C++ :

#include<iostream>
using namespace std;
int main()
{
	int t;  //t:统计已输出字符个数 
	t=0;
	for (char c='a';c<='z';c++)   //顺序输出 
	{
		cout<<c;
		t++;
		if (t%13==0) cout<<endl;  //每输出13个字符换行 
	}
	t=0;
	for (char c='z';c>='a';c--)   //倒序输出 
	{
		cout<<c;
		t++;
		if (t%13==0)cout<<endl;   
	}
	return 0;
}

Pascal :

program aa;
begin
 writeln('abcdefghijklm');
 writeln('nopqrstuvwxyz');
 writeln('zyxwvutsrqpon');
write('mlkjihgfedcba');
end.

Java :

class Main {
	public static void main(String[] args) {
			for(int k=97;k<=109;k++){
				System.out.print((char)(k));
			}
			System.out.println();
			for(int j=110;j<=122;j++){
				System.out.print((char)(j));
			}
			System.out.println();
			for(int j=122;j>=110;j--){
				System.out.print((char)(j));
			}
			System.out.println();
			for(int j=109;j>=97;j--){
				System.out.print((char)(j));
			}
		}

}