[C language - zero foundation _ study _ review _ lesson 4] data types and operations

Data types and their operations

Practice every day ：Int Can I provide a user identifier ？

Catalog

Data types and their operations

Constant ：

Variable ：

Integer data ：

integer constants ： That is, the integer in mathematics

Integer variables ：

Real data ：

Real constant ：

Real variable ：

Character data

character constants ：

String variable ：

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There are also different types in life , For example, people 、 animal 、 Plants represent their own attributes , In the computer is no exception . stay C Data types in language include basic data types and non basic data types , Common data types include integers 、 Real type 、 Character .

Constant ：

An immutable quantity in a high-level language program . for instance ： Is your ID number unchanged from your birth? . So it's a constant .

Variable ：

In high-level language programs , Amount that can be changed . Example ： You want to eat staple food now , It can be rice 、 Steamed bread is the amount that can be changed , Become variable .

Integer data ：

integer constants ： That is, the integer in mathematics

octal 、 Decimal system 、 Hexadecimal

stay C In the language, we define constants without leading, and the default is decimal .012 Indicates that the octal number is preceded by 0,0xAC Indicates that the input is a hexadecimal number, and the leading is 0x perhaps o( o )x.

main() {
	int a = 12;// Decimal system 
	int b = 045;// octal 
	int c = 0xAA;// Hexadecimal 
	printf("%d,%d,%d\n",a,b,c);// Three decimal number output 
}

Integer variables ：

Int Become a basic heading , Of the regular compilers 4 Bytes

short Short ： Occupy 2 Bytes

long Long integer ： Occupy 4 Bytes

unsigned No sign ( Later, say )

We can understand variables in this way , It's equivalent to a container for storing things , In real life, we go shopping. If there are few things, we take a small shopping cart , If there are many things, take a relatively large shopping cart, which can be compared to int、long. The more bytes it occupies, the more things it can store .

C Integer constants in the language do not include binary constants

Real data ：

Real data is what we call decimal in mathematics .

Real constant ：

Decimal point format ： By digital , The sign , The decimal point consists of .

example ：-0.1,1.5,1.

The rules of composition ： There must be a decimal point , At least one side of the decimal point consists of numbers , This is a bit strange , In our understanding, the decimal point should have data on both sides , But in C This is not the case in languages, such as ：.5

That is to say 0.5,1. Namely 1.0. You must remember this . In the future, you can't understand what it says .

Exponential form ：E And constitute the scientific counting method we have learned

for example ：1.2e3 5.2e10

The rules of composition ：E Both sides should be composed of arrays , The exponential part must be an integer （E The right side of is an integer ）

Real variable ：

Single precision ：float Occupy 4 Bytes are reserved after the decimal point 8 position

Double precision ：double Occupy 8 Bytes are reserved after the decimal point 16 position

float=1.12345678

double=1.12345678

Automatic data type conversion ： The highest precision bit of mixed data of different types .

explain ： We went to the supermarket to buy vegetables. We just started to take a small bag to hold things , Then take a big bag and put the small belt into the big bag , Whether there is space left for rotation is the rest of the big bag .

float d= 1.12345678;
	double e= 1.123456789101110113;
	printf("%f\n", d);
	printf("%f\n", e);//%f The decimal point is reserved by default 6 position , Inadequate supplement 0, More than rounding 

Character data

character constants ：

‘a’ ‘b’ ‘c’ Enclosed in single quotation marks , Only one byte can be stored . Cannot store Chinese characters , A Chinese character takes up two bytes .

Escape character ：

Escape character	significance	ASCII Code value （ Decimal system ）
\a	Ring the bell (BEL)	007
\b	Backspace (BS) , Move the current position to the previous column	008
\f	Change the page (FF), Move the current position to the beginning of the next page	012
\n	Line break (LF) , Moves the current position to the beginning of the next line	010
\r	enter (CR) , Move the current position to the beginning of the line	013
\t	Horizontal TAB (HT)	009
\v	Vertical tabulation (VT)	011
\'	Single quotation marks	039
\"	Double quotes	034
\\	The backslash	092

Escape characters occupy one byte

\ddd：1-3 Octal representation of 1 Characters

example ：’\101’ ‘\120’

\xhh: 1-2 A bit hexadecimal means 1 Characters

example ：‘\xA‘ ‘\xAB’

String constant ：

“abcde”

‘a‘ A character takes up a byte

“a” The string takes two bytes , because a Back by \0 We can't see .

String variable ：

 char a=‘b’;  

 char Equivalent to a container can only store one character .