what is ip , fp registers ?

[Chandan_Gupta-r65863]

Hi

I am doing the assembly coding in ARM7TDMI and using the GNU Assembler.
In GNU ARM Assembler Quick Reference, I found 2 register Names which I 
am not able to understand, they are ip & fp.
Can anybody explain me about these registers & to which registers are 
they mapped.
what is the difference between pc & ip ?
regards
Chandan