1. The system first converts all floating-point numbers into double-precision operations, and intercepts the first seven digits of the final result as significant digits, which can make the calculation result more accurate.

2. Effective digit: from the first digit on the left that is not 0 to the exact digit, all digits are called effective digits of this digit. For example, the valid numbers of 1.24 are 1, 2 and 4. The valid numbers of 0.24 are 2 and 4.

3. For the same binary number, if a signed type is defined, the first digit represents a sign, 0 represents a positive number, and 1 represents a negative number; If unsigned is defined, the first bit is the value.

4. If expressed by exponent, the effective digits of floating-point type are 6~7 digits. Double type is 15~ 16 digits, which is related to numbers.

5. Where did you read it? Don't!

Integer constants are divided into decimal, octal and hexadecimal:

The octal form is 0 12 with zero in front, and the hexadecimal form is 0x 12 with 0x in front (note that X is preceded by zero).

Adding \ before the octal number indicates that it is a character constant. For example, \0 12 is a character with ASCII code 10!

I typed this word for word, I hope everyone will adopt it!