Variables and Data Types in Programming

Variables

• A variable is a named storage location that holds a value.
• Variables have a name, data type, and value.
• Variables are used to store and manipulate data in a program.
• Examples of variable declarations:
  • int x = 5; (integer variable)
  • string name = "John"; (string variable)
  • float pi = 3.14; (float variable)

Data Types

• A data type determines the type of value a variable can hold.
• Common data types:
  • Integers (int): whole numbers, e.g. 1, 2, 3
  • Floating-point numbers (float): decimal numbers, e.g. 3.14, -0.5
  • Characters (char): single characters, e.g. 'a', 'B'
  • Strings (string): sequences of characters, e.g. "hello", "goodbye"
  • Boolean (bool): true or false values
  • Arrays (array): collections of values of the same data type
  • Objects (object): complex data types that can hold multiple values

Functions

• A function is a block of code that performs a specific task.
• Functions have a name, parameters, and a return value.
• Functions can be reused throughout a program.
• Examples of functions:
  • add(x, y): takes two integer parameters and returns their sum
  • greet(name): takes a string parameter and returns a greeting message

Object Oriented Programming

• Object-oriented programming (OOP) is a programming paradigm that organizes code into objects.
• An object represents a real-world entity or concept.
• Objects have properties (data) and methods (functions).
• Key concepts:
  • Classes: define the structure and behavior of objects
  • Inheritance: a child class inherits properties and methods from a parent class
  • Polymorphism: objects of different classes can be treated as if they were of the same class
  • Encapsulation: objects hide their internal state and expose only necessary information

Control Structures

• Control structures determine the flow of a program's execution.
• Common control structures:
  • Conditional statements (if/else):
    • if (condition) { code }: executes code if condition is true
    • if (condition) { code } else { code }: executes code if condition is true, otherwise executes alternative code
  • Loops (for, while, do-while):
    • for (init; condition; increment) { code }: executes code repeatedly while condition is true
    • while (condition) { code }: executes code repeatedly while condition is true
    • do { code } while (condition): executes code repeatedly while condition is true
  • Jump statements (break, continue, return):
    • break: exits a loop or switch statement
    • continue: skips to the next iteration of a loop
    • return: exits a function and returns a value

Variables

• A variable is a named storage location that holds a value.
• Variables have a name, data type, and value.
• Variables are used to store and manipulate data in a program.
• Variable declarations involve specifying the data type and assigning a value.

Data Types

• A data type determines the type of value a variable can hold.
• Common data types include:
  • Integers (int): whole numbers, e.g. 1, 2, 3
  • Floating-point numbers (float): decimal numbers, e.g. 3.14, -0.5
  • Characters (char): single characters, e.g. 'a', 'B'
  • Strings (string): sequences of characters, e.g. "hello", "goodbye"
  • Boolean (bool): true or false values
  • Arrays (array): collections of values of the same data type
  • Objects (object): complex data types that can hold multiple values

Functions

• A function is a block of code that performs a specific task.
• Functions have a name, parameters, and a return value.
• Functions can be reused throughout a program.
• Functions can take parameters, which are values passed to the function when it is called.
• Functions can return a value, which can be used in the program.

Object Oriented Programming

• Object-oriented programming (OOP) is a programming paradigm that organizes code into objects.
• An object represents a real-world entity or concept.
• Objects have properties (data) and methods (functions).
• Key concepts in OOP include:
  • Classes: define the structure and behavior of objects
  • Inheritance: a child class inherits properties and methods from a parent class
  • Polymorphism: objects of different classes can be treated as if they were of the same class
  • Encapsulation: objects hide their internal state and expose only necessary information

Control Structures

• Control structures determine the flow of a program's execution.
• Common control structures include:
  • Conditional statements (if/else): used to make decisions in a program
  • Loops (for, while, do-while): used to repeat code
  • Jump statements (break, continue, return): used to control the flow of a program
• Conditional statements can be used to execute different blocks of code based on conditions.
• Loops can be used to execute code repeatedly while a condition is true.
• Jump statements can be used to exit a loop or function, or to skip to the next iteration of a loop.