how would i go about determining the big o, theta, and omega of a piece of code?

i know assigning i = 0, j = 0, y = 0 is the constant 3 and becomes insignificant to big o. is while( i < 6 ) 6x? do i multiply everything in the loop by 6x?

Code:void asdf() { int i = 0, j = 0, y = 0; while( i < 6 ) { j = 0; while( j < 5 ) { y = x = j; y = x ^ y + i; printf("x = %d y = %d\n", x,y); j += 2; } ++i; } }