Look at the definition first. A single character enclosed in single quotation marks or a string of characters enclosed in double quotation marks is a character constant.

c

& amp'

Is a single character enclosed in single quotation marks, correct.

a

\xff '

b

'\65'

d'\028 '

Are some characters enclosed in single quotation marks, but because they are preceded by

There is an escape character.

'\'

You can't say that they don't meet the definition, they are all illegal.

a

\xff '

middle

\x '

The combined representation is a hexadecimal number.

Familial benign hypercalcemia Familial Benign Hypercalcemia

=

10

binary

255

It represents the ascii of invisible characters.

Code,

legal

b

'\65'

In the same way; In a similar way

'\'

+

Three decimal digits

\ddd '

this means

Octal number. '\65'

=

'\065'

=

10

binary

53,

be

f '

American standard code for information interchange code

Code representation. single

Word, law.

d

'\028'

The same as above means octal number, but every eight octal numbers will enter one and will not appear.

eight

Yes, so the format is correct but the value is wrong. Illegal.