C++ Variables and Data Types

Study Notes

Integers and Floating-Point Numbers

Integers represent whole numbers (positive, negative, or zero), like 10, -5, 0. Floating-point numbers represent numbers with decimal parts, like 3.14, -2.5, 0.0.
C++ stores integers directly; no special formatting (commas, spaces) is needed.
Negative integers are represented using the two's complement method.
Octal (base-8) and hexadecimal (base-16) notations are used to represent integers differently (e.g., 010 octal, 0xA hex).

Variables in C++

A variable is a named storage location that holds a value. It has a name, type, and value.
Variable names must adhere to rules:
- Only letters, digits, and underscores are permitted.
- Names must begin with a letter or underscore.
- C++ is case-sensitive (myVar and myvar are different).
Examples:
- Valid: count, _total, price1
- Invalid: 2count, total!, count-1

Variable Declaration

To create a variable, you must declare its type and name.
Syntax: data_type variable_name;
Example: int age; declares an integer variable named age.
Multiple variables of the same type can be declared on the same line: int x, y, z;

Value Assignment

The assignment operator (=) assigns a value to a variable. variable_name = value;
Example: age = 30;
Assignment is different from comparison (==). x = 5 assigns 5 to x, while x == 5 checks if x is equal to 5.

Reserved Keywords

Keywords are reserved words with predefined meanings in C++. They cannot be used as variable names.
Example: int, float, if, else
Keywords are case-sensitive.

Comments in Code

Comments explain the purpose of your code.
Line comments start with //.
Block comments start with /* and end with */.

Example:

// This is a line comment
/* This is a block comment
spanning multiple lines */

Nesting comments is not allowed (e.g., /* /* */ */).

Practical Application (LAB)

Scenario: Improve this poorly-formatted code.

// Function to calculate area
// This is extra, unnecessary comment
int area (int length, int width){
   // Calculat area
  int area =  length* width;
   // return the calculated area
  return area;
}

Improvements:
- Remove redundant comments.
- Improve variable names (e.g., length to rectangleLength).
- Add or edit comments where needed for clarity (e.g., explaining the calculation).
- Use consistent formatting for readability (e.g., add white space).

Description

Test your knowledge on integers, floating-point numbers, and variable declaration in C++. This quiz covers the rules for naming variables and the different ways to represent integers in C++. Challenge yourself with concepts fundamental to programming in C++!