A software delay might be implemented as a for or while loop like for example:

i = 10000;  /* A software delay */
do i‑‑;
while (i != 0);

Such software delays will keep the CPU busy with executing instructions performing nothing except to make the time go by. Time delays are much better implemented using a hardware timer. The timer interrupt is set up and after that, the CPU goes down into a low power mode until it is awakened by the interrupt.