0 basic C language (0)

Today, I summoned up a lot of courage to open c The pit of language , because c I don't have a systematic book to read , I learned from the video , So there are some things I forgot that I might need to watch the video again , And some knowledge points may be forgotten and directly dropped , So c Don't like python Same every day , Maybe I have time to be more . In fact, watching the video again also consolidated my memory of knowledge points , I wrote this for notes , When you forget, you can look through . Another difficulty is , I now face a problem , sometimes python Things may be similar to c Remember mix , Because they have a lot in common , And the teachers are all men, and their memories are almost the same , I like to recall the sound scene and the content , If these two are really mixed , In fact, I don't know where to find this point . When writing this note, I will try my best to write out my confusing things .

  c Language and python The essential difference is c Language has a prefix .

#include<stdio.h>
int main()
{

  printf("Hello World!\n");
  return 0;
}

We can also find that the output section hello world from python A few short lines of have become such a large paragraph , In fact, the first three lines and the last two lines are each paragraph c Language code is necessary for runtime , The first line refers to the location of the file , The second line int It is not available at the present position , When we get to the function, we will explain why we should use int, After the braces is where we are going to program , hinder return 0  Is the end of programming position .

Next, let's look at the position we need to program each time, that is, the position inside the braces , from python Of print, Change it to printf Actually f It's formatting format Abbreviation ,

The most fatal thing is not these changes, but the latter ; Every time you finish programming, you should check it first. You should add ; Is there any place where , I dare to start compiling , Early because of this ; Wasted a lot of time , Usually after typing a piece of code , For the output , Obviously, it's the same as the one in the video, but it can't be compiled , After checking for a long time, it was found that such a small symbol was not written , It's very hard .

So every time I finish writing the code, I have to see if there are any places that should be added , So far I have learned , Add... After the loop and at the end of the loop ;. Because of this ; It is equivalent to telling the computer that this code is at the end , This is important for computers .

Look again printf（） What's inside ,"" The contents are called strings printf It will output the contents intact , This one at the back \n It means to replace the output result with a new line .

For us, Chinese input method can be very deadly , Because the Chinese input method outputs symbols that are very similar to the English output , But the computer may be composed of several characters when understanding Chinese symbols , At the same time, it is very difficult to find errors in using Chinese characters , Therefore, when writing code, it is always in the state of English input .

When we are going to do an operation, we need to use &d, What we will enter is such a piece of code

printf("%d\n",23+43)

We type in &d This indicates that there is an integer to be output at this position , After the comma is what we are going to output .

c Four budgets in language and python It's about the same +（ Add ）-（ reduce ）*（ ride ）/（ except ）%（ Remainder ）（）（ Brackets ）

among % Represents the remainder after dividing two numbers .