What is the difference between 65 and the letter A in binary?

Question

What is the difference between 65 and the letter A in binary as both represent same bit level information?

Answer 1

Basically, a computer only understand numbers, and not every numbers: it only understand binary represented numbers, ie. which can be represented using only two different states (for example, 1 and 2, 0V and 5V, open and close, true or false, etc.).

Unfortunately, we poor humans doesn't really like reading zeros and ones... So, we have created some codes, to use number like if they were characters: one of them is called ASCII (American Standard Code for Information Interchange), but there is also some others, such as Unicode. The principle is simple: all the program have to do is manipulating numbers, what any CPU does very well, but, when it comes to displaying these data, the display represent them as real characters, such as 'A', '4', '@', or even a space or a newline.

Now, as soon as you are using ASCII, the number 65 will represent the letter 'A'. All is a question of representation: for example, the binary number 0bOOOO1111, the hexadecimal one 0x0F, the octal one 017 and the decimal number 15 all represent the same number. It's the same for letter 'A': think of ASCII as a base, but instead of using the base 2 (binary), 8(octal), 10(decimal) or 16(hexadecimal), to display numbers, it's used in a complete different manner.

To answer your question: ASCII 'A' is hexadecimal 0x41 is decimal 65 is octal 0101 is binary 0b01000001.