C :

#include "stdio.h"
void F(int a[],int i,int n,int r)
{
	if(i==r)
	{
		int j;
		for(j=0;j<r;j++)
			printf("%3d",a[j]);
		printf("\n");
	}
	else
	for(a[i]=a[i-1]+1;a[i]<=n-r+i+1;a[i]++)
			F(a,i+1,n,r);
}
main()
{
	int n,r;
	int a[20];
	scanf("%d%d",&n,&r);
	if(1<n&&n<21&&1<=r&&r<=n)
		for(a[0]=1;a[0]<=n-r+1;a[0]++)
			F(a,1,n,r);
}

C++ :

#include <iostream>
#include <stdio.h>
#include <algorithm>
#include <cstring>
using namespace std;
bool is_used[30];
int n;
int r;
int a[30];
void f(int i){
	int j;
	if(i==r){
		for(j=0;j<r;j++){
			
			printf("%3d",a[j]);
		//	cout<<a[j];
		}
		printf("\n");
		return ;
	}
	for(j=a[i-1]+1;j<=n;j++){
		if(!is_used[j]){
			is_used[j]=true;
			a[i]=j;
			f(i+1);
			is_used[j]=false;
		}	
	}
}
int main()
{
	
	int i,j;
	while(scanf("%d %d",&n,&r)!=EOF){
		memset(is_used,false,sizeof(is_used));
		a[0]=0;
		f(0);
	}
	return 0;
}

Pascal :

var n,m,i:longint;
    a,b:array[0..1000] of longint;
procedure dfs(t:longint);
var i,j:longint;
begin
  if t>m then
  begin
    for i:=1 to m do write(a[i]:3);
    writeln;
    exit;
  end;
  for i:=a[t-1]+1 to n do
  begin
    a[t]:=i;
    dfs(t+1);
  end;
end;
begin
  readln(n,m);
  for i:=1 to n do
    b[i]:=0;
  dfs(1);
end.