However, we can make some reasonable assumptions based on the information provided in the story:
* English: Charlie is living in New York City and interacts with everyone in English. He can read and write English, albeit with difficulties before his surgery.
* Possibly other languages: The story doesn't mention his background or family history, so it's possible he may have spoken another language at home.
It's important to remember that the story's focus is on Charlie's intellectual development, not his linguistic abilities. The author, Daniel Keyes, likely chose to focus on the challenges of language acquisition and comprehension, not on the nuances of specific languages.