What is the main difference between the 'while' and 'until' loops?

The main difference between while and until loops lies in their condition evaluation:

• while loop: Executes the block of code as long as the specified condition is true. If the condition is false at the start, the loop body will not execute at all.

  // Example in Go
  i := 0
  for i < 5 {
      fmt.Println(i)
      i++
  }

• until loop: Executes the block of code until the specified condition becomes true. This means the loop continues as long as the condition is false.

  // Example in Ruby
  i = 0
  until i == 5 do
      puts i
      i += 1
  end

In summary, a while loop checks the condition before executing the loop body, while an until loop checks the condition after executing the loop body.