function [sys] = vol_1(vol,%beta,spgr)

    // Output variables initialisation (not found in input variables)
    sys=[];

    // Display mode
    mode(0);

    // Display warning for floating point exception
    ieee(1);

    // VOL1.Building block for a volume having two flow inputs.
    //  Author:D. A. Gutz
    //  Written:16-Apr-92
    //  Revisions:None.

    //  Input:
    //  betaFluid bulk modulus, psi.
    //  spgrFluid specific gravity.
    //  volVolume, cuin.
    //  wfsInput # 1, supply flow, pph.
    //  wfdInput # 2, discharge flow, pph.

    //  Output:
    //  sysPacked system of Input and Output
    //  pOutput # 1, volume pressure, psia.

    // 

    //  Derivative
    dp = ((%beta/129.93948)/vol)/spgr;// Derivative, psi/sec.
    a = 0;
    b = [dp, -dp];
    c = 1;
    e = 0;

    //  Form the system.
    sys = pack_ss(a, b, c, e);

endfunction
