Menu: View→Interface Properties→Misc
Select the spacing of an invisible grid that objects are forced to line up with, in units of 1/96 inch. For example, if you select a snap spacing of 24, then the invisible grid will have grid lines spaced 24/96 = .25 inches apart.
Select Off if you don't want to force objects to line up with a grid.
See To force objects to line up on a grid.
Programming
In Amos Graphics programs, you can select the first item in this ComboBox as follows (Visual Basic):
Dim aComboBox As Windows.Forms.ComboBox = pd.GetComboBox("InterfacePropertiesForm", "SnapComboSnap")
aComboBox.SelectedIndex = 0