How to download sketch from arduino uno

Development Tools IDE 1.x
1

Suppose I upload some sketch on arduino unfortunately I miss any data regarding that. I also disconnect every connection ,

While I connect arduino after some time the uploaded code working nicely but I want to do some edit in code so how to get that old uploaded code back

Thanks

2

Your sketch is not there. It is compiled machine code what is uploaded into Arduino. You can download it back, but to make any changes you have to decompile it - reverse engineering. Not impossible but I guess above your skills.

3

Please give some hint for reverse engineering...

Burn Bootloader will useful in this ??

4

Please give some hint for reverse engineering...

Google.

Burn Bootloader will useful in this ??

No. Your Arduino works so what.

I think your sketch is lost, sorry. It would be better to rewrite the sketch and to backup for the next time.

5

Thanks for support...

6

It should not be a problem to download HEX from Arduino. Use the avrdude tool from the command line but be careful. Just read from the Arduino otherwise you can make it malfunctional.
It is step #1.