ontent
“w” → write mode (creates file if not exist).

File.read → reads entire file content.

Output in console:

Hello Ruby File!
And file test.txt is created with that text.

Block

3.times { puts “Ruby is fun!” }

Proc

say_hello = Proc.new { |name| puts “Hello, #{name}” }
say_hello.call(“Sara”)

Lambda

square = -> (x) { x * x }
puts square.call(5)
Block → Small piece of code in {} or do…end.

Proc → Stored block that can be reused.

Lambda → Like Proc but stricter with arguments.

Output:

Ruby is fun!
Ruby is fun!
Ruby is fun!
Hello, Sara
25

class Person
attr_accessor :name, :age # creates getter & setter

def initialize(name, age) # constructor
@name = name
@age = age
end

def introduce
“Hi, I’m #{@name} and I’m #{@age} years old.”
end
end

p1 = Person.new(“Ali”, 25)
puts p1.introduce
class defines a blueprint.

@name and @age are instance variables.

initialize runs when object is created.
Output:

Hi, I’m Ali and I’m 25 years old.

def greet(name)
return “Hello, #{name}!”
end

puts greet(“Ayesha”)
def starts a method, end closes it.

return gives back a value.
Output:

Hello, Ayesha!

While Loop

i = 1
while i <= 5
  puts i
  i += 1
end

• Runs while condition is true.
  Output:

1
2
3
4
5

For Loop

for n in 1..5
  puts n
end

• 1..5 means range from 1 to 5.
  Output: 1 2 3 4 5

Each Loop

[1, 2, 3, 4, 5].each do |num|
  puts num * 2
end

• Iterates over each element.
  Output:

2
4
6
8
10

age = 18

if age >= 18
puts “You are an adult.”
elsif age >= 13
puts “You are a teenager.”
else
puts “You are a child.”
end
if … elsif … else … end is used for decision making.
Output:

You are an adult.

student = { “name” => “Ali”, “age” => 22, “grade” => “A” }
puts student[“name”] # Ali
student[“age”] = 23 # update
puts student.inspect
Hashes store key-value pairs.

Keys can be strings “name” or symbols :name.
Output:

Ali
{“name”=>”Ali”, “age”=>23, “grade”=>”A”}

fruits = [“apple”, “banana”, “cherry”]

puts fruits[0] # apple
puts fruits.length # 3
fruits << “mango” # Add new element
puts fruits.inspect # Show complete array
Arrays store multiple values.

Index starts from 0.

<< means “append”.

Output:

apple
3
[“apple”, “banana”, “cherry”, “mango”]

name = “Saim” # String
age = 25 # Integer
height = 5.9 # Float
is_student = true # Boolean

puts “Name: #{name}, Age: #{age}, Height: #{height}, Student: #{is_student}”
Ruby is dynamically typed → no need to mention string, int, etc.

{} → used inside strings for interpolation (inserting values).

Output:

Name: Saim, Age: 25, Height: 5.9, Student: true

puts “Hello, World!”
puts → Prints text with a new line at the end.

“Hello, World!” is a string.
Output:

Hello, World!