C语言学习笔记[第5天]2022.11.15

三、数据和C

4. C语言基本数据类型

4.2 其他整数类型

4.3 使用字符：char 类型

​ ■整数常量例子

类型	十六进制	八进制	十进制
char	\x41	\101	N.A.
int	0x41	0101	65
unsigned	0x41u	0101u	65u
long	0x41L	0101L	65L
unsigned long	0x41UL	0101UL	65UL
long long	0x41LL	0101LL	65LL
unsigned long long	0x41ULL	0101ULL	65ULL

​ ■打印字符

/* charcode.c-显示字符的代码编号 */
#include <stdio.h>
int main(void)
{
    char ch;
    
    print("Please enter a character.\n");
    scanf("%C",&ch);
    print("The code for %c is %d.\n",ch,ch);
    
    return 0;
}
//Please enter a character.
//C
//The code for C is 67. 

4.4 _Bool类型

​ ■true和false

4.5 可移植类型：stdint.h和inttypes.h

​ ■精确宽度整数类型

​ ■最小宽度类型

/* altnames.c -- 可移植整数类型名 */
#include <stdio.h>
#include <inttypes.h> //支持可移植类型
int main(void)
{
    int32_t me32;	// me32是一个 32 位有符号整型变量
    
    me32 =45933945;
    printf("First, assume int32_t is int:");
    printf("me32 = %d\n", me32);
    printf("Next, let's not make any assumptions.\n");
    printf("Instead, use a \"macro\" from inttypes.h:");
    printf("me 32 = %" PRID32 "\N", me32);
    
  	return 0;
}

//First, assume int32_t is int: me32 = 45933945
//Next, let's not make any assumptions.
//Instead, use a "macro" from inttypes.h: me 32 = 45933945

4.6 float、double和long double

​ ■记数法示例

数字	科学计数法	指数计数法
1000000000	1.0×10⁹	1.0e9
123000	1.23×10⁵	1.23e5
322.56	3.2256×10²	3.2256e2
0.000056	5.6×10⁻⁵	5.6e-5

​ ■声明浮点型变量

float noah,jonah;
double troble;
float plank = 6.63e-34;
long double gnp;

​ ■浮点型常量

​ -1.56E+12

​ 2.87E-3

​ 3.14159

​ .2

​ 4e16

​ .8E-5100.

​ ■打印浮点值

/* showf_pt.c -- 以两种方式显示 float 类型的值 */
#include <stdio.h>
int main(void)
{
    float aboat = 32000.0;
    double abet = 2.14e9;
    long double dip =  5.32e-5;
    
    printf("%f can be written %e\n", aboat, aboat);
    // 下一行要求编译器支持C99或其中的相关特性
    printf("And it's %a in hexadecimalm, power of 2 notation\n", aboat);
    printf("%f can be written %e\n", abet, abet);
    printf("%Lf can be written %Le\n", dip, dip);
    
    return 0;
}

//32000.000000 can be written 32000e+04
//And it's 0x1.f4p+14 in hexadecimalm, power of 2 notation
//2140000000.000000 can be written 2.140000e+09
//0.000053 can be written 53320000e-05

​ ■浮点值的上溢和下溢