24---------------------------------
#include <stdio.h>
void main()
{
	int number;

	printf("Input a number:\n");
	scanf("%d",&number);

	printf("%o , %x \n",number,number);
}
25---------------------------------
#include <stdio.h>
void main()
{
	int letter=0,blank=0,number=0,other=0,
	char ch;

	printf("Input a string:");
	ch=getchar();
	while (ch!='\n')
	{if((ch>='a'&&ch<='z')||(ch>='A'&&ch<='Z'))
	letter++;
	else if (ch==' ')
	blank++; 
	else if (ch>='0'&&ch<='9')
	number++;
	else other++;

	ch=getchar();
	}

	printf("letter=%d,blank=%d,number=%d,other=%d\n",letter,blank,number,other);
}
26---------------------------------
#include <stdio.h>
void main()
{
	int letter=0,s;
	char ch;

	printf("Input a string:\n");

	ch=getchar();

	while (ch!='\n')
	{
		s=1;

		while (ch!=' '&&ch!='\n')
		{
			ch=getchar();
			letter=letter+s;
			s=0;
		}
		
		
		if (ch=='\n')
		break;
	
		ch=getchar();
	}

	printf("letters=%d\n",letter);
}
27---------------------------------
#include <stdio.h>
void main()
{
	int a,b,flag=1;
	char ch;

	printf("Input a formula:\n");
	scanf("%d",&a);
	ch=getchar();

	while (ch!='=')
	{
		scanf("%d",&b);

		switch(ch)
		{
		case '+':a=a+b;
			break;
		case '-':a=a-b;
			break;
		case '*':a=a*b;
		    break;
		case '/':if (b==0)
		{printf("Error!");!flag;break;
		}
			else a=a/b;
		    break;
		default:
		    break;
		}

		ch=getchar();
	}

	if(flag) printf("%d\n",a);
}
28---------------------------------
#include <stdio.h>
#include <math.h>
void main()
{
	int a,n,i,sum=0;
	int fn(int a,int n);
	
	printf("input a , n:\n");
	scanf("%d%d",&a,&n);

	for(i=1;i<=n;i++){
		sum=sum+fn(a,i);
	}

	printf("sum=%d\n",sum);
}

int fn(int a, int n)
{
	int i,res;
	for (i=1;i<=n;i++)
	{
		res=(pow(10,i)-1)/9*a;
	}
	return res;

}
29---------------------------------
#include <stdio.h>
void main()
{
	int a,countdigit(int number,int digit);
	printf("intput a number:\n");
	scanf("%d",&a);

	printf("There %d 2s in the number %d\n",countdigit(a,2),a);
}

int countdigit(int number,int digit)
{
	int res=0,t;

	while (number!=0)
	{
		t=number%10;
		if(t==digit)
			res++;
		number=number/10;
	}
	return res;
}
30---------------------------------

#include <stdio.h>
void main()
{
	int m,n,i,Fibonacci(int number);

	printf("Input m an n:\n");
	scanf("%d%d",&m,&n);

	if (n<m)
	{
		i=m;
		m=n;
		n=i;
	}
	for (i=m;i<=n;i++)
	{
		printf("%-6d",Fibonacci(i));
	}

}

int Fibonacci(int number)
{
	int res=1,a=1,b=0,i,t;

	for(i=1;i<=number;i++){
	res=a=a+b;
	t=a;
	a=b;
	b=t;}

	return res;
}
31---------------------------------
#include <stdio.h>
void main()
{
	int m,n,i,factorsum(int number);

	printf("Input m an n:\n");
	scanf("%d%d",&m,&n);

	if (n<m)
	{
		i=m;
		m=n;
		n=i;
	}
	for (i=m;i<=n;i++)
	{
		if(factorsum(i)==i)
		printf("%-6d",i);
	}

}

int factorsum(int number)
{
	int sum=0,a,i;

	for(i=2;i<number;i++){
		if (number%i==0)
			sum=sum+i;
		}
	

	return sum+1;
}

32---------------------------------
#include <stdio.h>
#include <math.h>
void main()
{
	int m,n,i,is(int number);

	printf("Input m an n:\n");
	scanf("%d%d",&m,&n);

	if (n<m)
	{
		i=m;
		m=n;
		n=i;
	}
	for (i=m;i<=n;i++)
	{
		if(is(i)==i)
		printf("%-6d",i);
	}

}

int is(int number)
{
	int sum=0;

	while (number!=0)
	{
		sum=pow(number%10,3)+sum;
		number=number/10;
	}
		

	return sum;
}
33---------------------------------
#include <stdio.h>
void main()
{
	int m,n,i,k=0,prime(int number);

	for (i=6;i<=10000;i=i+2)
	{
		for (m=2;m<=i;m++)
		{
			for (n=2;n<=i;n++)
			{
				if ((i==m+n)&&prime(m)&&prime(n))
				{
					printf("%d=%d+%d  ",i,m,n);
					k++;
					if (k%5==0)
					{
						printf("\n");
					}
					break;
				}
			}
			if(n<i) break;
		}
	}
}

int prime(int number)
{
	int l,res=1;

	for (l=2;l<=number/2;l++)
	{
		if (number%l==0)
		{
			res=0;break;
		}
	}

	return res;
}
34---------------------------------
#include <stdio.h>
void main()
{
	int n,reverse(int number);

	printf("Input a number:\n");
	scanf("%d",&n);
	printf("%d\n",reverse(n));
}

int reverse(int number)
{
	int t=0,a;
	while (number!=0)
	{
		a=number%10;
		t=t*10+a;
		number=number/10;
	}
	return t;
}