Fortran arrays argument

I'm trying to convert a Fortran code to VBA, with very little knowledge of Fortran.

what does P(I,1) stand for? Or P(1,J)? It is supposed to represent a scalar vector.

DO 25 J=1,NF
        DO 25 I=1,J
          CALL INPR(P(I,1),P(J,1),C(I,J),NF,NF,NF)
25        C(J,I)=C(I,J)

    C CALLED FROM MANY SUBROUTINES

       subroutine INPR (a, b, c, ia, ib, n)
c
c Caclulates the scalar product between two vectors
c
c   a   - input array
c   b   - input array
c   c   - output scalar product
c   ia  - input stride factor for array a
c   ib  - input stride factor for array b
c   n   - input number of elements
c
       dimension a(*), b(*)
       c = 0.0
       ipa = 1
       ipb = 1
       do 10 i = 1, n
           c = c + a(ipa) * b(ipb)
           ipa = ipa + ia
  10       ipb = ipb + ib
       return
       end