C :

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


int main()
{
   int n,p,sum=0; 
   unsigned int i=0,j,k=0,l=0;
   char m[30],a[2],b[2],res[1000],ch;
   memset(res,0,sizeof(res));
   scanf("%s",m);
   for(i=strlen(m)-1;i>=0;i--)
   {
       if(m[i]!='>')
	   {
		   a[k]=m[i];
		   k++;
	   }
	   else
		   break;
   }
   a[k]='\0';
   if(k==1)
	   p=a[0]-'0';
   else
	   p=a[0]-'0'+(a[1]-'0')*10;
   for(i=strlen(m)-2-k;i>=0;i--)
   {
       
       if(m[i]!='<')
	   {
		   b[l]=m[i];
		   l++;
	   }
	   else
		   break; 
   }
   b[l]='\0';
   if(l==1)
	   n=b[0]-'0';
   else
	   n=b[0]-'0'+(b[1]-'0')*10;
   m[strlen(m)-k-l-2]='\0';
   for(i=0;i<strlen(m);i++)
   {
       sum=sum*n+m[i]-'0';
   }
   while(sum)
   {
   
	   res[i]=sum%p+'0';
	   sum/=p;
	   i++;
   }
   res[i]='\0';
   for(j=0,--i;j<i;i--,j++)
   {
     ch=res[j];
	 res[j]=res[i];
	 res[i]=ch;
   }
   if(strlen(m)==0)
	   strcmp(res,"0");
   printf("%s<%d>=%s<%d>",m,n,res,p);
   return 0;
}

C++ :

#include <iostream>
#include <string.h>
#include <stack>
#include <queue>
using namespace std;
int main()
{
	char T[30];
	cin>>T;
	queue <int> Q;
	int ans=0,n=0,p=0;
	stack <int> S;
	int len=strlen(T);
	int i=0;
	while(T[i]>='0'&&T[i]<='9')
			Q.push(T[i++]-'0');
	i++;
	while(T[i]>='0'&&T[i]<='9')
			n=n*10+T[i++]-'0';
	i++;
	while(T[i]>='0'&&T[i]<='9'&&i<len)
			p=p*10+T[i++]-'0';
	while(!Q.empty())
	{
		ans=ans*n+Q.front();
		cout<<Q.front();
		Q.pop();
	}
	while(ans)
	{
		S.push(ans%p);
		ans/=p;
	}
	cout<<"<"<<n<<">=";
	while(!S.empty())
	{
		cout<<S.top();
		S.pop();
	}
	cout<<"<"<<p<<">"<<endl;
	return 0;
}

Pascal :

var s,strm,strm1,strn:string;x,y,i,j:longint;n,m,m1,w:int64;
    z:array[1..10000]of integer;
begin
  readln(s);
  x:=pos('<',s);
  for i:=1 to x-1 do strn:=strn+s[i];
  y:=pos('>',s);
  for i:=x+1 to y-1 do strm:=strm+s[i];
  val(strm,m);
  for i:=y+1 to length(s) do strm1:=strm1+s[i];
  val(strm1,m1);
  w:=1;
  for i:=length(strn) downto 1 do
    begin
      n:=n+(ord(strn[i])-48)*w;
      w:=w*m;
    end;
  i:=0;
  repeat
    i:=i+1;
    z[i]:=n mod m1;
    n:=n div m1;
  until n=0;
  write(strn,'<',strm,'>=');
  for j:=i downto 1 do write(z[j]);
  writeln('<',m1,'>');
end.

Java :

import java.math.BigDecimal;
import java.util.Scanner;

public class Main {
	public static String str;
	public static int n, m;
 
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		str = sc.next();
		int ids = str.indexOf("<");
		String tmp = str.substring(ids);
		char[] tm = tmp.toCharArray();
		String num = "";
 
		for (int i = 0; i < tm.length; i++) {
			if (tm[i] >= '0' && tm[i] <= '9') {
				num += tm[i];
			}
			if (tm[i] == '>') {
				n = Integer.parseInt(num);
				num = "";
			}
		}
		m = Integer.parseInt(num);
		// System.out.println(n + " " + m);
		// 左边的数字
		str = str.substring(0, ids);
		BigDecimal result = new BigDecimal("0");
		// n进制底数
		BigDecimal ndis = new BigDecimal("" + n);
		// 假如进制不是10进制，则转化为十进制
		if (n != 10) {
			char[] nums = str.toCharArray();
			for (int i = nums.length - 1; i >= 0; i--) {
				result = result.add(new BigDecimal(nums[i] + "").multiply(ndis
						.pow(nums.length - 1 - i)));
				// System.out.println(result + " ");
				// result += Math.pow(n, nums.length - 1 - i);
			}
		} else { // 进制是10进制
			result = new BigDecimal(str);
		}
		// 转化为m进制
		if (n == m) {
			System.out
					.println(result + "<" + n + ">=" + result + "<" + m + ">");
		} else {
			long yus;
			String mizji = "";
			// m进制底数
			BigDecimal mdis = new BigDecimal("" + m);
			while (result.compareTo(new BigDecimal("0")) > 0) {
				mizji = result.remainder(mdis) + mizji;
				result = result.divide(mdis, BigDecimal.ROUND_DOWN);
			}
			System.out.println(str + "<" + n + ">=" + mizji + "<" + m + ">");
		}
 
	}
}