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Intro

This is my attempt to learn and document C++, While following the text: “C++ Program Design
An Introduction To Programming and Object-Oriented Design”

Prerequisite

My Current Set up :

• Windows 11
• Vs Code (with C++ Extensions Enabled)
• C++ Compiler

Hello World

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#include <iostream>
#include <string>
using namespace std;
int main() {
    cout << "Hello, World!" << endl;
    return 0;
}

• The top 3 lines will start almost all programs in C++

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#include <iostream>
#include <string>
using namespace std;

• This shows that program will use the iostream library to do inputs and outputs.
• Line 1 and 2 are know as a preprocessor which are programs that run before the compiler.
• Line 3 Indicates that the program will be using objects that are named in a special region called std

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int main()

• Line 4 is know as a function which specifies the return value
• The main method is the first function that is called when the program is compiled and executed.
• The Word “Int” indicates the return type I this case Int is Integer. in C++ the main method will always return and int.
• The word “main” is the name of the method
• The () are used to delimit any arguments, in this case the main method does not require arguments.
• The { } group together statements, and in this case this these statements make up the function.

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cout << "Hello, World!" << endl;
return 0;

• The first statement starts with cout which is an object that indicates an output stream
• The << inserts a element in this case to the output stream
• Following this we have “Hello World” this is out output string that would display when the program is run.
• Then the end of the first statement is end with endl this is know as a manipulator and this indicates a new line.
• The second statement “return 0;” would be returned by the main method, a zero indicates that the program ran without issues.
• A non zero output would mean that there was some error with the execution of the method.

User Inputs

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#include <iostream>
#include <string>
using namespace std;
int main() {
    // cout << "Hello, World!" << endl;  
    cout << "Purchase price ?";
    float Price;
    cin >> Price;

    //compute the output sales tax
    cout << "Sales tax on $" << Price << " is ";
    cout << "$" << Price * 0.04 << endl;
    return 0;
}

• The following ask the user for the input to calculate the sales tax of a purchase.

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float Price;

• Here im creating a variable that will store the Price as a floating point number.
• this is because the expected input could be a number with a decimal place (ex. 5.99).

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cin >> Price;

• Cin is an object like cout, however Cin is an input stream
• The users input value is converted to the internal format for floating point number and stores in the Price object.

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cout << "Sales tax on $" << Price << " is ";
cout << "$" << Price * 0.04 << endl;

• The last statements will output the price then followed by the calculated sales tax.

Comments

• Comments is a mechanism that allows programmers to add prose or comments in code
• Comments are ignored by the compiler, generally used to describe what a piece of code is doing.

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// Here is a comment that span one line 
/* This a comment that can span 
MULTIPLE

LINES

*/

Objects

Integer

• In C++ the basic integer type is called an int
• The compiler and underling hardware determine the size of int
  • for example most pc support size of 16 bits, where int can represent integers from -32768 - 32768
  • for unix it would be 32 bits and newer system can support up to 64 bit integers.
• There are also several other integer object types like short and long
  • C++ does not determine the size of short or long however it does specfy the following:
    NumberOfBits_short $\leq$ NumberOfBits_int $\leq$ NumberOfBits_long

Character

• Closely related to integer object the character object (CHAR) are represented by integers

• ASCII is a character set that is used for computers to interpret characters based on a corespondent number.

• because characters can be represented as number the following will always be true
  ‘a’ < ‘b’ < ‘c’ < ….. < ‘z’
  ‘A’ < ‘B’ < ‘C’ < ….. < ‘Z’
  and
  ‘0’ < ‘1’ < ‘2’ < ….. < ‘9’

• this is relationship is useful as it allows characters to be sorted, ex. alphabetically , etc..

Floating Point

• Floating points object are used to represent real numbers, that is, numbers that have both an integer part and a fractional part.
  Ex. 3.1412

• C++ comes with support for the 3 types of floating point numbers

  1. Float
  2. Double
  3. Long Double

• and these types are represented as subsets of one and other so:
  Float is a subset of double and double is a subset of long double

Constants

String and character constants

• String constants is a sequence of zero or more characters enclosed in double quotes

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" Hello World " 

• there are also characters know as escape characters:

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"Hello World!\n"

• here the \n would indicate that the character n is not a character but rather should be interpreted as a new line.

