for the given signal h(n), is it 1 for n=0:149 or the n's of each is a different thing?
The n's represent samples because you are working with discrete signals. They are not all 1. For n=0:149 every sample is incremented by 1.If you write n=0:149 in MATLAB you will get a vector 1x150 with elements 0,1,2,3.....149. I recommend the book Digital Signal Processing Using MATLAB by Vinay K. Ingle and John G. Proakis
n = 0:149; %n = [0,1,2,3...149] h = 3*(0.5).^n.*(stepfun(n,0)-stepfun(n,100))-2*(1/3).^n.*(stepfun(n,0)-stepfun(n,50)); x = stepfun(n,0)-stepfun(n,70); y = conv(h,x); stem(y);