经典编程900例（c语言）（第二篇）

例11：浮点数的科学计数法

#include <stdio.h>

int main(int argc, char const *argv[])
{
	float value = 1.23456;

	// 输出宽度12保留1位小数的科学计数法表示
	printf ("%12.1e\n", value);

	// 输出宽度12保留3位小数的科学计数法表示
	printf ("%12.3e\n", value);

	// 输出宽度12保留3位小数的科学计数法表示
	printf ("%12.5e\n", value);
	
	return 0;
}

例12：浮点数计算科学计数法

#include <stdio.h>

int main(int argc, char const *argv[])
{
	// π
	float pi = 3.14159;

	// 半径
	float radius = 2.0031;

	// 根据半径计算周长=2*π*r
	printf("The circle's area is %e\n", 2 * pi * radius);	// The circle's area is 1.258584e+001
	printf("The circle's area is %E\n", 2 * pi * radius);	// The circle's area is 1.258584E+001
	return 0;
}

例13：控制台输出函数

#include <stdio.h>

int main(int argc, char const *argv[])
{
	// 调用函数（需包含stdio.h）
	printf("1001 C & C++ Tips!");	// 1001 C & C++ Tips!

	return 0;
}

例14：浮点数输出

#include <stdio.h>

int main(int argc, char const *argv[])
{
	float price = 525.75;
	float sales_tax = 0.06; 

	// %f打印浮点数
	printf("The item cost is %f\n", price);						// The item cost is 525.750000
	printf("Sales tax on the item is %f\n", price * sales_tax);// Sales tax on the item is 31.544999

	return 0;
}

例15：浮点数的输出控制

#include <stdio.h>

int main(int argc, char const *argv[])
{
	float value = 1.23456;

	// 输出宽度8保留1位小数
	printf ("%8.1f\n", value);
	// 输出宽度8保留3位小数
	printf ("%8.3f\n", value);
	// 输出宽度8保留5位小数
	printf ("%8.5f\n", value);
	
	return 0;
}

例16：%g在printf中的特点

#include <stdio.h>

int main(int argc, char const *argv[])
{
	// %g根据数值的大小，自动选f格式或e格式（选择输出时占宽度较小的一种）
	printf("Displaying 0.1234 yields %g\n", 0.1234);
	printf("Displaying 0.00001234 yields %g\n", 0.00001234);

	return 0;
}

例17：两个循环变量

#include <stdio.h>

int main(int argc, char const *argv[])
{
	int i, j;

	// i从1到100,j从100-200,每次+1,依次输出
	for (i = 0, j = 100; i <= 100; i++, j++)
		printf("i = %d j = %d\n", i, j);

	return 0;
}

例18：循环变量的步长控制

#include <stdio.h>

int main(int argc, char const *argv[])
{
	int counter;

	// 从-100开始,小于等于100就循环,每次+5
	for (counter = -100; counter <= 100; counter += 5)
		printf("%d ", counter);

	printf("\nStarting second loop\n");

	// 从100开始,大于等于-100就循环,每次-25
	for (counter = 100; counter >= -100; counter -= 25)
		printf("%d ", counter);

	return 0;
}

例19：循环条件的判断

#include <stdio.h>

int main(int argc, char const *argv[])
{
	int counter;

	for (counter = 5; counter >= 1; counter--)
		printf("%d ", counter);

	printf("\nStarting second loop\n");
	for (counter = 10; counter >= 1; counter--)
		printf("%d ", counter);

	printf("\nStarting third loop\n");
	// 从0开始,大于等于1就循环,每次-1,不打印
	for (counter = 0; counter >= 1; counter--)
		printf("%d ", counter);

	return 0;
}

例20：char和float的for循环

#include <stdio.h>

int main(int argc, char const *argv[])
{
	char letter;
	float percent;

	// 从A开始,小于等于Z就循环,每次+1
	for (letter = 'A'; letter <= 'Z'; letter++)			//ABCDEFGHIJKLMNOPQRSTUVWXYZ
		putchar(letter);

	// 从z开始,大于等于a就循环,每次-1
	for (letter = 'z'; letter >= 'a'; letter--)			// zyxwvutsrqponmlkjihgfedcba
		putchar(letter);

	putchar('\n');										// 换行

	// 从0.0开始,小于1.0就循环,每次+0.1
	for (percent = 0.0; percent < 1.0; percent += 0.1)	// 0.0<换行>
		printf("%3.1f\n", percent);

	return 0;
}

例21：for循环

#include <stdio.h>

int main(int argc, char const *argv[])
{
	int counter;

	for (counter = 1; counter <= 5; counter++)
	printf("%d ", counter);

	printf("\nStarting second loop\n");

	for (counter = 1; counter <= 10; counter++)
	printf("%d ", counter);

	printf("\nStarting third loop\n");

	for (counter = 100; counter <= 5; counter++)
	printf("%d ", counter);

	return 0;
}

例22：输出格式控制

#include <stdio.h>

int main(int argc, char const *argv[])
{
	int int_value = 5;

	// -表示左对齐输出（默认右对齐），+表示带正负号，3表示宽度
	printf("Left justifed with sign %-+3d##\n", int_value);	// Left justifed with sign +5 ##

	return 0;
}

例23：goto语句的使用

#include <stdio.h>
/*
 * 这段代码可以实现循环，一个没有for和while的循环
 * （学过汇编的同学可能会很熟悉）
 */
int main(int argc, char const *argv[])
{
	int count = 1;

	// 定义标记label,冒号后接语句
	label:
		printf("%d ", count++);

	// 如果count小于等于100就跳到label标记处运行
	if (count <= 100)
		goto label;

	
	return 0;
}

例24：一段难看的代码

#include <stdio.h> 
int main(int argc, char const *argv[]){{printf("1001 C & C++ Tips!");}return 0;}

例25：一段好多注释的代码

/* Program: COMMENT.C*/
/* Written by: Kris Jamsa*/
/* Date written: 06-30-93*/

/* Purpose: Illustrates the use of comments in a C program.*/

#include <stdio.h>

int main(int argc, char const *argv[])
{
	printf ("1001 C & C++ Tips!");  /* Display a message*/
	return 0;
}

例26：又一段好多注释的代码

/* Program: COMMENT.C
   Written by: Kris Jamsa
   Date written: 06-30-93

   Purpose: Illustrates the use of comments in a C program. */

#include <stdio.h>

int main(int argc, char const *argv[])
{
	printf ("1001 C & C++ Tips!");  /* Display a message */
	
	return 0;
}