Cheatsheets
Learn C: Variables and Operators

Learn C: Variables and Operators

Understanding Variables

Naming Variables in C

Variable names in C must start with a letter or an underscore, followed by letters, numbers, or underscores. They cannot start with a number and should not be a reserved word in C.

                                
// Valid variable names
int age;
float _price;
int total1;

// Invalid variable names
int 1stNumber;
float double;

Common Data Types in C

In C, the main data types are used to specify what kind of data a variable can hold. The most common types are: - `int` for integers (whole numbers) - `float` for single-precision floating-point numbers (decimals) - `double` for double-precision floating-point numbers (more precise decimals) - `char` for single characters (like letters)

                                
// Declaring variables with different data types
int count = 10;
float price = 9.99;
double balance = 1000.50;
char grade = 'A';

Initializing Variables in C

You can set a value to a variable when you declare it, or you can assign it a value later in the code. Initializing a variable means giving it a starting value.

                                
// Initializing a variable at declaration
int age = 25;

// Assigning a value to a variable later
int age;
age = 25;

Converting Between Data Types

Sometimes you need to convert a variable from one data type to another. This can be done explicitly by using a cast or implicitly by the compiler.

                                
// Explicit conversion (casting)
float price = 9.99;
int roundedPrice = (int)price; // roundedPrice will be 9

// Implicit conversion
int number = 10;
float decimal = number; // decimal will be 10.0

Understanding Operators

Basic Math Operators

In C, you can perform basic arithmetic operations using symbols. These symbols help you add, subtract, multiply, and divide numbers.

                                
// Basic math operations
int sum = 5 + 3;       // Addition
int difference = 5 - 3; // Subtraction
int product = 5 * 3;    // Multiplication
int quotient = 5 / 3;   // Division

Shorthand for Assignment and Math

C provides shorthand operators that combine assignment with a basic arithmetic operation. These operators make code shorter and often clearer.

                                
// Shorthand operators
int x = 10;
x += 5; // Equivalent to x = x + 5;
x *= 2; // Equivalent to x = x * 2;

Comparing Values

C allows you to compare two values using comparison operators. These operators return true or false based on whether the comparison is true.

                                
// Comparison operators
int a = 5;
int b = 10;

bool isEqual = (a == b); // false
bool isGreater = (a > b); // false
bool isLess = (a < b); // true

Logical Operators

Logical operators are used to combine multiple conditions. They help in making decisions based on multiple criteria.

                                
// Logical operators
bool result1 = (5 > 3) && (8 < 10); // true (both conditions are true)
bool result2 = (5 > 3) || (8 > 10); // true (one condition is true)
bool result3 = !(5 > 3); // false (negation of the condition)

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