What does it mean when the first “for” parameter is blank?

Question

I have been looking through some code and I have seen several examples where the first element of a for cycle is omitted.

An example:

for ( ; hole*2          


        

Answer 1

That means loop control variable is initialized before the for loop .

For C  code,

int i=0;
for( ; i <10 ; i++) { } //since it does not allow variable declaration in loop 

For C++  code,

for(int i=0 ; i <10 ; i++) { }