Cell growth. Kwon N0=100, k=0.01, t=10.
Nt=N0*ekt
#include <iostream.h>
void main()
{int n0,nt,t;float k;
n0=100,k=0.01,t=10;
nt = n0e^k*t);
cout<<nt<<endl;
}
Program by a good student.
/*********************************************************/
/* cell_growth.cpp - VC5.0 */
/* Cell growth */
/* Hao Xuesheng, 21-Feb-2001 */
/*********************************************************/
#include <iostream.h>
#include <math.h>
void main()
{
int n0; // Initial cell number
int nt; // final cell number
float k; // growth rate
int t; // time
cout << "Initail cell number: ";
cin >> n0;
cout << "Growth rate: ";
cin >> k;
cout << "Time: ";
cin >> t;
nt = n0*exp(k*t);
cout << "Final cell number: " << nt << endl;
}
Output
Initial ell number: 1000
Growth rate: 0.01
Time: 10
Final cell number: 1105
Problem when k is big enough.
Output
Initial ell number: 1000
Growth rate: 0.5
Time: 10
Final cell number: 1105
|
N0 |
K |
t |
Nt |
|
10 |
0.01 |
1 |
|
|
100 |
0.01 |
10 |
|
|
1000 |
0.02 |
10 |
|
|
1000 |
0.05 |
100 |
|
Area of a triangle
Very bad rubbish program!
#include <stdio.lib>;
void main()
{float a,b,c;s;area;
scanf('%d,%d,%d',a,b,c)
s=1/2(a+b+c);
area=sqr(s(s-a)(s-b)(s-c);
print("%d)",arae)
}
Only 1 error and 1 warning when compiling
d:\jc\01\jx\c\triangle_err\triangle_err.cpp(1) : warning C4067: unexpected tokens following preprocessor directive - expected a newline
d:\jc\01\jx\c\triangle_err\triangle_err.cpp(1) : fatal error C1083: Cannot open include file: 'stdio.lib': No such file or directory
Change: stdio.lib à stdio.h
triangle_err.obj - 10 error(s), 1 warning(s)
Even worse with warning!
#include <stdio.h>;
#include <math.h>;
void main()
{float a,b,c,s,area;
scanf("%d,%d,%d",a,b,c);
s=1/2*(a+b+c);
area=sqrt(s*(s-a)*(s-b)*(s-c));
printf("%d)",area);
}
Getting closer
#include <stdio.h>;
#include <math.h>;
void main()
{float a,b,c,s,area;
scanf("%f,%f,%f",&a,&b,&c);
s=1.0/2*(a+b+c);
area=sqrt(s*(s-a)*(s-b)*(s-c));
printf("%f)",area);
}
/*********************************************************/
/* area.cpp - VC5.0 */
/* Arae of a triangle */
/* J Luo, 21-Feb-2001 */
/*********************************************************/
#include <iostream.h>
#include <math.h>
void main()
{
float a, b, c; // sides of the triangle
float s;
float area;
cout << "The sides of a triangle: ";
cin >> a >> b >> c;
s = 0.5F*(a+b+c);
area = (float) sqrt(s*(s-a)*(s-b)*(s-c));
cout << "Area = " << area << endl;
}
Output
The sides of a triangle: 3 4 5
Area = 6
With double
/*********************************************************/
/* area.cpp - VC5.0 */
/* Arae of a triangle */
/* J Luo, 21-Feb-2001 */
/*********************************************************/
#include <iostream.h>
#include <math.h>
void main()
{
double a, b, c; // sides of the triangle
double s;
double area;
cout << "The sides of a triangle: ";
cin >> a >> b >> c;
s = 0.5*(a+b+c);
area = sqrt(s*(s-a)*(s-b)*(s-c));
cout << "Area = " << area << endl;
}
Output
The sides of a triangle: 3 4 5
Area = 6
The sides of a triangle: 3 4 7
Area = 0
The sides of a triangle: 3 4 5
Area = -1.#IND
试计算从公元元年元月元旦一直到2001年元旦为止，期间经历了多少个月、多少个星期、多少天、多少个小时、多少分钟和多少秒钟。并看看能否知道是星期几。
在编写这个程序前，应该考虑以下几点：
· 将程序编写成与计算机会话的形式，以增加趣味性。
· 程序应该有通用性，不仅适用于2001年元旦，也适用于其它年份的元旦。
· 我们知道，逢四的年份是闰年。但是，100, 1900年等逢百的年份不是闰年，而逢百的年份中，1600，2000等逢四百的年份却又是闰年。根据以上规则，可以用下面的公式计算公元元年元月元旦到2001年元旦前一天(即2000年12月31日)为止的天数：
2000×365 + 2000/4 - 2000/100 + 2000/400
