Everything below was written with bitcoin core in mind since its the only wallet I know that uses files called "wallet.dat"
File -> Backup
20 BTC course, because bitcoin you go online and recorded in the data base of your wallet. because bitcoin does not go into your pc, but to your wallet. Thank you
No, no, no. Stop posting bullshit for a few satoshi.
#1 "bitcoin does not go into your pc, but to your wallet"
OP is talking about a local wallet, namely bitcoin core as indicated by the wallet.dat filename. Thus, the crucial private keys are stored in the wallet file, which is not "online".
#2 The correct answer is not "20 BTC (of) course", but maybe 20 BTC maybe 15 BTC.
Bitcoin core - by default - keeps up to 100 private keys pregenerated and hidden from the user. If the 5 BTC have been received on an address that was generated with the private key 101 after the last backup (or any later key), the answer is 15 BTC. If the 5 BTC have been received on an address that can be generated with one of these 100 private keys, the answer is 20 BTC. Bitcoin core requires periodical backups, as the pool of private keys still covered by the last one constantly decrease, e.g. due to change addresses or new receiving addresses.
how to backup a wallet data?
File -> Backup
Hi guys 
not new there but can't remember my nickname nor my registration email.
Simple question:
Let's say Monday I have 15 btc. Monday night I backup my wallet.dat on an external drive.
Thursday I get 5 more btc, so total btc on my wallet = 20.
Wednesday my computer crashes, I reinstall Windows, then Bitcoin-qt, then put back the wallet.dat I backed up on Monday.
Will I have 20 btc or only 15?
This happened for real and I'm not sure I got back all my coins :<
not new there but can't remember my nickname nor my registration email.Simple question:
Let's say Monday I have 15 btc. Monday night I backup my wallet.dat on an external drive.
Thursday I get 5 more btc, so total btc on my wallet = 20.
Wednesday my computer crashes, I reinstall Windows, then Bitcoin-qt, then put back the wallet.dat I backed up on Monday.
Will I have 20 btc or only 15?
This happened for real and I'm not sure I got back all my coins :<
20 BTC course, because bitcoin you go online and recorded in the data base of your wallet. because bitcoin does not go into your pc, but to your wallet. Thank you
No, no, no. Stop posting bullshit for a few satoshi.
#1 "bitcoin does not go into your pc, but to your wallet"
OP is talking about a local wallet, namely bitcoin core as indicated by the wallet.dat filename. Thus, the crucial private keys are stored in the wallet file, which is not "online".
#2 The correct answer is not "20 BTC (of) course", but maybe 20 BTC maybe 15 BTC.
Bitcoin core - by default - keeps up to 100 private keys pregenerated and hidden from the user. If the 5 BTC have been received on an address that was generated with the private key 101 after the last backup (or any later key), the answer is 15 BTC. If the 5 BTC have been received on an address that can be generated with one of these 100 private keys, the answer is 20 BTC. Bitcoin core requires periodical backups, as the pool of private keys still covered by the last one constantly decrease, e.g. due to change addresses or new receiving addresses.
Should also mention that you want to store your wallet (and most importantly encrypt it!) in a safe place. Stolen wallet + encryption key = bye bye bitcoins
