Enemy random movement [on hold]

i'm just new in here, in this web and i really have no idea about coding things. And now i just got assignment to create a game, a game that have 3 enemy with random movement, while each of them are not going to crash while they move around the arena (random). The player can hit the enemy, the enemy doesn't chase the player. Now...the problem is how to make the enemy move randomly? Need help guys, for my assignment score... Thanks! (Sorry if my english is wrong, english is not my native language) #note; array and struct cannot be used in this assignment, because the teacher said so...