Cary Slack, age 12, of Sophia, N.C., for his question:

WHO INVENTED THE FIRST GUN?

No one knows who invented the gun. Most historians agree, however, that the first guns were probably the cannonlike weapons used by Arabs in North Africa around 1250. These and other early guns were made up of iron or brass tubes with small holes at the closed end for igniting the explosive charge.

Guns are classed by size. Hand carried guns are called small arms and include pistols, rifles and shotguns. Automatic weapons that can fire from 400 to 1,600 rounds of ammunition per minute are called machine guns. It's called a cannon or artillery when it is stationary or mounted on wheels or self propelled carriers.

Gun size is recorded in terms of caliber, which is measured in inches, hundredths of an inch or in millimeters or centimeters.