[c language] When statement conditional interpretation question.

while(parr - arr <= 9) 
{   
    sum += (*parr);    
    parr ++;   
} 
printf ("Mean of my test score: %d \n", sum/10);   
return 0; 

while(parr - arr <= 9) 
{   
    sum += (*parr);    
    parr ++;   
}