Literals

Integer Literals

decimal; octal; hexadecimal

• begin with 0 (zero) are interpreted as octal
• begin with either 0x or 0X are interpreted as hexadecimal

int k;
 
scanf("%x", &k);		// cin >> F
printf("%d", k);		// cout << 15

[! Attention]

• The value of a decimal literal is never a negative number. The minus sign is not part of the literal. ==The minus sign is an 🔗^4ded86 that negates the value== of its (literal) operand.

• By default, decimal literals are signed
  whereas octal and hexadecimal literals can be either signed or unsigned types.

• There are no literals of type short

Floating-point Literals

either a decimal point or an exponent specified using scientific notation.

Attention

By default, floating-point literals have type double. We can override the default using a suffix. ==So, double is preferable.==

Character and Character String Literals

The type of a string literal is array of constant chars.

在 C/C++ 中，“” 会被解释为以 \0 结束，吗？

Boolean and Pointer Literals

The words true and false are literals of type bool

The word nullptr is a pointer literal.

Escape Sequences

• \x followed by one or more hexadecimal digits
• \ followed by one, two, or three octal digits
  • Note that if a \ is followed by more than three octal digits, only the first three are associated with the \.

Specifying the Type of a Literal

using some letters as prefix or suffix. (C++ Primer, p.40, Table2.2)