>> n=0:4;
>> h=0.8.^n;
>> x=ones(1,5);
>> y=conv(h,x)

y =

  Columns 1 through 6 

    1.0000    1.8000    2.4400    2.9520    3.3616    2.3616

  Columns 7 through 9 

    1.5616    0.9216    0.4096
>> title('the first 卷積');
>> ylabel('y');
>> xlabel('n');
>> stem(y)