C

安装

下载离线安装包iso文件，加载之后选择安卓，如果要写c/c++记得勾选widows sdk .

VS控制台程序运行一闪而过的完美解决办法

在你的项目条目（project）上右击鼠标，在弹出菜单上选择最后一项“property/属性”，在左边的一栏里找到“配置属性->链接器->系统”，点击“系统”项后，在右边的栏的“子系统（subSystem）”将刻项的值配置为"Console(/SUBSYSTEM:CONSOLE)"。

调试时不再用F5键，改成Ctrl+F5键。

hello world

#include <stdio.h>

int main()
{
	printf("help");
	return 0;
}

数据类型

位： 最小存储单位bit ，可容纳 0 和 1 。
字节： byte常用存储单位。一般来说，1byte=8bit，可表示0~255整数或字符。
字： word自然存储单位。现使用64位系统，即1字为64位。

#include <stdio.h>
#include <inttypes.h>

int main()
{
	// 整数类型
	int i = 1024;
	printf("I am %d years old 
" , i);
	printf("sizeof int is %d 
", sizeof(i));

	printf("i dec = %d; octal = %o ; hex = %x 
", i, i, i);
	printf("i dec = %d; octal = %#o ; hex = %#x 
", i, i, i);

	printf("sizeof short int is %d 
", sizeof(short int));
	short si = 1024;
	printf("print short use %%hd eg %hd 
" , si);

	printf("sizeof long int  is %d 
", sizeof(long int));

	printf("sizeof long long int is %d 
", sizeof(long long int));
	long long lli = 1024;
	printf("pring long long use %%lld eg %lld 
", lli);

	printf("sizeof unsigned int is %d 
", sizeof(unsigned int));
	printf("sizeof unsigned long int is %d 
", sizeof(unsigned long int));

	// char 类型

	char c = 'A';
	printf("size of char is %u 
", sizeof(char));
	printf("printf char use %%c eg %c or %%d eg %d 
", c, c);
	unsigned char	uc = 255;
	printf("char uc is %c ,int uc is %d 
", uc, uc);

	// _Bool 类型 0:flase other:true
	_Bool flag = 2;
	printf("size of _Bool is  %d 
", sizeof(_Bool));
	printf("printf _Bool eg %d 
", flag);

	// 可移植类型 inttypes.h
	int16_t me16 = 4593;
	printf("me16 = %hd 
", me16);
	printf("me16 = %"PRId16"
", me16);

	// float / double / long double 类型
	float ff = 10e9;
	double dd = 10e9;
	long double ld = 10e9;

	printf("size of float is %d 
", sizeof(float));
	printf("size of double is %d 
", sizeof(double));
	printf("size of long double is %d 
" , sizeof(long double));

	printf("%f can ber written %e
", ff, ff);
	printf("%f can ber written %e
", dd, dd);
	printf("%f can ber written %e
", ld, ld);

	return 0;
}

字符串输入输出

关于使用VS会出现scanf要用scanf_s的处理：Alt+F7，打开工程属性，c/c++ 预处理器定义，添加一行内容_CRT_SECURE_NO_DEPRECATE就OK了

#include <stdio.h>
#define HI "ni hao a ! "

int main()
{
	// 字符串输入输出
	char name[40];

	printf("What's your name ?
");
	scanf("%s", name);
	printf("%s , %s 
", HI, name);
	return 0;
}

格式化输出

#include <stdio.h>
#include <string.h>

int main()
{
	// 字符串函数
	char name[40]  = "qianqian.sun";

	printf("size of name is %u 
", sizeof(name)); // 40
	printf("length of name is %d 
 ", strlen(name)); // 12

	printf("
使用修饰符 和 转换符打印表格
");
	for (int i = 0; i < 25; i++)printf("-"); printf("
");
	printf("| %5s | %5s | %5s | 
", "姓名", "年龄", "身高");
	for (int i = 0; i < 25; i++)printf("-"); printf("
");

	printf("| %5s | %5d | %5.2f | 
","前前",24,1.85);
	for (int i = 0; i < 25; i++)printf("-"); printf("
");

	// * 修饰符
	printf("可指定宽度和精度:%*d
", 5, 100);
	printf("可指定宽度和精度:%*.*f
", 10,2, 10.0);
	int  width, precision;
	scanf("%*d %d %d", &width, &precision); // 跳過第一个参数
	printf(" Value = %*.*f 
", width, precision, 66.6);

	return 0;
}

字符的输入输出

字符与单词统计

#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>


int main()
{
	int ch;
	FILE * fp;
	char name[50] = "C:/share/PostLoanData/file.txt";

	fp = fopen(name, "r");
	if (NULL == fp)
	{
		printf("Fail to open file 
");
		exit(1);
	}
	int count, lower_count, upper_count, word_len, word_count,cur_word;
	count = lower_count = upper_count = word_len = word_count = cur_word =0;
	while ((ch = getc(fp)) != EOF)
	{
		switch (ch)
		{
		case '
':
			printf("\n");
			break;
		case '	':
			printf("\t");
			break;
		default:
			putchar(ch);
			break;
		}
		printf(": %d |", ch);
		if (++count % 10 == 0)printf("
");
		if (islower(ch)) lower_count++;
		if (isupper(ch)) upper_count++;
		if (isalpha(ch)) cur_word++; // 字母则累计
		if (isdigit(ch)) cur_word = 0; //遇到 数字 则清零
		if ((isspace(ch) || ispunct(ch)) && cur_word>0)
		{
			word_count++;
			word_len += cur_word;
			cur_word = 0; //空白 标点则判断当前是否为单词
		}
	}
	if (cur_word>0)
	{
		word_count++;
		word_len += cur_word;
	}
	fclose(fp);
	printf("
 字符总数: %5d 
", count);
	printf("大写字母数: %d , 小写字母数: %d 
", upper_count, lower_count);
	printf("大写字母数: %d , 小写字母数: %d 
", upper_count, lower_count);
	printf("word_len = %d 
", word_len);
	printf("单词总数: %d , 平均长度: %5.2f 
", word_count, (double)word_len/ word_count);
	return 0;
}