Basically, you've tried to use a cmd designed for text files on a binary; it's not going to work and may (in your case DID) screw up your terminal settings.
Easiest thing is to logout of the terminal session and log back in.
Not sure if HP-UX has it, but there is a cmd called 'file', that will tell you about a file's format
screen.txt: ASCII text
CentOS-6.3-x86_64-bin-DVD1.iso: ISO 9660 CD-ROM filesystem data 'CentOS_6.3_Final ' (bootable)