Integer constants

• The simplest way to write an integer constant in C++ would be to write:

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23 45 125 990

• by default an integer would be interpreter by C++ as an int
• you can append a l or L at the end of a number to treat a number as a long

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23L 45L 125L 990L

• If an integer constant does not have a suffix the compiler will choose the type depending on the size
• It will try int first and if the number is to big then it will try to store it in a long
• and if the value is still to long it will through an error

Floating point constants

• layout for floating point constants
  digits.digits[f | F | l | L]

• the constant will consist of:

  1. sequence of number before the .
  2. sequence of numbers after the .
  3. optional type specifiers
  4. also 1 or 2 could be omitted (ex. 0.5 or 1.0)

• like integers constants float constants by default are read as double unless otherwise specified

• the suffix option are as follows:

  1. f, F = float
  2. l, L = long double

• in C++ floating point numbers can be represented in scientific notation:
  1.23x10[^3]

  which is read as

  1230.0

• the general for is a followed
  mantissa x 10 [^exponent]

  and the syntax is a follows

  Digits.Digits[Exponent] [f | F | l | L]

either the whole part or fraction part can be omitted, but not both

where the exponent is 

(e | E) [+ | -] Digits 

• The mantissa can be an integer or a decimal number. The expoents is a signed integer.
  Ex: 1.23E10 , 0.23E-4, 45.e+23, 23.68E12

Keywords

• keywords have special meaning to the compiler and they CANNOT be changed by the programmer.
• these are also case sensitive, which consist of lowercase letters only.

Identifiers

• names that are defined by the programmer
• the rule for forming a valid identifier name is that it must be valid c++ name and cannot clash with any of the existing keywords.
  ex. n, price, x, numberOfPeople, getName, ….. etc
• use clear and human readable name for the identifiers so that it helps with code readability.

Definition

• To use an object in C++ you must first define the object

a Common form of a C++ definition is
Type Id, Id, ….., Id;

ex: int Sum;

• Here I defined an integer object who identifier is Sum;
• Also in this case the object is defined with no initial value, however memory is still allocated for the creation of this object.
  Other ex:
  • int x
  • int WordCnt, Radius, Height;
  • float FlightTime, Mileage, Speed;
• all of the above are defined but not initialized.
• generally it not recommend to define and not assign some value to an object as that could lead to an unified error.

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#include <iostream>
#include <string>
using namespace std;
    int main() {
        float f;
        char c;
        int i;
        double d;
        cout << "f's value is " << f << endl;
        cout << "i's value is " << i << endl;
        cout << "c's value is " << c << endl;
        cout << "d's value is " << d << endl;

        return 0;
    }

• when the following is executed, the program outputs

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f's value is 1.81825e+11
i's value is 8653
c's value is e 
d's value is 1.12975e-231

• As you can see the output can be unpredictable if objects are not initialized.
• Another form of definition allows objects to be initialized when they are defined
  Type Id = Const, Id = Const ….., Id = Const;
• In practice it is:
  int Sum = 0;
  float TaxRate = 0.06;
  char Letter = ‘a’;

Expressions

Simple Expression

• The simplest form of the C++ expression is a constant with no operation applied
  ex.
  23;
• Here the results yields <23, int>, and the ; after the expression is the C++ delimiter that separates or terminates an expression.
  ex.
  ‘a’;
• Here the results yields <97, int>
• An expression can also be an object with no operation applied. The result of evaluating this type of expression is the value of the object.
  ex.
  int XCoord = 23;
  XCoord;
• The result of evaluating the expression is <23, int>. In some sense, an operation is being applied to the operand XCoord. The operation being applied is one that fetches the value stored in XCoord.

Binary arithmetic operations

• Arithmetic operations for integers