Suppose you have matrix1(N*M) and matrix2(M*L), then you can have the product using for loops as following: product=zeros(N,L); for i=1:N for j=1:L product(i,j)=matrix1(i,1)*matrix2(1,j); for k=2:M product(i,j)=product(i,j)+matrix1(i,k)*matrix2(k,j); end end end product1=product At last you can compare this product1 to the result of matrix1*matrix2 to see if they are the same (yes they are).

Well, you do show some code. Lets see how we can write it to help you out. First, understand that a matrix multiply is just a set of dot products. So we can define the (ii,jj) element of the result as just C(ii,jj) = dot(A(ii,:),B(:,jj)) Or, I could write it as: C(ii,jj) = A(ii,:)*B(:,jj); That too is a dot product, between the corresponding vectors. Unfortunately, we can't just leave it like that, as MATLAB won't understand what we are writing. We need to put loops around it, defining ii and jj using for loops. [ra,ca] = size(A); [rb,cb] = size(B); C = zeros(ra,cb); for ii= 1:ra for jj = 1:cb C(ii,jj) = dot(A(ii,:),B(:,jj)); end end Note that I preallocated C. That was important. Anyway, written as loops around a dot product, the above code will work. But really, this requires a triple set of loops, because the dot product itself can/should/might be expanded. [ra,ca] = size(A); [rb,cb] = size(B); C = zeros(ra,cb); for ii= 1:ra for jj = 1:cb % expanded: C(ii,jj) = dot(A(ii,:),B(:,jj)); for k = 1:ca C(ii,jj) = C(ii,jj) + A(ii,kk)*B(kk,jj); end end end Note that ca and rb MUST be the same for the matrices in a matrix multiply to conform for multiplication. The preallocation of C allows us to simply accumulate the results directly in place. This final form is what the code would look like, if you saw it written in (very) old school fortran, etc.