课时35整型基础
C的10种整型数据类型
sizeof(char)=1
sizeof(unsigned char)=1
sizeof(short)=2
sizeof(unsigned short)=2
sizeof(int)=4
sizeof(unsigned int)=4
sizeof(long)=4
sizeof(unsigned long)=4
sizeof(long long)=8
sizeof(unsigned long long)=8
请按任意键继续. . .
#include <stdio.h>
#include <stdlib.h>
int main()
{
printf("sizeof(char)=%zd
", sizeof(char));
printf("sizeof(unsigned char)=%zd
", sizeof(unsigned char));
printf("sizeof(short)=%zd
", sizeof(short));
printf("sizeof(unsigned short)=%zd
", sizeof(unsigned short));
printf("sizeof(int)=%zd
", sizeof(int));
printf("sizeof(unsigned int)=%zd
", sizeof(unsigned int));
printf("sizeof(long)=%zd
", sizeof(long));
printf("sizeof(unsigned long)=%zd
", sizeof(unsigned long));
printf("sizeof(long long)=%zd
", sizeof(long long));
printf("sizeof(unsigned long long)=%zd
", sizeof(unsigned long long));
system("pause");
return 0;
}
课时40整型数据的存储（字节序）
int data = 0x12345678;
#include <stdio.h>
#include <stdlib.h>
int main()
{
int data = 0x12345678;
char *p = (char *)&data;
printf("%p %hhx
", &(p[0]), p[0]);
printf("%p %hhx
", &(p[1]), p[1]);
printf("%p %hhx
", &(p[2]), p[2]);
printf("%p %hhx
", &(p[3]), p[3]);
system("pause");
return 0;
}
输出
00000034B476FBE4 78
00000034B476FBE5 56
00000034B476FBE6 34
00000034B476FBE7 12
请按任意键继续. . .
78是低字节，12是高字节。
这是小端字节序
字节序分为：小端字节序，大端字节序、网络字节序。
小端字节序：低字节存于内存低地址；高字节存于内存高地址。
大端字节序：高字节存于内存低地址；低字节存于内存高地址。
网络字节序作为中介，是大端字节序。
课时41整型转换、扩展与截断
扩展：
char src;
int dst;
dst = (char)src;
src有符号，扩展位=符号位，符号位0扩展位也是0，符号位1扩展位也是1
src无符号，扩展位=0
截断：
int src;
char dst;
dst =(char)src;
从低字节开始，截取sizeof(dst)个字节的十六进制数值
整型转换，只与十六进制数值有关系
int i = -1;
整数-1
0xFFFFFFFF十六进制数值
扩展：
int to unsigned int
#include <stdio.h>
#include <stdlib.h>
int main()
{
int int_num = -1;
unsigned int uint_num = (unsigned int)int_num;//强制转换，显式转换
printf("%x %d
", int_num, int_num);
printf("%x %u
", uint_num, uint_num);
system("pause");
return 0;
}
ffffffff -1
ffffffff 4294967295
请按任意键继续. . .
char to int
char to unsigned int
#include <stdio.h>
#include <stdlib.h>
int main()
{
char char_num = -1;
int int_num = (int)char_num;
unsigned int uint_num = (unsigned int)char_num;
printf("%hhx %hhd
", char_num, char_num);
printf("%x %d
", int_num, int_num);
printf("%x %u
", uint_num, uint_num);
system("pause");
return 0;
}
ff -1
ffffffff -1
ffffffff 4294967295
请按任意键继续. . .
char to int
char to unsigned int
#include <stdio.h>
#include <stdlib.h>
int main()
{
char char_num = 1;
int int_num = (int)char_num;
unsigned int uint_num = (unsigned int)char_num;
printf("%hhx %hhd
", char_num, char_num);
printf("%x %d
", int_num, int_num);
printf("%x %u
", uint_num, uint_num);
system("pause");
return 0;
}
1 1
1 1
1 1
请按任意键继续. . .
unsigned char to int
unsigned char to unsigned int
#include <stdio.h>
#include <stdlib.h>
int main()
{
unsigned char char_num = 0xFF;
int int_num = (int)char_num;
unsigned int uint_num = (unsigned int)char_num;
printf("%hhx %hhd
", char_num, char_num);
printf("%x %d
", int_num, int_num);
printf("%x %u
", uint_num, uint_num);
system("pause");
return 0;
}
ff -1
ff 255
ff 255
请按任意键继续. . .
截断：
#include <stdio.h>
#include <stdlib.h>
int main()
{
int int_num = -0x12345678;
short short_num = (short)int_num;
unsigned short unshort_num = (unsigned short)int_num;
printf("int %x %d
", int_num, int_num);
printf("short %hx %hd
", short_num, short_num);
printf("unshort %hx %hu
", unshort_num, unshort_num);
system("pause");
return 0;
}
int edcba988 -305419896
short a988 -22136
unshort a988 43400
请按任意键继续. . .
课时42整型常量
sizeof(0xFFLL), sizeof(0xFFLLu)//long long, unsigned long long
sizeof(0xFFL), sizeof(0xFFLu)//long, unsigned long
#include <stdio.h>
#include <stdlib.h>
int main()
{
printf("sizeof %u %u
", sizeof(0xFFLL), sizeof(0xFFLLu));//long long, unsigned long long
printf("sizeof %u %u
", sizeof(0xFFL), sizeof(0xFFLu));//long, unsigned long
system("pause");
return 0;
}
sizeof 8 8
sizeof 4 4
请按任意键继续. . .