I was wondering why bitcoin uses   Sha256(Sha256()) instead of sha256() . Is it because the hashing algorithm is not considered safe?


If I ran the below program on a computer with near infinite computing power what value of C would the loop terminate? 

y = "abc"
C = 0
y = sha256(y)
y = sha256(y)

do loop until y = sha256("abc")
   {
    y = sha256(y)
    C = C + 1
   }
   
Print c