anyone who tell me about this?

[syjeon]

sometime, I so confused between the boot image and ios image.

What is the different about this?

compare with window 95,98 base dos ver 7.0

boot image is similar the pc's dos and ios is pc's MS window?.

[rsissons]

The boot image is simply a cut down version of IOS in order to fit onto the onboard flash. Its only purpose is to enable you to load the complete IOS if, for some reason, the running IOS gets corrupted in some way.

Because not all IOS functions are supported, if you save a running configuration from the boot image, you may lose some of the config. Most significantly, routing is not supported so, if you are attempting to load an IOS image from a TFTP server which is not on a directly attached subnet, you will need to add the 'ip default-gateway ...' command to the running config.

[thisisshanky]

Here is a Cisco definition of Boot image

The boot image is a subset of the Cisco IOS® software that is used to download main Cisco IOS software images to the router using TFTP in recovery situations. The user can interact with this image through a command line interface signified by the prompt Router(boot)#. Some platforms (Cisco 1600, 2500) have it in ROM; others (high-end routers) have it in bootflash. Depending on your platform, this image may be called xboot image, rxboot image, bootstrap image, or boot loader or helper