There are 6 major character types in Final Fantasy 1. What is listed below are their strengths and abilties before their class change, and then after.

He is a trained warrior that can use just about any weapon and is able to wear heavy armor. He can attack very fast. When he transforms into the knight, he is able to gain some white magic spells, but only up to third level

Agility and dexterity are the strong points of this character. The thief is good to have when you need to avoid an attack from an enemy. When he becomes the ninja, he is able to use some black magic, but only up to fourth level.

A master of martial arts. He is physically and mentally tough. He is able to fight with a select group of weapons, but when he is totally bare handed, he really deals out the damage. When he becomes a grand master, this damage only becomes more deadly.

The red mage has the ability to learn some of both white magic and black magic. He can also use some weapons pretty decently. When he becomes a red wizard, his spell capacity is increased.

Known to most people that play role-playing games, both computer and table top, the white mage can also be called a cleric. She is able to heal characters quite effectively as well as cast spells that are devastating to undead. When she becomes a white wizard, she is able to gain a few more spells

The true powerhouse of the magic realm, the black mage has the ability to control the elements. He commands fiery infernos, lightning storms, and blizzards with sheer gestures and spoken words. Now that's power. When he becomes a black wizard, he just kicks even more butt, especially with my favorite spell, Nuke.