100 INPUT "MATRIX SIZE:"; SIZE
110 GOSUB 200: REM IDENTITYMATRIX
120 FOR R = 0 TO SIZE
130 FOR C = 0 TO SIZE
140 S$ = CHR$(13)
150 IF C < SIZE THEN S$ = ""
160 PRINT MID$(STR$(IM(R, C)),1)S$;:REM MID$ STRIPS LEADING SPACES
170 NEXT C, R
180 END
190 REM *******************************
200 REM IDENTITYMATRIX SIZE%
210 SIZE = SIZE - 1
220 DIM IM(SIZE, SIZE)
230 FOR I = 0 TO SIZE
240     IM(I, I) = 1
250 NEXT I
260 RETURN