C :

#include<stdio.h>

#define MAX 1000
 
int main(void)
{
    int n;
    while(scanf("%d",&n) == 1 && n >= 0)
    {
        int i,j;
        int a[MAX];      
        int p , add;          
        a[1] = 1;
        p = 1; 
        for(i = 2 ; i <= n ; ++i)  
        {
            for(j = 1 , add = 0 ; j <= p ; ++j)    
            {
                a[j] = a[j] * i + add;
                add = a[j] / 10;
                a[j] = a[j] % 10;
            }
            while(add > 0)        
            {
                a[j] = add % 10;
                add = add / 10;
                ++j;
            }
            p = j - 1;            
        }
        for(i = p ; i >= 2 ; --i)    
        {
            printf("%d",a[i]);
        }
        printf("%d\n",a[i]);
    }
    return 0;
}

C++ :

#include<stdio.h>
#include<string.h>
const int MAXN=40000;//如果是10000的阶乘，改为40000就够了 
int f[MAXN];
int main()
{
    int i,j,n;
    while(scanf("%d",&n)!=EOF)
    {
        memset(f,0,sizeof(f));
        f[0]=1;
        for(i=2;i<=n;i++)
        {
            int c=0;
            for(j=0;j<MAXN;j++)
            {
                int s=f[j]*i+c;
                f[j]=s%10;
                c=s/10;
            }    
        } 
        for(j=MAXN-1;j>=0;j--) 
           if(f[j]) break;//忽略前导0
        for(i=j;i>=0;i--)  printf("%d",f[i]);
        printf("\n");   
    }    
    return 0;
}

Pascal :

var
  i,j,n,w : longint;
  a : array[1..1000] of integer;

procedure fact(k : longint);
var
  x,i : longint;
begin
  x := 0;
  for i := 1 to w do
  begin
    a[i] := a[i]*k+x;
    x := a[i] div 10;
    a[i] := a[i] mod 10;
  end;
  while x>0 DO
  begin
    w := w+1;
    a[w] := x mod 10;
    x := x div 10;
  end;
end;

begin
  {assign(input,'ni.in');  reset(input);
  assign(output,'ni.out');  rewrite(output);}
  a[1] := 1;
  w := 1;
  readln(n);
  for i := 1 to n do fact(i);
  for j := w downto 1 do write(a[j]);
  writeln;
 { close(input);  close(output);}
end.

Java :

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

public class Main {
	public static void main(String[] args) {
		Scanner cin=new Scanner(System.in);
		int n=cin.nextInt();
		BigInteger s=BigInteger.valueOf(1);
		for (int i=1;i<=n;i++)
		{
			s=s.multiply(BigInteger.valueOf(i));
		}
		System.out.println(s.toString());
	}
}