100 INPUT "MATRIX SIZE:"; SIZE%
110 GOSUB 200"IDENTITYMATRIX
120 FOR R = 0 TO SIZE%
130     FOR C = 0 TO SIZE%
140         LET S$ = CHR$(13)
150         IF C < SIZE% THEN S$ = " "
160         PRINT IM(R, C) S$; : NEXT C, R
170 END

200 REMIDENTITYMATRIX SIZE%
210 LET SIZE% = SIZE% - 1
220 DIM IM(SIZE%, SIZE%)
230 FOR I = 0 TO SIZE%
240     LET IM(I, I) = 1 : NEXT I
250 RETURN :IM