Basic knowledge of functions and special points

1. function .（ High cohesion and low coupling as much as possible ）

• C Classification of functions in language ：
• Library function
• Custom function

• But a secret that library functions must know is ： Use library functions , Must contain #include Corresponding header file .

Here, learn the above library functions by referring to the documentation , The purpose is to master the use of library functions .

• You need to learn how to use query tools ：

MSDN(Microsoft Developer Network)

www.cplusplus.com

cppreference.com（ English version ）

cppreference.com（ Chinese version ）

• Formal parameters and actual parameters

Actual parameters ： The parameters that are actually passed to the function , It's called the actual parameter .

The argument can be ： Constant 、 Variable 、 expression 、 Functions, etc .

Shape parameter ： Formal parameters refer to the variables in brackets after the function name , Because formal parameters are only instantiated when the function is called （ Within distribution

deposit receipt element ）, So it's called formal parameter . Formal parameters are automatically destroyed when the function call is completed . Therefore, formal parameters only exist in functions

effect .

example ： Function call exec((vl,v2),(v3,v4),v5,v6); in , The number of arguments is ：（ ）

example ：

Among them a and b Is the argument ,*px and *py It's a parameter .

• Function call ：

Value transfer call , Pass a value , The address was not passed

The formal and actual parameters of a function occupy different memory blocks , Modification of a parameter does not affect the argument .

Address call

Address call is a way to call a function by passing the memory address of the created variable outside the function to the function parameter .

This parameter transfer method can establish a real relationship between the function and the variables outside the function , That is, you can directly operate inside the function

As a variable outside the function

• Nested function

Nesting is to call a function inside other functions , To recycle , Achieve an effect similar to the cycle , But it reduces the code .

• Chained access

Take the return value of one function as the parameter of another function

• Declaration of functions

If the definition function is after the use function , Declare the function before using it , The declaring function should be declared in the main function

If you define a function before using it , You can use functions directly without declaration . Therefore, we usually define the function first before using the function

• Function recursion

Recursion simply means calling your own functions , So as to achieve the effect of the function .

Two necessary conditions for recursion

There are restrictions , When this constraint is met , Recursion doesn't continue .

After each recursive call, it gets closer and closer to this constraint

example ： Recursively print each bit of an integer

• The creation and destruction of function stack frames
• register

It is divided into eax、ebx、ecx、edx、 as well as ebp and esp

Every function call has to create a space in the stack

main It is also called by other functions .

__tmainCRTStartup Of this function esp and ebp Go through some operations , by main Function creates a space , And then ebx and esi and edi, To operate