How to trace this code?? and why they use thsi code?

Question

i need your help to trace this code . i have no idea how to do this

Answer 1

Which code?

Answer 2

for ( 1 : 2 ; i < 100 ; it t ) {
for ( j = 2 j j = = ( 1 / 3 ) ; j + + )
IF ( ! (ij ) ) break; / i f factor found, not prime
iF ( j> (i/j) ) cout << i <<" is prime \n"
}
return o;