C language - data type

C Why does language specify data types ？
What is data type ？
Like in real life ,6 It's an integer ,6.6 It's a decimal ,a It's a letter .
This whole number , decimal , Letters describe a data , That is to say, this is the type of data , That's the data type .
stay C In language , We will write the code , There will also be data in the code , So in C How to describe data in language , There are also data types , stay C In language , We abstract data types from real life , We abstract integers into integers , Abstract decimals into floating point , Abstract letters into characters .
meanwhile , We subdivide the data types of integer and floating point , Divide integers into short integers , integer , Long integer , long long ; Floating point type is divided into single precision floating point type and double precision floating point type .
Why do data types have sizes ？
We write code in the compiler , Save it , Put it in memory , Memory is common to all things in a computer , Memory is like a computer warehouse , As a warehouse for storing computer things .
Let's write down a data , Data in computer , So we have to store it in the warehouse , Data should take up space , Therefore, it specifies how much space the data types describing data occupy in memory , There should be restrictions on everything stored in the warehouse , You can't deposit it casually .
Compare memory to a village warehouse , Villagers should store things inside , It should be stipulated , Such as storing grain , Can only occupy 1 Square meters of space , Etc., etc. .. There should be clear restrictions .
So an integer number can occupy in memory 4 Bytes of space .
A character type number can be used in memory 1 Bytes of space .
A short integer number can occupy in memory 2 Bytes of space
An integer number can occupy in memory 4 Bytes of space
A long integer number can occupy in memory 4 Bytes of space
A long integer number can be used in memory 8 Bytes of space
It is easy to understand that bytes are compared to rectangles , It is easy to understand that bits are compared to small lattices
A byte =8 A bit .
One binary number can be stored in one bit .
That is, a rectangle =8 A little lattice .
in other words , The space occupied by an integer number in memory can be stored 32 Bit binary number ,
So the maximum number that an integer number can represent is 2 Of 32 Bit binary number
Because integer , Character , Wait, these data types are the representatives of numbers .
They occupy different spaces in memory , So it can represent numbers of different sizes .
So use appropriate types to represent different numbers , It can save memory space .
Different types occupy different sizes of space , The size of the number that can be expressed is different , When storing data , Use appropriate data types , Space utilization will increase .
How to use data types ？
Enter... In the compiler 20,20 To store in memory , The data type used will be 20 To apply for space , Because the data type is qualified to apply , Because in C Language specifies that data types take up space , because C Language specifies how much space can be used for each data type . Why is the data type specified , Instead of the specified number ？ Because the data type represents numbers , Is the representative of data , It describes numbers .
How data types are used ？
Data types are used to define variables , Define how much space the variable needs to request from memory , To store values . because C The language specifies how much space different data types can occupy , So when creating variables , Use data types to tell the compiler what it needs int Type space .
Let's say ： Compare the data type to the type of room , Variables are compared to rooms , Worth comparing to guests , If you do not specify the type of room , Don't tell the guest how big the room is , What kind of , How do guests check in ？