Not octal. . . Everything in the computer is binary. . . 65 will also be stored in binary, that is, 0 10000 1, that is, 8 bits, that is, a byte, which means that A in your char a is 0 100 000 1.

The format of the output depends on the printf statement.

If so

printf("%d "，a)； //Output integer 65

printf("%c "，a)； //output character a

printf("%o "，a)； //Output octal 0 10 1

printf("%x "，a)； //output hexadecimal 0x4 1

Although the output formats are different, they are all binary 0 10000 1.