100 PROGRAM "SpiralMa.bas"
110 TEXT 80
120 INPUT PROMPT "Enter size of matrix (max. 10): ":N
130 NUMERIC A(1 TO N,1 TO N)
140 CALL INIT(A)
150 CALL WRITE(A)
160 DEF INIT(REF T)
170   LET BCOL,BROW,COL,ROW=1:LET TCOL,TROW=N:LET DIR=0
180   FOR I=0 TO N^2-1
190     LET T(COL,ROW)=I
200     SELECT CASE DIR
210     CASE 0
220       IF ROW<TROW THEN
230         LET ROW=ROW+1
240       ELSE
250         LET DIR=1:LET COL=COL+1:LET BCOL=BCOL+1
260       END IF
270     CASE 1
280       IF COL<TCOL THEN
290         LET COL=COL+1
300       ELSE
310         LET DIR=2:LET ROW=ROW-1:LET TROW=TROW-1
320       END IF
330     CASE 2
340       IF ROW>BROW THEN
350         LET ROW=ROW-1
360       ELSE
370         LET DIR=3:LET COL=COL-1:LET TCOL=TCOL-1
380       END IF
390     CASE 3
400       IF COL>BCOL THEN
410         LET COL=COL-1
420       ELSE
430         LET DIR=0:LET ROW=ROW+1:LET BROW=BROW+1
440       END IF
450     END SELECT
460   NEXT
470 END DEF
480 DEF WRITE(REF T)
490   FOR I=LBOUND(T,1) TO UBOUND(T,1)
500     FOR J=LBOUND(T,2) TO UBOUND(T,2)
510       PRINT USING " ##":T(I,J);
520     NEXT
530     PRINT
540   NEXT
550 END DEF