iMac Problems

[KEVIN Lock]

My son (sigh) has brought his iMac slot loader 600mhz with 256mb 
memory running 10.2.8 around for resurrection.  It seems he ran out 
of memory in PhotoShop and mistakenly thought trashing the odd file 
would give more memory.

Now we have a black screen with a small LH top of screen message....sh-2.05a#

Any ideas on this one?

TIA

Kev