The information exchange code currently commonly used in the Spanish field is ASCII code. ASCII code, also known as 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. ASCII code uses a specified combination of 7- or 8-bit binary numbers to represent 128 or 256 possible characters, which can represent all uppercase and lowercase letters, numbers 0 to 9, punctuation marks, and special control characters used in American English. .
The operating environment of this tutorial: Windows 7 system, Dell G3 computer.
The Western character encoding widely used in computers is the American Standard Information Interchange Code, whose English abbreviation is ASCII.
ASCII (American Standard Code for Information Interchange, American Standard Code for Information Interchange): It 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 was last updated in 1986. So far, a total of 128 characters have been defined.
The reason for ASCII
In computers, all data must be represented by binary numbers when storing and operating (because computers use high and low levels (representing 1 and 0 respectively), for example, 52 letters (including uppercase letters) like a, b, c, d, numbers such as 0 and 1, and some commonly used symbols (such as *, #, @, etc.) in computers Binary numbers must also be used when storing. As for which binary numbers are used to represent which symbols, of course everyone can agree on their own set (this is called encoding). If everyone wants to communicate with each other without causing confusion, then Everyone must use the same encoding rules, so the relevant standardization organizations in the United States introduced ASCII encoding, which uniformly stipulates which binary numbers are used to represent the above common symbols.
The American Standard Code for Information Interchange was developed by the American National Standard Institute (ANSI) and is a standard single-byte character encoding scheme for text-based data. It was originally an American national standard and was used as a common Western character encoding standard for different computers to communicate with each other. Later, it was established as an international standard by the International Organization for Standardization (ISO), called the ISO 646 standard. Applies to all Latin script letters.
ASCII expression
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)
Such as control characters: LF (line feed), CR (carriage return), FF (page feed), DEL (delete), BS (backspace), BEL (ring), etc.;
Special characters for communication: SOH (head of text), EOT (end of text), ACK (confirmation), etc.;
ASCII values of 8, 9, 10 and 13 are converted to backspace, tab, line feed and Enter character. 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 [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 an additional 128 special symbol characters, foreign letters, and graphic symbols.
Extended knowledge: size rules
The size rules of common ASCII codes: numbers < uppercase letters < lowercase letters.
1. Numbers are smaller than letters. Such as "7" < "F";
2. The number 0 is smaller than the number 9, and increases in sequence from 0 to 9. Such as "3"<"8" ;
3. The letter A is smaller than the letter Z, and increases in order from A to Z. Such as "A"<"Z" ;
4. The uppercase letters of the same letter are 32 smaller than the lowercase letters. Such as "A"<"a".
The ASCII code sizes of several common letters: "A" is 65; "a" is 97; "0" is 48
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