[C language series] - string + partial escape character explanation + annotation tips

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*  Blog column ：【C All living things 】*

Introduction to this article ： character string + Partial escape character + Notes tips detailed introduction ！

Get to know the author ： Aspire to be a great programmer , Xiaobai, who is currently a sophomore in College .

Inspirational terms ： The tediousness of programming , Let's study together and become interesting ！

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List of articles

character string

Escape character

Summary of common escape characters

Explanation of several common escape characters

 \?

\'（\"）

\ddd

 \xdd

Notes tips

Conclusion

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character string

Let's first look at a small piece of code ：

”hello world.\n"

Last time we mentioned characters （ Like this, ‘w’ ）, It's just a character , Such a string composed of multiple characters with double quotation marks is called the literal value of the string （String Literal）, Abbreviated string .

Here I want to give you a small note , Also very important is ：

The end of a string is a ‘\0’ The escape character of , When calculating the length of a string ‘\0’ It's the end sign , But it doesn't count the contents of the string .

Learned knowledge , Let's do a code topic     ——————>>>

#include<stdio.h>
int main()

{
	char arr1[] = "abc";
	char arr2[] = { 'a','b','c' };
	char arr3[] = { 'a','b','c','\0' };
	printf("%s\n", arr1);
	printf("%s\n", arr2);
	printf("%s\n", arr3);
	return 0;
}

Let's try , Ask what these three print respectively ？

Ha ha ha , Here we should highlight '\0' The importance of , Let's analyze this code ,

After the analysis , Let's take a look , Print the results ,

The result print of code 2 appears ,（ To scald ） Such random values

Escape character

Before talking about escape characters , Let's first look at a written test question about escape characters

#include<stdio.h>
int main()
{
	printf("c:\code\test.c\n");
	return 0;
}

  As you can see, there are many in this code With '\' start , Form followed by a letter , Some of these are escape characters ,

Let's analyze this code .

Look at the print results after analysis , Is it the same as a feather ------------->>>

Next, let's learn more about escape characters , First, let's look at a summary of strings ！

Summary of common escape characters

Explanation of several common escape characters

 \?

Speaking of \? This escape character , It should be supported by compilers a long time ago （ such as ：VC 6.0）, This compiler

Add a   \ Then it will not be parsed into three letter words , Of course, this is now vs2013 The above version cannot be demonstrated , So there's no demonstration ！

\'（\"）

When you just want to print on the screen \' What to do when , Look at this little code

#include<stdio.h>
int main()
{
	printf("%c\n", '\'');
	return 0;
}

  The result of this printing is a single ‘ Character

\ddd

The demonstration of escape characters also depends on a piece of code and analysis ！

#include<stdio.h>
int main()
{
	printf("%c\n", '\130');
	return 0;
}

Look at the results

  Why do you print uppercase characters X Well ？ This is just like ASCII The code table is related to , interested , You can search the Internet ASCII Look at the code table , I won't explain it in detail here ！

 \xdd

#include<stdio.h>
int main()
{
	printf("%c\n", '\x30');
	return 0;
}

Here corresponds to hexadecimal conversion

  Let's see the result

summary ： Escape characters are so simple , I've learned , Iron ！！！

Notes tips

When we write code in the source file, we usually need to write some comments , When writing wrong code , But I don't want to delete , At this time, you need the annotation function of the compiler , Introduce two annotation methods

There are two styles of annotation ：
C Notes on language style  /*xxxxxx*/
defects ： You can't nest comments
C++ Style notes  //xxxxxxxx
You can comment on one line or multiple lines

Conclusion

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