Experiment one

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1. Abbreviated program , Output the following information ： **********￥￥ ￥￥￥ This is my first C program! **********￥￥￥￥￥

#include<stdlib.h>
int main(void)
{
	printf("**********￥￥\n");/*wj*/
	printf("￥￥￥\n");
	printf("This i my first C program!\n");
	printf("**********￥￥￥￥￥\n");
	system("pause");
	return 0;
}```
2. Enter the radius of the cylinder r  And high h, Calculate and output its volume .
```#include<stdio.h>
#include<stdlib.h>
#define PI 3.1415926
int main(void)
{
	float r, h;
	float v;

	printf(" Please enter the radius of the cylinder r:");
	scanf("%f", &r);
	printf(" Please enter the height of the cylinder h:");
	scanf("%f", &h);
	v = PI * r * r * h;
	printf(" The volume of the cylinder v by ：%f", v);
	system("pause");
	return 0;
}```
3. Enter three numbers to variables a,b,c  in , Average them .
```#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
#include<stdlib.h>
int main(void)
{
	int a, b, c;/*number*/
	float aver;

	printf(" Please enter a:");
	scanf("%d", &a);
	printf(" Please enter b:");
	scanf("%d", &b);
	printf(" Please enter c:");
	scanf("%d", &c);
	aver = (a + b + c) / 3.0;
	printf(" The average value is :%f", aver);
	system("pause");
	return 0;
}
4. Enter seconds , Press it by the hour . minute . Seconds to output . For example, the input 24680, The output 6  Hours 51
 branch 20  second .

 ```#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
#include<stdlib.h>
int main(void)
{
	int s;
	int hour, minute, second;/* Company  */

	printf(" Please enter the number of seconds :");
	scanf("%d", &s);
	hour = s/3600;
	minute = (s % 3600) / 60;
	second = s % 60;
	printf("%d The second is equal to %d Hours %d branch %d second ", s, hour, minute, second);
	system("pause");
	return 0;
}```
5.
(1) Write a program to calculate the volume of the sphere , Where the radius of the sphere is 10m（ Pay attention to the way the score is written ）
(2) Modify the procedure in the above question , Allows you to enter the radius of the sphere .
```#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
#include<stdlib.h>
#define PI 3.1415926
int main(void)
{
	float r;/* radius */
	float v;/* Volume */
	printf(" Please enter the radius of the sphere r:");
	scanf("%f", &r);
	v = 4.00/ 3.00* PI * r * r * r;
	printf(" The volume of the sphere v by :%f", v);
	system("pause");
	return 0;
}```
6. Write a program , Use printf  Show the following graphics on the screen ：

#define _CRT_SECURE_NO_WARNINGS #include<stdio.h> #include<stdlib.h> int main(void) { printf(" *\n"); printf(" *\n"); printf(" *\n"); printf(" * *\n"); printf(" * *\n"); printf(" *\n"); system("pause"); return 0; }``` 7. Write a program , Ask the user to enter a dollar variable , And then it shows an increase 5% The corresponding amount after the tax rate forehead , The format is as follows Enter an amount： 100.00 With tax added：$105.00

int main(void)
{
	float money;/* money */
	float moneyWithTax;
	printf("Enter an amount：");
	scanf("%f", &money);
	moneyWithTax = money * (1 + 0.05);
	printf("With tax added：$%.2f",moneyWithTax);
	system("pause");
	return 0;
}```

8.(1) Programming requires user input x  Value , Then display the values of the following polynomials ：
3x5+2x4-5x3-x2+7x-6
```#include<stdio.h>
#include<stdlib.h>
int main(void)
{
	float x, y;/* Count */

	printf(" Please enter x Value :");
	scanf("%f", &x);
	y = 3 * x * x * x * x * x + 2 * x * x * x * x - 5 * x * x * x - x * x + 7 * x - 6;
	printf(" polynomial 3x5+2x4-5x3-x2+7x-6 The value of is :%f", y);
	system("pause");
	return 0;
}```
(2) Revise the question above , Use the following formula to evaluate polynomials 
((((3x+2)x-5)x-1)x+7)x-6

```#include<stdio.h>
#include<stdlib.h>
int main(void)
{
	float x, y;/* Count */
    printf(" Please enter x Value :");
	scanf("%f", &x);
	y = ((((3 * x + 2) * x - 5) * x - 1) * x + 7) * x - 6;
	printf(" polynomial ((((3x+2)x-5)x-1)x+7)x-6 The value of is :%f", y);
	system("pause");
	return 0;
}```
9. Write a program , Ask the user to enter a dollar amount , Then show how to use the least 20  dollar 、10
 dollar 、5  The dollar and 1  Dollars to pay 
Enter a dollar amount:93
$20 bills:4
$10 bills:1
$5 bills:0
$1 bills:3
( Tips ： Divide the payment amount by 20, determine 20  The amount of dollars , And then subtract... From the payment amount 20  The dollar 
 Total sum , Repeat for other denominations , Make sure you use integer values in your program , Don't use floating point numbers )

```#include<stdio.h>
#include<stdlib.h>
int main(void)
{
	int money, twenty, ten, five, one;/*12345*/
	printf("Enter a dollar amount:");
	scanf_s("%d", &money);
	twenty = money / 20;
	money = money - twenty * 20;
	ten = money / 10;
	money = money - ten * 10;
	five = money / 5;
	money = money - 5 * five;
	one = money;
	printf("$20 bills:%d\n", twenty);
	printf("$10 bills:%d\n", ten);
	printf("$5 bills:%d\n", five);
	printf("$1 bills:%d\n", one);
    system("pause");
	return 0;
}```