Cisco && Magic Question Mark (?)
In Cisco IOS, Every mode (user mode, privileged mode etc) has help system built in. You can use the magic question mark (?) in user mode as well as in sub-configuration mode.
What if you want to use question mark (?) in description or aspath-regex. :)
Well, to write a question mark in IOS, the escape sequence CTRL-V or ESC-Q must be entered first, otherwise the IOS parser will interpret the question mark as an attempt to invoke the context sensitive help.
JAHIL#conf t
Enter configuration commands, one per line. End with CNTL/Z.
JAHIL(config)#int
JAHIL(config)#interface gi3/0/0
JAHIL(config-if)#des
JAHIL(config-if)#description ?
LINE Up to 240 characters describing this interface
JAHIL(config-if)#description
You see, when you write ? this will bring you to the help menu. What if you really want to write description along with ?. You can use CTRL-V or ESC-Q.
JAHIL#conf t
Enter configuration commands, one per line. End with CNTL/Z.
JAHIL(config)#int
JAHIL(config)#interface gi3/0/0
JAHIL(config-if)#des
JAHIL(config-if)#description (now press CTRL-V or ESC-Q)
JAHIL(config-if)#description ?IGotIt (oh it worked)
You can use CTRL-V or ESC-Q whenever or wherever it's needed :)