'A' is a single char, one byte holding the ASCII value 65. "A" is a string literal, a two-byte array of char: 'A' followed by a null terminator '\0'. They're not interchangeable. char c = 'A' works; char c = "A" is a type error because you'd be assigning a pointer-to-array to a single byte. This trips up beginners because the printed representation is identical, but the underlying types differ. The general rule: single quotes for one character, double quotes for text strings (even single-character ones).
Programming Fundamentals · Interview question
What's the difference between 'A' and "A"?
A strong answer
What a weak answer sounds like
You know the answer. Do you know what gets you dinged?
Pro breaks down the answer most candidates actually give to this question — and the specific reason an interviewer marks it down. It’s the difference between sounding correct and sounding senior, on all 472 questions.
From the lesson
Arrays & Strings
A contiguous block of same-type values. How arrays work in memory, why indexing starts at 0, and the null-terminated convention that defines C-strings.