long int

long int即long，给人的感觉好像是长整型，但实际上，它和int一样，只有32位。cppreference给出的定义是——

int - basic integer type. The keyword int may be omitted if any of the modifiers listed below are used. If no length modifiers are present, it’s guaranteed to have a width of at least 16 bits. However, on 32/64 bit systems it is almost exclusively guaranteed to have width of at least 32 bits.
long - target type will have width of at least 32 bits.

在实际的使用中，long与int几乎没有区别，比如——

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#include<stdio.h>

int main(){
	long l = 10000000;
	int i = 10000000;
	printf("size of long:%d\n",sizeof(long));
	printf("size of int:%d\n",sizeof(int));
 	printf("l = %d\n",l);
 	printf("i = %d\n",i);
	return 0;
}
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　　既然long int与int相同，那么为什么还有long int这种尴尬的类型呢？
　　原因是早期的C编译器定义了long int占用4个字节，int占用2个字节，long int是名副其实的长整型。在ANSI C的标准中，对长整型的定义也是long int应该至少和int一样长，而不是long int 一定要比int占用存储字节长。新版的C/C++标准兼容了早期的这一设定。