what does ascii code mean

The ascii code is a computer coding system based on the Latin alphabet; the ascii code is the abbreviation of "American Standard Code for Information Interchange". It is mainly used to display modern English and other Western European languages. It is the most common information exchange Standard, using specified combinations of 7- or 8-bit binary numbers to represent 128 or 256 possible characters.

The operating environment of this tutorial: Windows 10 system, DELL G3 computer.

What does ascii code mean

ASCII (American Standard Code for Information Interchange): The American Standard Code for Information Interchange is a computer coding system based on the Latin alphabet, mainly Used to display modern English and other Western European languages. It is the most common standard for information exchange and is equivalent to the international standard ISO/IEC 646. ASCII was first published as a standardized type in 1967, and the last update was in 1986. So far, a total of 128 characters have been defined

Expression method

ASCII code uses a specified 7-bit or 8-bit binary number combination to represent 128 or 256 possible characters. Standard ASCII code, also called basic ASCII code, uses 7 binary digits (the remaining 1 binary digit is 0) to represent all uppercase and lowercase letters, numbers 0 to 9, punctuation marks, and special controls used in American English. character . Among them:

0~31 and 127 (33 in total) are control characters or special communication characters (the rest are displayable characters)

For example, control characters: LF (line feed), CR (return) Car), FF (page feed), DEL (delete), BS (backspace), BEL (ring), etc.;

Special characters for communication: SOH (head of text), EOT (end of text), ACK (Confirm), etc.;

ASCII values ​​8, 9, 10 and 13 are converted into backspace, tab, line feed and carriage return characters respectively. They do not have a specific graphic display, but will have different effects on text display depending on the application.

32~126 (95 in total) are characters (32 is a space), of which 48~57 are ten Arabic numerals from 0 to 9.

65~90 are 26 uppercase English letters, 97~122 are 26 lowercase English letters, and the rest are some punctuation marks, arithmetic symbols, etc.

Also note that in standard ASCII, its highest bit (b7) is used as a parity bit. The so-called parity check refers to a method used to check whether errors occur during code transmission. It is generally divided into two types: odd check and even check. Odd parity rules: the number of 1's in a byte of the correct code must be an odd number. If it is not an odd number, add 1 to the highest bit b7; even parity rules: the number of 1's in a byte of the correct code must be an even number. , if it is not an even number, add 1 to the highest bit b7.

The last 128 are called extended ASCII codes. Many x86-based systems support the use of extended (or "high") ASCII. Extended ASCII allows the 8th bit of each character to be used to determine additional 128 special symbol characters, foreign language letters, and graphic symbols.

Size rules

Common ASCII code size rules: numbers

1. Numbers are smaller than letters. Such as "7"

2. The number 0 is smaller than the number 9, and increases in order from 0 to 9. Such as "3"

3. The letter A is smaller than the letter Z, and increases in order from A to Z. Such as "A"

4. The uppercase letters of the same letter are 32 smaller than the lowercase letters. Such as "A"

The ASCII code sizes of several common letters: "A" is 65; "a" is 97; "0" is 48

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