Question 1: What are special characters? Those that conflict with some tags on the web page.

Question 2: Which characters are "special characters". Special characters refer to traditional or commonly used characters. In addition to symbols, there are symbols that are less frequently used and difficult to input directly, such as mathematical symbols; unit symbols; tab characters, etc.

For example: *,◎℃,a, à, à, á, á, ?, a, ?, ?, ?, ?, ?, ?. e, è, è, é, é, ê, ê, ?, ?. i,&,#,

and so on.

Identifier--(Uniform Resource Identifier, referred to as URI) is a protocol of the Internet Element through which you can locate any remote or local available resource (these resources usually include HTML documents, images, video clips, programs, etc.).

Question 3: What are special characters? An identifier (IDentifier) ??refers to a symbol used to identify an entity. It has different meanings in different application environments. In daily life, identifiers are used to specify something or a person, and his or her name is used; when solving equations in mathematics, we often use variable names or function names of one kind or another; In programming languages ??

Question 4: What are special characters that conflict with some tags on the web page?

Question 5: What are special characters that are difficult to print?

Question 6: What are the following special characters? The password is 6-18 characters. The combination of letters, numbers and special symbols means that the password must contain at least 6 characters and a maximum of 18 characters. , the password needs to contain numbers, letters and punctuation marks

Question 7: What does it mean that special characters cannot appear when filling in information? Only uppercase and lowercase letters and numbers can be used

Question 8: Email name What special characters cannot be included? Email names generally consist of numbers and English letters.

Special characters generally refer to characters that are not easy to print.

1. Non-normal characters are special characters;

2. Characters that cannot be input directly from the keyboard are special characters;

3. You Characters that are not allowed by the object to be used are special characters;

For example:

*,◎℃,a, à, à, á, á, ?, a, ?, ?, ?, ?, ?, ?. e, è, è, é, é, ê, ê, ?, ?. i,&,#,

3.1 Common characters

Consists of all those printing and non-printing characters that are not explicitly designated as metacharacters. This includes all uppercase and lowercase alphabetic characters, all numbers, all punctuation, and some symbols.

3.2 Non-printing characters Character Meaning

\cx matches the control character specified by x. For example, \cM matches a Control-M or carriage return character. The value of x must be one of A-Z or a-z. Otherwise, c is treated as a literal 'c' character.

\f matches a form feed character. Equivalent to \x0c and \cL.

\n matches a newline character. Equivalent to \ and \cJ.

\r matches a carriage return character. Equivalent to \x0d and \cM.

\s matches any whitespace character, including spaces, tabs, form feeds, etc. Equivalent to [ \f\n\r\t\v].

\S matches any non-whitespace character. Equivalent to [^ \f\n\r\t\v].

\t matches a tab character. Equivalent to \x09 and \cI.

\v matches a vertical tab character. Equivalent to \x0b and \cK.

3.3 Special characters

The so-called special characters are characters with special meanings, such as the * in *.txt mentioned above. Simply put, they mean the meaning of any string. . If you want to find files with * in the file name, you need to escape the *, that is, add a \ before it. ls\*.txt. Regular expressions have the following special characters.

Question 9: What does it mean if the name of the credit card application contains special characters? What special characters