C language - Growth Diary -02- function

 

In the beginning c When it comes to language , It is quite possible that the sum , The code will be the same as shown above . We can write a code segment for summation , Then write the following code by copying and pasting .

Oneortwo lines of code , but , If it is tens of thousands of lines of code , Hundreds of summations , Then this method of writing step by step may not be so easy to use . And this form of expression has a proper noun ：code duplication Code copy .

Code duplication is a sign of poor program performance . Because the copied code segment , Errors may occur in the future . Then it is not as simple as changing oneortwo lines of code , Instead, modify the copied code .

Is there a way , We can make the code more efficient ？

This is the topic I want to write today , function .

Let's bring out the repeated part , Written in the form of a function .

Suppose this function is called sum

sum(   ,   ) Before and after the comma can be recorded as two variables , When you declare a function, you also write ,void sum(int begin,int end)

These two places are the places where the user enters the value he entered in the main function .

sum The function says

int i; ( It can be understood as an intermediate variable i )

int sum=0;  // initialization sum

for loop (i=begin;i<=end;i++)

{

sum+=i;

}   

You mean for ：i from begin Start , To end end ,sum=sum+i namely ： Sum up .

Then output printf......

It can be seen clearly , Although it's a little long to write functions , But it is very convenient to use ！

Calling in main function , Just write the function name and the number of the required sum .

Very convenient ！ And the interface looks very simple ！

Even if there is a need for modification in the future , We only need to modify the function body itself , Instead of modifying a lot of lines of code .

The existence of function , It greatly simplifies the complexity of writing programs , And it improves efficiency , It looks very comfortable ！ 

Think hard when you see problems , Xiao Zhang grew up with you ！

c Language novices are just beginning to blog , There are many places that are not in place csdn My friends give me more advice ！

Thank you very much. ！