What is a function?
Functions are designed to solve a large number of problems of the same type. Functions are a tool
The basic unit of the C language is the function
Functions can be treated as a black box
Why do you need functions?
1. Avoid repetitive operations
2. Conducive to the modularization of the program
It is very simple to use a thing, but why this thing was born is also worth exploring
The black box can be used, but I don’t know how to deal with it internally
What is a function?
4 minutes 30
logically:
An independent block of code that performs a specific function
Physically:
Can receive data [of course, you can not receive data]
able to process the received data
Can return the result of data processing [of course, you can also not return any value]
How to define a function?
1. The essence of a function definition is to describe in detail how a function can achieve a specific function
2. The type of the return value of a function is also called the type of the function. If the type of the return value before the function name is different from the type in the return expression in the function execution body, the type of the return value of the final function will be the return value before the function name. Type prevails
for example:
int test()
{
return 8.8; // 因为函数的返回值类型是int 所以最终返回的值是8
} return terminates the function
If the expression is empty, that is, return is empty, only the function is terminated, and no value is returned to the called function
Classification of functions
Functions with and without parameters
Functions that return a value and functions that do not return a value
library functions and user-defined functions
Ordinary functions and main functions
A program must have one and only one main function
The main function can call ordinary functions Ordinary functions cannot call the main function
Ordinary functions can call each other
The main function is the entry of the program and the exit of the program