Audio Device Deleted

Good day. I am New to Apple Imac. I bought a secondhand Imac 20Inch yearly 2008 Core2Duo, 1.5gb ram and OSX10.8.5. the sound was jittering or stuttering. I don't know what I did but the next day when I restarted my Imac there was no sound and also no sound device input and output. I used onboard sound device. It showed me Intel HD. Can anyone please help?

Can anyone one help please. I'm desperate!!! Thanks.

Try:

SMC reset

and check - then try

PRAM reset
Yes, it's the same for whatever version of OS X you are running.

Thank you so much for your reply. Tried the SMC RESET and the PRAM RESET but Mac still the same. No output or input devices found.