bgno = argument0
for (i = 0; i < bgno; i += 1)
{
    bgid[i] = 0
    xoff[i] = 0
    yoff[i] = 0
    xratio[i] = 1
    yratio[i] = 1
    xscale[i] = 1
    yscale[i] = 1
    alpha[i] = 1
    tile[i] = 1
}