Why do I need to have my functions written first in my PowerShell script?

Question

I have a script that I am utilizing functions to wrap parts of the code that allow me to move through the sections at a specified point. What I have found is that I have to

Answer 1

A solution from Microsoft blog, Enclose the main code in a block and call in the end,

$MainFunction={
   $stepChoice = read-host 'Where would you like to start.'
   switch($stepChoice)
   {
       1{Step1}
       2{Step2}
       3{Step3}
   }
}
# Steps.ps1 
function Step1 { 
  'Step 1' 
   Step2 
} 
function Step2 { 
  'Step 2' 
   Step3 
} 
function Step3 { 
  'Step 3' 
  'Done!' 
}
#This line executes the program
& $MainFunction