C++ Programming Study Notes

C++ Output

• C++ Output (Print Text):

  • The cout object is used along with the << operator to output values and print text.

  • Syntax:

  • Surround the text to be printed with double quotes (" ").

  • Example: cout << "Hello, World!";

  • Multiple cout objects:

  • You can concatenate multiple cout calls, but it does not automatically insert a new line at the end.

C++ Print Numbers

• Printing Numbers:

  • You can use cout to print numerical values.

  • Important Note:

  • Unlike text, numbers should not be enclosed in double quotes.

  • Example: cout << 10;

  • Mathematical Calculations:

  • You can perform calculations within the cout statement as well.

New Lines

• Inserting New Lines:

  • Use the newline escape character \n to insert a new line in output.

  • Syntax Example: cout << "Hello \nWorld!";

  • Alternatively, use endl manipulator for a new line:

  • Example:
    cpp cout << "Hello World!" << endl; cout << "I am learning C++";

  • Behavior of \n:

  • The newline character (\n) forces the cursor to move to the beginning of the next line on the screen, resulting in a new line.

Escape Sequences

• 
  

• Common Escape Sequences:
  

  Escape Sequence	Description
  \t	Creates a horizontal tab
  \\	Inserts a backslash character ()
  \"	Inserts a double quote character
  Comments

  • Purpose of Comments:

    • Comments serve to explain and clarify C++ code, enhancing readability.

    • Used for testing by preventing execution of certain code sections.

  • Types of Comments:

    • Comments can be either single-lined or multi-lined.

  Single-line Comments

  • Syntax:

    • Start with two forward slashes (//). Everything following will be ignored by the compiler.

    • Example:
      cpp // This is a single line comment cout << "Hello!";

  Multi-line Comments

  • Syntax:

    • Start with /* and end with */. Everything between these markers will be ignored.

    • Example:
      cpp /* This is a multi-line comment cout << "Hello!"; */

  C++ User Input

  • Input Using cin:

    • cin is a predefined object used to read data from the keyboard, employing the extraction operator (>>).

    • Example:
      cpp int x; cin >> x; cout << "You entered: " << x;

  • Pronunciation:

    • cout is pronounced "see-out" and is used for output (using <<).

    • cin is pronounced "see-in" and is used for input (using >>).

  C++ iostream Objects

  • Overview:

    • The <iostream> library provides objects that can read user input and produce output data either to the console or to files.

  C++ Data Types

  • Declaring Variables:

    • A variable in C++ must have a specified data type.

    • Examples of Data Type Declarations:

    • int myNum = 5;

    • float myFloatNum = 5.99;

    • double myDoubleNum = 9.98;

    • char myLetter = 'D';

    • bool myBoolean = true;

    • string myText = "Hello";

  • Types of Data:

    • Integer: Whole numbers (e.g., 5)

    • Float: Floating point numbers (e.g., 5.99)

    • Double: More precision than float (e.g., 9.98)

    • Character: Single characters (e.g., 'A')

    • Boolean: True or false values

    • String: Sequence of characters (e.g., "Hello")

  Basic Data Types

  • 
    

  • Description of Basic Data Types:
    

    Data Type	Size	Description
    boolean	1 byte	Stores true or false values
    char	1 byte	Stores a single character/letter/number
    int	2 or 4 bytes	Stores whole numbers, without decimals
    float	4 bytes	Stores fractional numbers, sufficient for 6-7 decimal digits
    double	8 bytes	Stores fractional numbers, sufficient for 15 decimal digits
    C++ Numeric Data Types

    • Usage Guidelines:

      • Use int for whole numbers (e.g., 35, 1000).

      • Use float or double for floating-point numbers (e.g., 9.99, 3.14515).

    Float vs. Double

    • Precision Differences:

      • float precision: 6-7 decimal digits.

      • double precision: about 15 decimal digits.

      • It is generally safer to use double for most calculations due to its greater precision.

    Scientific Numbers

    • Using Scientific Notation in Floating Points:

      • A floating-point number can be written in scientific notation using an "e" to denote the power of 10.

      • Example:
        cpp float scientificNum = 1.23e10; // equivalent to 1.23 * 10^10

    Boolean Types

    • Definition:

      • A boolean data type is declared using the bool keyword.

      • It can take only two values: true or false.

      • When returned, true corresponds to 1 and false to 0.

    • Application:

      • Boolean values are predominantly used for conditional testing.

    Character Types

    • Character Storage in C++:

      • The char data type stores a single character.

      • Characters must be surrounded by single quotes (e.g., 'A', 'c').

      • Alternatively, ASCII values can represent characters.

    String Types

    • Storing Text:

      • The string type is used for sequences of characters (text).

      • Strings must be surrounded by double quotes (e.g., "Hello").

      • To use string types, include the <string> library in your source code:
        cpp #include <string>

    The auto Keyword

    • Functionality:

      • The auto keyword automatically identifies a variable's type based on the assigned value.

      • It enables cleaner code and reduces redundancy in long or complex types.

      • Example:
        cpp auto x = 5; // 'x' is automatically inferred as int

    Important Notes on auto

    • Requirements:

      • auto must be assigned a value at the time of its declaration.

      • Example:
        cpp auto x; // This is incorrect, as 'x' must be initialized

    • Stability of Type:

      • Once the type is determined, it remains constant:
        cpp auto x = 5; // 'x' is now int x = 10; // OK x = 9.99; // Error, cannot assign double to int