The FORTRAN level-2 BLAS call for this operation is

SUBROUTINE SYMV ( UPLO, N, ALPHA, A, LDA, X, INCX, BETA, Y, INCY )

Here is replaced by S, D, C, or Z
to indicate the datatype of the data (single, double, complex, double precision complex).
Parameter UPLO indicates whether A is stored in the
upper (UPLO = "Upper") or lower (UPLO = "Lower") triangular portion of array A.
Parameter N holds the matrix dimension
n .
Parameters ALPHA and BETA hold the scaling factors
and . Parameters A, X, and Y equal the
addresses of where matrix A and vectors x and y start in
memory. The leading dimension of the matrix is given in
LDA and the strides for the vectors in INCX and INCY.