>> n=0:20;
>> h=0.8.^n;
>> x=ones(1,10);
>> y=conv(h,x)

y =

  Columns 1 through 6 

    1.0000    1.8000    2.4400    2.9520    3.3616    3.6893

  Columns 7 through 12 

    3.9514    4.1611    4.3289    4.4631    3.5705    2.8564

  Columns 13 through 18 

    2.2851    1.8281    1.4625    1.1700    0.9360    0.7488

  Columns 19 through 24 

    0.5990    0.4792    0.3834    0.2975    0.2288    0.1738

  Columns 25 through 30 

    0.1298    0.0946    0.0665    0.0440    0.0259    0.0115
    >> stem(y);
>> xlabel('n');
>> ylabel('y');
>> title('the third 卷積');