代码什么意思

cetc41

>> subplot(311);
>> n=0:1:7;
>> y=[1,1,1,-1,1,-1,-1,1];
>> stem(n,y) ;
>> axis([ -1 8 -1.5 1.5]);
>> subplot(312);
>> axis([ -1 8 -1.5 1.5]);
>> arrow([0,0],[0,1]);
>> arrow([1,0],[1,1]);
>> arrow([2,0],[2,1]);
>> arrow([3,0],[3,-1]);
>> arrow([4,0],[4,1]);
>> arrow([5,0],[5,-1]);