```01:       SUBROUTINE SSCAL(N,SA,SX,INCX)
02: *     .. Scalar Arguments ..
03:       REAL SA
04:       INTEGER INCX,N
05: *     ..
06: *     .. Array Arguments ..
07:       REAL SX(*)
08: *     ..
09: *
10: *  Purpose
11: *  =======
12: *
13: *     scales a vector by a constant.
14: *     uses unrolled loops for increment equal to 1.
15: *     jack dongarra, linpack, 3/11/78.
16: *     modified 3/93 to return if incx .le. 0.
17: *     modified 12/3/93, array(1) declarations changed to array(*)
18: *
19: *
20: *     .. Local Scalars ..
21:       INTEGER I,M,MP1,NINCX
22: *     ..
23: *     .. Intrinsic Functions ..
24:       INTRINSIC MOD
25: *     ..
26:       IF (N.LE.0 .OR. INCX.LE.0) RETURN
27:       IF (INCX.EQ.1) GO TO 20
28: *
29: *        code for increment not equal to 1
30: *
31:       NINCX = N*INCX
32:       DO 10 I = 1,NINCX,INCX
33:           SX(I) = SA*SX(I)
34:    10 CONTINUE
35:       RETURN
36: *
37: *        code for increment equal to 1
38: *
39: *
40: *        clean-up loop
41: *
42:    20 M = MOD(N,5)
43:       IF (M.EQ.0) GO TO 40
44:       DO 30 I = 1,M
45:           SX(I) = SA*SX(I)
46:    30 CONTINUE
47:       IF (N.LT.5) RETURN
48:    40 MP1 = M + 1
49:       DO 50 I = MP1,N,5
50:           SX(I) = SA*SX(I)
51:           SX(I+1) = SA*SX(I+1)
52:           SX(I+2) = SA*SX(I+2)
53:           SX(I+3) = SA*SX(I+3)
54:           SX(I+4) = SA*SX(I+4)
55:    50 CONTINUE
56:       RETURN
57:       END
58: ```