10 INPUT S
 20 DIM M(S,S)
 30 FOR I=1 TO S
 40 LET M(I,I)=1
 50 NEXT I
 60 FOR I=1 TO S
 70 SCROLL
 80 FOR J=1 TO S
 90 PRINT M(I,J);
100 NEXT J
110 PRINT
120 NEXT I