How to change logo and alter logo text in Magento

There is 2 way to change logo in Magento
1) From Admin panel
2) From core file

To change logo of magento from admin panel you need to login to admin panel . Then go to System -> Configuration -> Design
Then click on Header tab to change the logo src (source ) to your respective filename or path. There also you can change logo alt (alternet) text

TO change logo from core file you need to go app/code/core/Mage/Page/config.xml. There you can change <logo_src> to your respective file name/path. There you can change logo alt text from <logo_alt> tag.