At the beginning of the story, Charlie is very shy, passive, and eager to please. He feels inferior to others because of his low IQ and inability to learn and understand things quickly. He is often made fun of and mistreated by his coworkers at the factory where he works. Despite his disabilities, Charlie is a kind and compassionate person who is always willing to help others.
After the experimental surgery, Charlie's intelligence increases significantly. He becomes extremely curious and knowledgeable, and his personality becomes more assertive and independent. He begins to question his surroundings and the people in his life, and he becomes aware of the injustices and discrimination that he has faced. As his intelligence grows, Charlie develops a sense of self-worth and a desire to experience all that life has to offer.
However, as his intelligence continues to increase, Charlie also experiences emotional and psychological challenges. He becomes frustrated and angry at the way he has been treated in the past and begins to feel isolated from his friends and colleagues. He also struggles to cope with the ethical implications of the experiment and the knowledge that his enhanced intelligence is temporary.
Overall, Charlie's personality undergoes a profound transformation throughout the novel. He emerges as a complex and dynamic character who exhibits a wide range of emotions and experiences as his intelligence develops and declines.