##### 15.4.1.2 C and C`++` Constants

gdb allows you to express the constants of C and C`++` in the
following ways:

- Integer constants are a sequence of digits. Octal constants are
specified by a leading 0 (i.e. zero), and hexadecimal constants
by a leading 0x or 0X. Constants may also end with a letter
l, specifying that the constant should be treated as a
`long`

value. - Floating point constants are a sequence of digits, followed by a decimal
point, followed by a sequence of digits, and optionally followed by an
exponent. An exponent is of the form:
e[[+]|-]
`nnn`, where`nnn`is another sequence of digits. The + is optional for positive exponents. A floating-point constant may also end with a letter f or F, specifying that the constant should be treated as being of the`float`

(as opposed to the default`double`

) type; or with a letter l or L, which specifies a`long double`

constant. - Enumerated constants consist of enumerated identifiers, or their integral equivalents.
- Character constants are a single character surrounded by single quotes
(
`'`

), or a number—the ordinal value of the corresponding character (usually its ascii value). Within quotes, the single character may be represented by a letter or by escape sequences, which are of the form \`nnn`, where`nnn`is the octal representation of the character's ordinal value; or of the form \`x`, where`x`is a predefined special character—for example, \n for newline. - String constants are a sequence of character constants surrounded by
double quotes (
`"`

). Any valid character constant (as described above) may appear. Double quotes within the string must be preceded by a backslash, so for instance "a\"b'c" is a string of five characters. - Pointer constants are an integral value. You can also write pointers to constants using the C operator &.
- Array constants are comma-separated lists surrounded by braces { and }; for example, {1,2,3} is a three-element array of integers, {{1,2}, {3,4}, {5,6}} is a three-by-two array, and {&"hi", &"there", &"fred"} is a three-element array of pointers.