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Learn C#: Numbers and Operators

Console.ReadLine()

The Console.ReadLine() method is used to get user input. The user input can be stored in a variable. This method can also be used to prompt the user to press enter on the keyboard. 

Console.WriteLine("Enter your name: "); 
 
string name = Console.ReadLine();

Comments

Comments are bits of text that are not executed. These lines can be used to leave notes and increase the readability of the program.

  • Single line comments are created with two forward slashes //.
  • Multi-line comments start with /* and end with */. They are useful for commenting out large blocks of code.
// This is a single line comment


/* This is a multi-line comment
   and continues until the end
   of comment symbol is reached */

Console.WriteLine()

The Console.WriteLine() method is used to print text to the console. It can also be used to print other data types and values stored in variables.

Console.WriteLine("Hello, world!");


// Prints: Hello, world!

Arithmetic Operators

Arithmetic operators are used to perform basic mathematical operations on numerical values:

  • + addition operator
  • - subtraction operator
  • * multiplication operator
  • / division operator
  • % modulo operator (returns the remainder)
int result; 


result = 10 + 5;  // 15


result = 10 - 5;  // 5


result = 10 * 5;  // 50


result = 10 / 5;  // 2


result = 10 % 5;  // 0

String Interpolation in C#

String interpolation provides a more readable and convenient syntax to create formatted strings. It allows us to insert variable values and expressions in the middle of a string so that we don’t have to worry about punctuation or spaces.

int id = 100


// We can use an expression with a string interpolation.
string multipliedNumber = $"The multiplied ID is {id * 10}.";


Console.WriteLine(multipliedNumber);
// This code would output "The multiplied ID is 1000."

Built-in Math Methods

In C#, Math provides many built-in methods for performing advanced mathematical operations. Some common methods include:

  • Math.Abs() — calculates the absolute value of a given number
  • Math.Sqrt() — calculates the of a given number
  • Math.Floor() — rounds the given number down to the nearest integer
  • Math.Min() — takes 2 values of the same type and returns the value that is less
double x = -80; 


double absValue = Math.Abs(x); // 80
double sqRoot = Math.Sqrt(absValue); // 8.94427190999916
double floored = Math.Floor(sqRoot); // 8
double smaller = Math.Min(x, floored); // -80

Operator Shortcuts

C# offers several shortcuts for condensing simple operations.

The addition (+) and subtraction (-) operators can be doubled to form the increment (++) and decrement (--) operators. ++ increases a variable’s value by 1, and -- lowers it by 1.

+, -, *, /, and % can all be combined with the equals sign (=) to form compound assignment operators, such as +=, the compound addition operator. These operators take a variable to the left and a value to the right, perform the specified arithmetic operation, and assign the result back into the variable.

int a = 0;


a++;    // a = 1
a += 1; // a = 2
a *= 7; // a = 14
a--;    // a = 13
a %= 7; // a = 6
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