Integer: the representation of integer data: decimal, octal, and hexadecimal integer data has the following reserved words: int, short, long, signed, unsigned integer data including signed) unsigned integer values of two types of integer data types: short: 2 bytes INT: 2 or 4 bytes (determined by the compiler, is a 16-bit compiler with 2 bytes and a 32-bit compiler with 4 bytes) LONG: 4 bytes unsigned and signed reserved words are applicable to the combination of the above three reserved words, it is used to determine whether an integer variable is a signed integer variable. At the same time, signed reserved words can be omitted.
| |
Signed |
Unsigned |
| Short |
-32768 ~ 32767 |
0 ~ 65535 |
| Int |
-32768 ~ 32767-2147483648 ~ 2147483647 |
0 ~ 655350 ~ 4294967295 |
| Long |
-2147483648 ~ 2147483647 |
0 ~ 4294967295 |
Output representation of Integer constants: For details, refer to the printf function.
| Decimal |
Octal |
Hexadecimal |
| |
Start with 0 |
Starting with 0x and 0x |
| |
|
L, l end |
| % D |
% O (vomit) |
% X lowercase letters output % x uppercase letters output |
| |
% # O: Output prefix 0 |
% # X output prefix 0x % # x output prefix 0x |
| % UD unsigned count |
% UO |
% Ul |
We declare an integer constant. during compilation, the C compiler will automatically allocate it to one of short, Int, and long according to the constant size. Float: float: indicates a single float type in four bytes. The value range is 3.4 * 10-38e ~ 3.4*10 + 38 edouble: Double Floating Point type, expressed in 8 bytes, range: 1.7 * 10-308e ~ 1.7*10 + 308e floating point numbers are signed and do not have any unsigned floating point numbers. The floating-point constant is only in decimal format. All floating-point constants are double type by default. If the floating-point number is smaller than 1, the first 0 can be omitted. It can be divided into signed and unsigned char (-128 ~ 127), unsigned char (0 ~ 255); occupies a byte here, we need to mainly different compilers for the char type of data into integer processing difference, for Chinese characters, we need to define as unsigned char type. When defining a string array, char STR [N] can actually store n-1 valid characters. The Compiler automatically adds the "/0" null character. Character constant: it can contain single quotes or ASCII values. For characters that cannot be expressed by keyboard symbols, it is expressed by '/' or '/ASCII code value. For more information, see related documents. Double quotation marks ("") are used to enclose character array constants, also called string constants. Pointer type: used to store declared variable addresses. Different types of variables can be integer, floating point, structured, and combined pointers. Valueless: The Void byte length is used to explicitly indicate that a function does not return any value. Second, a pointer of the same type is generated.
