Tommy's Air Raid

You are the commander of an air defense network facing an attack by enemy bombers. Because of the presence of certain geographical features in the area they always attack from left to right on your screen. The enemy has some fighter jets also, which can fly across the screen in either direction.
You initially have 40 gun batteries, with the active one highlighted on the screen. To switch batteries, move the left and right arrow keys located on the numeric key pad.
Your batteries have a pop up/down feature to protect them from enemy bombs. When you hit the down arrow key, the active battery pops down under ground, lowering its probability of destruction if hit by a bomb. To pop it back up so that it can fire, hit the up arrow key. The game continues until all of your gun batteries have been destroyed, or the active battery (the one with you in it) has been destroyed.

What is abandonware ?