SUBROUTINE SYSTEMA ( MXNA , MXWA , N , IPD , A , C )
      IMPLICIT REAL*8 ( A-H , O-Z )
      DIMENSION A(MXNA,MXWA), C(MXNA)
C------- FULL BANDWIDTH = 2 * IPD + 1
      N1 = N - 1
      IPU = IPD + 1
      NIP = N - IPD
      DO K = 1 , N1
      IP = IPD
      IF ( K .GT. NIP ) IP = N - K
      IS = K + 1
      IE = K + IP
      DO I = IS , IE
      JS = IPD - ( I - IS )
      JE = JS + IP
      P = A(I,JS) / A(K,IPU)
      IF ( P .NE. 0. ) THEN
      DO J = JS , JE
      L = J - JS + IPU
      A(I,J) = A(I,J) - P * A(K,L)
      END DO
      C(I) = C(I) - P * C(K)
      END IF
      END DO
      END DO
C------- SOLUTION OF X(N)
      C(N) = C(N) / A(N,IPU)
C------- BACK SUBSTITUTION
      JS = IPU + 1
      DO K = 1 , N1
      I = N1 - K + 1
      NI = N - I
      IF ( NI .GT. IPD ) NI = IPD
      JE = IPU + NI
      T = 0.
      DO J = JS , JE
      L = J - JS + I + 1
      T = T + A(I,J) * C(L)
      END DO
      C(I) = ( C(I) - T ) / A(I,IPU)
      END DO
      RETURN
      END