difficult vs. hard

Hello everybody.

What’s the difference between ‘hard’ and ’ difficult’?

Could we use ‘harder’ instead of ‘more difficult’ in the following sentence?

I was suprised how easy it was to use the computer. I thought it would be more difficult.

Thank you very much.

In that sense, ‘hard’ and ‘difficult’ are synonyms and can be used interchangeably.

‘Hard’ obviously has the additional meaning of being very firm, which cannot be substituted with difficult.

Thank you for your soon answer.

Is there rules when we use ‘difficult’ or ‘hard’?

Is it depend on sentence meaning?

As I said,‘difficult’ can almost always be replaced by ‘hard’.

‘Hard’ has other meanings so cannot always be replaced by ‘difficult’.

Thank you for your answer.