Using Microsoft Sharepoint APIs we can easily Add, Update and Delete list items programmatically. Provided below is a code snippet in C# .Net demonstrating all the three operations..

using (SPSite oSPsite = new SPSite("http://website url/"))
{
using (SPWeb oSPWeb = oSPsite.OpenWeb())
      {
            oSPWeb.AllowUnsafeUpdates = true;
 
            // Fetch the List
            SPList list = oSPWeb.Lists["MyList"];
                   
            //Add a new item in the List
            SPListItem itemToAdd = list.Items.Add();
            itemToAdd["Title"] = "Test Title";
            itemToAdd["Description"] = "Test Description";
            itemToAdd.Update();
 
            // Get the Item ID
            listItemId = itemToAdd.ID;
 
            // Update the List item by ID
            SPListItem itemToUpdate = list.GetItemById(listItemId);
            itemToUpdate["Description"] = "Changed Description";
            itemToUpdate.Update();
 
            // Delete List item
            SPListItem itemToDelete = list.GetItemById(listItemId);
            itemToDelete.Delete();
 
            oSPWeb.AllowUnsafeUpdates = false;
       }
}