When dual-wielding, a character gets the regular number of attacks based on BAB, plus a single extra attack with the off-hand. Unless one has feats such as Improved Two-Weapon Fighting, etc., which increase the number of off-hand attacks.
For example, a Ftr11 dual-wielding a gnome hooked hammer would have three regular attacks (+11/+6/+1 BAB) and one off-hand attack. If he had the Improved Two-Weapon Fighting feat, he would get two off-hand attacks.