# Step 1: Define the original string
original_string = "Hello, world!"
# Step 2: Specify the character to be replaced
character_to_replace = 'o'
# Step 3: Specify the replacement character
replacement_character = 'X'
# Step 4: Use the gsub method to replace all occurrences of the specified character
result_string = original_string.gsub(character_to_replace, replacement_character)
# Step 5: Display the original and modified strings
puts "Original String: #{original_string}"
puts "Result String: #{result_string}"