Currently Computer The most widely used character set and its encoding are USA American Standard Code for information interchange, American Standard Information It has been set as an international standard by the International Organization for Standardization (ISO), known as the ISO 646 standard. It is applicable to all Latin characters, including 7-digit ASCII code and 8-digit ASCII code.
ASCII Code uses a combination of the specified 7-bit or 8-bit binary numbers to represent 128 or 256 possible characters. The standard ASCII code is also known as the basic ASCII code. It uses 7-bit binary numbers to indicate all uppercase and lowercase letters, numbers 0 to 9, and punctuation marks, and special control characters used in American English.
Because the number of one-bit binary data can be expressed as (21 =) two states: 0 and 1, while the number of two-bit binary data can be expressed as (22) = four states: 00 , 01 , 10, 11, and so on. A 7-bit binary number can represent (27 =) 128 States. Each State is uniquely encoded as a 7-bit binary code, corresponds to one character (or control code), which can be arranged into a decimal number ranging from 0 ~ 127. Therefore, the 7-bit ASCII code is encoded using the seven-bit binary number, which can represent 128 characters.
0th ~ 32 and 127th (34 in total) are control characters or communication special characters, such as control characters: LF (line feed), Cr (Press ENTER), FF (page feed), del (delete), BEL (zhenling); Communication special characters: Soh (Text header), EOT (Text tail), Ack (confirmation), etc;
33rd ~ 126 (94 in total) is a character, of which 48th ~ Number 57 is 0 ~ 9. 10 Arabic numerals; 65 ~ The 90 is 26 uppercase English letters, 97 ~ 26 lowercase English letters (122) And some punctuation marks and operator numbers.
Note: In the storage unit of a computer Standard ASCII Value Occupies one byte (eight binary bits), and the highest bit (B7) is used as the parity bit. The so-called parity refers Code A method used to check whether an error occurs during transmission. Generally, there are two methods: Odd checksum and even verification. Odd check rules: correct code must contain an odd number of 1 bytes. If the number is not an odd number, 1 is added to the highest bit of B7. The parity check rules are as follows: correct code: the number of 1 in a byte must be an even number. If the number is not an even number, 1 is added to the highest bit of B7.
128th ~ 255 is an extended character (not commonly used ), The expanded ASCII code allows 8th characters of each character to be used to determine the additional 128 special characters, foreign letters, and graphical symbols .
For ease of query, the ASCII code table is listed below (note that ASCII is binary instead of decimal, and the following table is in decimal format only for understanding ): |
