when i run the line
ruby script/generate scaffold Item Manage
it displays: wrong number of arguments(1 for 2)
i am consulting book "biggining Ruby on Rails" pg 167 where controler and model are created together. kindly give your suggestion.
As far as I know, the boot you're reading is based on Rails 1.2. If your installation is Rails 2.x the scaffold generator will be different. With the scaffold generator now, you can create a scaffold for a model, the controller will get the default name (pluralize of the model). You can add the column names to your scaffold command directly. So
ruby script/generate scaffold Item name:string price:decimal description:text
will generate a model Item, a database table "items" with the columns name, price and description, a controller "ItemsController" containing the basic CRUD actions and the views for the CRUD actions. Plus the route "map.resources items" that lets you access all the actions of the controller.
Note that using the scaffold generator is usually only done to quickly
start doing stuff in your application and you will always want to
change the default templates and actions for a real life application.
You can always change the name of controller to "Manage" for
separating the admin-only actions (for managing Items) from user-only
actions (for displaying, searching and buying Items for example).
That's hand work and if you do that, you will be rewarded with
learning how Rails routing works 
Good luck!
Dirk.
also, you can drop the capital letter in item:
ruby scrip/generate item (always always singular!!)