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1, literal
3 is 3 and will never be 4.
#include<stdio.h>
int main(){
printf("%d\n",3);
return 0;
}
Effect:
2, const constant
When a variable is const modified, it cannot be assigned again.
The essence is still a variable, but it cannot be assigned a value.
This code throws an error:
#include<stdio.h>
int main(){
const int a=3;
a=4;
printf("%d\n",a);
return 0;
}
Error content:
3, #define constants
#define can define a constant.
#include<stdio.h>
#define hello "你好，世界！"
int main(){
printf("%s\n",hello);
return 0;
}
Effect:
4, enumeration constants
An enumeration represents a listable value, such as:
gender: male, female.
Week: 1 to 7.
enum Gender{
Male,Female
}
Male and female are essentially 0 and 1, which are represented by words, have semantics, and are readable.
Simple to use:
#include<stdio.h>
enum Gender{
Male,Female
};
int main(){
enum Gender a=Male;
enum Gender b=Female;
printf("%d,%d\n",a,b);
return 0;
}
Effect:
5. String
Strings are surrounded by double quotes.
"你好，世界！"
The essence is a char array, and it ends with \0, which is not in the content.
\0 represents the end of the string.
It can be directly assigned to a char array, and then printed as a %s string:
#include<stdio.h>
int main(){
char a[]="你好，世界！\n";
printf("%s",a);
return 0;
}
Effect:
It will end when it encounters \0:
#include<stdio.h>
int main(){
char a[]={
'a','b','c','\0','d'};
printf("%s\n",a);
return 0;
}
Effect:
In the figure, d is not output.
escape character
Some meaningful characters, which are inconvenient to express themselves, are converted:
换行：\n
tab位：\t
字符串结束：\0
单引号：\'
双引号：\"
斜线：\\
Simple to use:
#include<stdio.h>
int main(){
printf("%c\n",'\\');
printf("%c\n",'\'');
printf("%c\n",'\"');
return 0;
}
Effect:
How characters are stored
ASC code, which is seen when the char is output as %d:
#include<stdio.h>
int main(){
printf("%d\n",'A');
printf("%d\n",'a');
printf("%d\n",'0');
return 0;
}
Effect:
