‘Je Suis Prest’ and ‘Je Suis Prêt’ both mean the same thing (I Am Ready), but Je Suis Prest is the original version!
A circumflex, or ‘hat’ above a French letter (î, â, ê) means there is a lost ‘s’, which existed in the original Latin version of the word but over the centuries, as the language evolved and changed, has been dropped.