 to d

*= e *= 5 e = e * 5 20 to e

/= f /= 3 f = f / 3 2 to f

%= g %= 9 g = g % 9 3 to g

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Increment and Decrement Operators Increment and decrement operators are unary operators as they

require only one operand.

++ unary increment operator Adds 1 to the value of a variable

x ++; is equivalent to x = x + 1;

Pre-increment When the operator is used before the variable (++c) Variable is changed, then the expression it is in is

evaluated Post-increment

When the operator is used after the variable (c++) Expression the variable is in executes, then the variable is

changed.

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Increment and Decrement Operators

-- -- unary decrement operator Subtracts 1 from the value of a variable

x --;is equivalent to x = x – 1;

Pre-decrement When the operator is used before the variable (--c) Variable is changed, then the expression it is in is

evaluated. Post-decrement

When the operator is used after the variable (c--) Expression the variable is in executes, then the variable is

changed.

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Increment and Decrement Operators Example If c = 5, then

cout << ++c; c is changed to 6, then printed out

cout << c++; Prints out 5 (cout is executed before the increment) c then becomes 6

When variable not in expression Preincrementing and postincrementing have same effect

++c; cout << c;

and c++; cout << c;

are the same

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Summarizing increment and decrement operators in a table

Operator Called Sample expression Explanation

++ preincrement ++a Increment a by 1, then use the new value

of a in the expression in which a resides.

++ postincrement a++ Use the current value of a in the expression

in which a resides, then increment a by 1.

-- predecrement --b Decrement b by 1, then use the new value

of b in the expression in which b resides.

-- postdecrement b-- Use the current value of b in the expression

in which b resides, then decrement b by 1.

The associativity of these unary operators is from right to left

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An example to understand the effect of pre-increment and post-increment

1 // example 2 // Pre incrementing and post incrementing.3 #include <iostream.h>4 5 8 // function main begins program execution9 int main()10 {11 int c; // declare variable12 13 // demonstrate pos tincrement14 c = 5; // assign 5 to c15 cout << c << endl; // print 516 cout << c++ << endl; // print 5 then post increment17 cout << c << endl << endl; // print 6 18 19 // demonstrate pre increment20 c = 5; // assign 5 to c21 cout << c << endl; // print 522 cout << ++c << endl; // pre increment then print 6 cout << c << endl; // print 6 24 25 return 0; // indicate successful termination26 27 } // end function main

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output

Cout<<c prints c =5Cout<<c++ prints c =5 then increment c by 1 to 6Cout<<c prints c =6

Cout<<c prints c =5Cout<<++c first increment c by one to to 6 then prints c =6 Cout<<c prints c =6

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Precedence of the operators encountered so far

Operators Associativity Type

() left to right parentheses

++ -- static_cast<type>() left to right unary (postfix)

++ -- + - right to left unary (prefix)

* / % left to right multiplicative

+ - left to right additive

<< >> left to right insertion/extraction

< <= > >= left to right relational

== != left to right equality

?: right to left conditional

= += -= *= /= %= right to left assignment

, left to right comma