· 根据年历的有关规定，公元元年元月元旦为星期一，以上求得的天数再加1，就是到2001年元旦的天数，用它除以7得到的余数，就可以用来表示星期几。
下面，我们给出了这一实例的程序，供大家参考。程序中有几点需要说明的地方：
(1) 考虑到程序的通用性，程序一开始读入年份Year，这就不仅适用于2001年，也适用于其它年份。
(2) 由于C语言中整数的取值范围远比实数的取值范围小，在计算从公元元年元月元旦一直到今天经历了多少秒钟时，其结果会超出整数的范围，因此我们用实数存放秒数。此外，虽然小时数和分钟数虽然不超出整数范围，但它们也都是很大的数字，输出结果中用数量级表示就可以了，因此也都用实数表示。
(3) 在计算天数Days时，用了四个连续的赋值语句，而不是直接用上面的计算公式。把一个比较复杂的表达式拆分成几个简单的表达式，可以减少书写表达式时的错误，这也是程序设计中常用的方法。
(4) 程序中使用了一个getchar()函数，其作用是在运行过程中起到“暂停”的作用，以便看清屏幕上的输出信息。按任意一个键，就可以继续程序的运行。
(5) 程序中用了一个求余算法来计算某一天是星期几，即计算出天数Days后，将其除以7，所的余数就是星期几。在还没有进一步学习有关语句和控制结构前，我们还不能直接打印输出Sunday, Monday等星期几的信息，只能用数字来表示，如0表示星期日，1表示星期一等。
/*********************************************************/
/* what_day.cpp - VC6.0 */
/* What day today? */
/* J Luo, 21-Feb-2001 */
/*********************************************************/
#include <iostream.h>
#include <stdio.h>
void main()
{
int year, months, weeks, days;
double hours, minutes, seconds;
int number;
cout << " ***** Happy New Millennium 2001! ***** \n\n";
year = 2001;
cout << "\n OK! Now I can tell you the number of: \n";
cout << " Months, weeks, days, hours, minutes and seconds, \n";
cout << " since the 1st January 1, till 1 Jan 2001 \n\n";
cout << " Believe so? \n";
year = year - 1;
months = year * 12;
days = year * 365;
days = days + year/4;
days = days - year/100;
days = days + year/400;
weeks = days/7;
hours = days * 24;
minutes = hours * 60;
seconds = minutes * 60;
cout << " Here we are: \n\n";
cout << " Months: " << months << endl;
cout << " Weeks: " << weeks << endl;
cout << " Days: " << days << endl;
cout << " Hours: " << hours << endl;
cout << " Minutes: " << minutes << endl;
cout << " Seconds: " << seconds << endl;
cout << " Am I clever? :-) \n";
cout << " Any more information? \n\n";
getchar();
cout << " Yes, I want to know what day is today? \n\n";
cout << " Let me try ... \n";
days = days + 1;
number = days%7;
getchar();
cout << " OK! I can tell you the number of the day. \n";
cout << " It is : " << number << endl;
cout << " And you can look through the table below: \n\n";
cout << " 0 - Sunday 1 - Monday 2 - Tuesday 3 - Wednesday \n";
cout << " 4 - Thursday 5 - Friday 6 - Saturday \n\n";
cout << " Thanks, but I want to know: 'What Day is today!' \n";
cout << " I don't like the silly numbers! \n\n";
cout << " Let me try again ... \n";
getchar();
cout << " Sad! I can't do it now. :-( \n";
cout << " I will study hard to learn more about c programming! \n\n";
cout << " ***** Good-Bye ***** \n\n";
}
Output
***** Happy New Millennium 2001! *****
OK! Now I can tell you the number of:
Months, weeks, days, hours, minutes and seconds,
since the 1st January 1, till 1 Jan 2001
Believe so?
Here we are:
Months: 24000
Weeks: 104355
Days: 730485
Hours: 1.75316e+007
Minutes: 1.0519e+009
Seconds: 6.31139e+010
Am I clever? :-)
Any more information?
Yes, I want to know what day is today?
Let me try ...
OK! I can tell you the number of the day.
It is : 1
And you can look through the table below:
0 - Sunday 1 - Monday 2 - Tuesday 3 - Wednesday
4 - Thursday 5 - Friday 6 - Saturday
Thanks, but I want to know: 'What Day is today!'
I don't like the silly numbers!
Let me try again ...
Sad! I can't do it now. :-(
I will study hard to learn more about c programming!
***** Good-Bye *****
Not only 2001!
cout << " ***** Happy New Year! ***** \n\n";
cout << " But tell me which year is it? ";
cin >> year;