Simplify the following text for a Grade 7 native English-speaking person.
Original: In modern terminology , SOS is a Morse `` procedural signal '' or `` prosign '' , and the formal way to write it is with a bar above the letters , i.e. SOS .
Simplified: In modern terminology , SOS is a `` procedural signal '' or `` prosign '' , and the formal way to write it is with a bar above the letters . It should be written SOS .