Shulou(Shulou.com)06/01 Report--

This article Xiaobian for you to introduce in detail "c language enumeration type enum how to use", the content is detailed, the steps are clear, the details are handled properly, I hope this "c language enumeration type enum how to use" article can help you solve doubts, the following follow the editor's ideas slowly in-depth, together to learn new knowledge.

I. the concept of enumeration

My understanding of enumerations is to enumerate some fixed values and give them their own names, such as Ture for 1 and False for 0.

Both Ture and false represent the same type of data, for example, the right or wrong of logic.

We simulate the IE interrupt enable register of 51 single-chip microcomputer to give an example.

We can compare the data of the single-chip microcomputer register chip, when we set the value of the IE register equal to 0x01, it means to turn on the external interrupt 0 and allow all interrupts when it is set to 0x80.

These enumerated values are for the fixed values of the register IE, so we can call these values the same type of data, and we rename them to make them easy to read and remember, which is one of the important functions of enumerations.

Second, several uses of enumerations 1. Define enumerated values directly, and then assign values to ordinary variables.

The above code defines an enumerated type, but does not name the enumerated type.

There is no way to define enumerated variables like this kind of enumeration, but, uh, this can also be used.

We can also output the correct value by defining a normal variable and assigning the value of the enumeration to him. I often use this method lazily.

two。 Define enumerations with names

Here we define an enumeration named WeekDay, so we can define an enumerated variable named day through this enumeration type.

Define enumerated aliases

In this code, the alias of the enumeration is defined as WeekDay through typedef, and then we directly use WeekDay day to define an enum variable, which is the most frequently used method.

4. What is the use of enumeration and where is it used?

We have learned some of the definition methods of enumerations above, so what is the use of enumerations in the product?

The purpose of enumerations:

1. Name a fixed value as a subscript for array access. When there is a lot of fixed data, such as dozens or hundreds, it is difficult to remember what each value means if you should express it from 0 to 100.

For example, products that have done car troubleshooting before need to read Pid data and store them in an array, while PID has nearly 100.

If you were asked to write down which PID parameter each represents, you would probably collapse.

Isn't it convenient for me to enumerate each PID parameter to know the name of what parameter it is?

Because each PID is stored separately in an element of the array, I can quickly pull the specified PID parameter out of the array by using this name as the subscript.

I'm sure you can understand the difference between reading with enumeration and reading without enumeration.

two。 It can be used as a variable to flexibly allocate array size.

When we define an array, we directly use the last value of the enumerated type as the array size.

The next time you want to add or decrease the PID parameter, you don't have to change the size of the array, which is very convenient.

3. Enumeration as a setting value

The figure above shows the firmware library code for STM32, which configures the enumerated definition of the GPIO mode.

We can see that each enumerated value represents a pattern, and finally the mode configuration of GPIO is completed by writing these values into the corresponding register.

After reading this, the article "how to use the enumerated type enum in c language" has been introduced. If you want to master the knowledge points of this article, you still need to practice and use it yourself. If you want to know more about related articles, welcome to follow the industry information channel.

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.