What is a character constant What is the difference between a character constant and a string consta

Valid character constants are:

a.'084' is not legal, there is no 8 in octal.

b.'x43' legitimate.

c.'ab' is not valid and can only be one character.

d."0" is not valid and the string does not need to write a terminator.

Invalid character constants are.

a． ‘n’b． ‘101’c． ‘xy’d． ‘t’

a． ‘n’

b． ‘101’

d． ‘t’

A character constant is a character enclosed in a single parentheses.

There are two ways to represent it:

One is to use the graphic symbol of the character, such as'b' ，'y'，'*'。

In addition, it can also be represented by the ASCII code of the character, that is, it starts with a backslash ( ) followed by the ASCII code of the character, this method is also known as escape sequence notation, and the specific method is: there are two forms:

One is the octal ASCII code of the character, which is represented as: DDD Here, DDD is the octal value.

Another uses a hexadecimal ASCII code value of the character, denoted as XHH where HH is a two-digit hexadecimal value.

Such as:'a' ，'\101'with'x41'All represent the same character constant.

Escape sequence notation can also be used to represent some special characters, to display special symbols, or to control the output format.

Here are the commonly used special escape characters. Please see**.

Note: Special escape characters must be lowercase letters.

Character constants. In the Pascal language, a character constant is made up of a single character, all of which are derived from the ASCII character set, for a total of 256 characters. In a program, a single character is usually enclosed in a pair of single quotation marks to represent a character constant.

Such as:'a'，'a'，'0'Wait. In particular, for single-quoted characters, it is denoted as''''。

For ASCII character sets, each character is numbered 0 255 by its position in the character set, and the number is called the ordinal number of the corresponding character.

To put it simply: a character represents a constant, or a character implied quantity. For example, "pie" =

1. Different forms:

Character constants are single quotes.

caused by a character; String.

A constant is a number of characters caused by double quotation marks.

2. The meaning is different

A character constant is equivalent to an integer.

value, which can participate in the expression.

of operations; A string constant represents an address value (where the string is stored in memory). Character constants can be assigned to character variables, such as:"char b='a';", but you can't assign a string constant to a character variable, and you can't assign a value to a string constant.

3. Occupy different memory:

The character constant occupies only one byte; String constants are several bytes (at least one character ending flag). Not taking up any storage space is part of the directive and is not changed after compilation. A string constant is a sequence of characters enclosed in double quotation marks.

There are two types of character constants:

One is a normal character, which is a character enclosed in a single apostrophe, such as'b' ，'y'，‘？Character constants, when stored in a computer's storage unit, are stored in their ** (usually ASCII**).

The other is an escape character.

That is, special character constants. A transfer character is a special form of representation of a character in the C language, which means to convert the character after the backslash into another meaning.

They differ in data type and data length. Specifically, the length of the character constant generally does not exceed 1, and the data type is char. The data type of a string constant is string or char*, and its length is often greater than 1.

Characters and strings are two completely different types of things, a character represents a letter, and a string represents a collection of many characters.

A string constant is a string of characters, such as ancd, and a character constant is a single character, such as a.

Valid character constants are:

a.'084' is not legal, there is no 8 in octal.

b.'x43' legitimate.

c.'ab' is not valid and can only be one character.

d."0" is not valid and the string does not need to write a terminator.

Invalid character constants are.

a． ‘n’b． ‘101’c． ‘xy’d． ‘t’

a． ‘n’

b． ‘101’

d． ‘t’

Select ca has double quotation marks and is a string.

b Only one character in a single quotation mark can be used.

d 0 indicates that it is occimal, and only numbers from 0 to 7 can appear.

e The writing is incomplete, and the single quotation mark on the right half is missing.

The formal symbol in the mind is just one of his formats.

A character enclosed in a single apostrophe is a character constant. For example, 'a', ' ', 'd' are valid character constants that occupy one byte in memory. Note:

1. Sun Chun's character constant only includes one character, such as 'ab' is not legal.

2. Character constants distinguish between uppercase and lowercase letters, such as 'a' and 'a' are two different character constants.

3. The apostrophe (') is a delimiter, not part of the character constant.

The so-called character constant is a character enclosed in English single quotation marks. When using character constants, you should be aware of:

1. The uppercase and lowercase characters in single quotation marks represent different character constants, for example, 'y' and 'y' are two different character constants.

2. Character constants can only be enclosed in single quotation marks in English, and cannot be enclosed in double quotation marks. For example, "y" is not a character norm, but a string.

3. If there is a space in a single quotation mark, it is also a character constant.

4. A single quotation mark can only contain 1 character, and the writing of 'xyz' is wrong. However, if there is more than 1 character, the first one except the last one will be automatically invalidated, which should be avoided in programming use.

The above content refers to: Encyclopedia - Character Constants.