/// @@prerequisite affectations 
clear A; 
A(2,4) = 1 /// \sleftarrow{\normalfont assigns 1 to (2,4) entry of  \verb+A+}
A([1,2],[1,2])=int(5*rand(2,2)) /// \sleftarrow{\normalfont assignment {for} changing a submatrix of \verb+A+} 
A([1,2],[1,3])=[]  /// \sleftarrow{\normalfont submatrix deletion  } 
A(:,1)= 8 /// \sleftarrow{\normalfont  ``\verb+:+'' stands {for} all indices, here all the rows of \verb+A+ } 
A(:,$)=[] ///  \sleftarrow{\normalfont deletion,  ``\verb+$+'' stands {for} the last index}
A(:,$+1)=[4;5] ///  \sleftarrow{\normalfont adding a new column through assignment }