write/append in my own exe with c programming

How can I append my own exe to upgrade it with c programming. I have tried to use append mode in exe but helpless with it. Any way to modify any 开发者_开发百科exe? There are simpler process for .txt but none for .exe.

I want to add the codes or join the functions just like any program updates.

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It's not that simple. You can't (simply) add code to the end of an .exe file to modify it; there are internal indexes, tables, etc.

For software update you need to replace the file in question with a newer versions. There are frameworks for doing that in an easy and automated way. If you tell is what language and environment you are using, someone is sure to recommend a good software update solution.