Cisco IOS (Internetwork Operating System) is the Operating System software used on Cisco routers and current Cisco Network Switches. Cisco IOS (Internetwork Operating System) image file is normally stored in flash memory and it has a naming convention.

Following output shows the "show-flash" command from privileged mode.

OmniSecu03#show flash

System flash directory:
File  Length   Name/status
  3   5571584  c2600-i-mz.122-28.bin
  2   28282    sigdef-category.xml
  1   227537   sigdef-default.xml
[5827403 bytes used, 58188981 available, 64016384 total]
63488K bytes of processor board System flash (Read/Write)

• The name of the Cisco IOS (Internetwork Operating System) file is "c2600-i-mz.122-28.bin".

• The "c2600" means that this is a 2600 series router.

• The "i" indicates  that this is the IP routing version of the IOS.

• The "mz" indicates that this version of the IOS runs from RAM and is compressed.

• The "122-28" indicates that this is IOS version 12.2, patch level 28.