第一节 很久不见---变量

基本数据所占内存的大小：

#include<stdio.h>

void Interger_type()
{
	//整型
	char c = 'c';
	short st = 1;
	int i = 2;
	long l = 3;
	//无符号整型
	unsigned char uc = 'k';
	unsigned short ust = 4;
	unsigned int ui = 5;
	unsigned long ul = 6;
	
	printf("*****Interger_type*******\n");
	printf("c = %d ,char = %d\n",sizeof(c),sizeof(char)); // 1 , 1
	printf("st = %d ,short = %d\n",sizeof(st),sizeof(short)); // 2 , 2
	printf("i = %d ,int = %d\n",sizeof(i),sizeof(int));   // 4 , 4
	printf("l = %d ,long = %d\n",sizeof(l),sizeof(long));  // 8 , 8
	printf("uc = %d ,unsigned char = %d\n",sizeof(uc),sizeof(unsigned char)); // 1 , 1
	printf("ust = %d ,unsigned short = %d\n",sizeof(ust),sizeof(unsigned short));  // 2 , 2
	printf("ui = %d ,unsigned int = %d\n",sizeof(ui),sizeof(unsigned int));   // 4 , 4
	printf("ul = %d ,unsigned long = %d\n",sizeof(ul),sizeof(unsigned long));  // 8 , 8
	
	printf("\n");
}
void Float_type()
{
	// 浮点型
	float f = 3.401f;
	double d = 3.1415926;
	long double ld = 3.12434455;
	
	//unsigned float uf = 9.8765432; //error 浮点型中的unsigned、short、signed关键字都不适用
	
	printf("*****Float_type*******\n");
	printf("f = %d ,float = %d\n",sizeof(f),sizeof(float));  // 4 , 4 
	printf("d =%d ,double = %d\n",sizeof(d),sizeof(double)); // 8 , 8
	printf("ld =%d ,long double  = %d\n",sizeof(ld),sizeof(long double)); //16 , 16 不同的机器的值会不相同
	//printf("unsigned float = %d\n",sizeof(uf)); //error
	
	printf("\n");
	
}
void Struct_type()
{
	struct TagSIMPLE {
		int i;
		char c;
		short st;
	};
	struct TagSIMPLE tagS = {0,'c',2};
	struct TagSIMPLE* pTagS = &tagS;
	typedef struct {
		int i;
		float f;
		short st;
	} Simple;
	Simple Ts;
	
	printf("*****Struct_type*******\n");
	printf("%d ,%d\n",sizeof(tagS),sizeof(pTagS)); // 8 , 8 
	printf("%d, %c, %d\n",tagS.i,tagS.c,tagS.st);   // 0 , c , 2
	printf("%d ,%d\n",sizeof(Ts),sizeof(Simple*));  // 12 , 8 
	printf("%d, %c, %d\n",Ts.i,Ts.f,Ts.st); // 717254944 , ( , 2147483642 随机值
	printf("\n");
}
void Point_type()
{
	char c = 'c';
	char* pChar = &c;
	short st = 1;
	short* pShort = &st;
	int i = 2;
	int* pInt;
	pInt = &i;
	long l = 3;
	long* pLong;
	pLong = &l;
	
	printf("******Point_type*******\n");
	printf("%d, %d, %d\n",sizeof(pChar),sizeof(char*),sizeof(&c)); // 8 , 8 , 8 
	printf("%p, %p\n",pChar,&c);  // 0x7ffe2ac0712f , 0x7ffe2ac0712f
	
	printf("\n");
}
int main()
{
	Interger_type();
	Float_type();
	Point_type();
	Struct_type();
	return 0;
}

 在Centos上编译结果：