How can I backup my programs/applications, so that after I format my Linux and install a new one, I can still use the backup-ed ones?

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http://askubuntu.com – Something that's been bothering me for a while, is the loss of all my installed programs in Linux after I format it. You know, whenever I format my Windows machine, there's a folder, full-fetched with an army of gigs of programs, basically EVERYTHING you need after a format, so I just install the stuff I need, takes about 10 mins, not that much time. But in Linux, it's a headache actually, when I format it, I lose most if not all what I had installed. Is there a way, that I could backup all my programs, all apps, put them in a directory or something, so that I could install them quickly next (HowTos)