When I wanna buy a computer, I decide to buy second hand computer. It means that the computer is used by someone else before. Just because I have no enough money to buy a new one. One week left, in the middle of the night, I sit down on chair in front of my desk with my second hand computer that I have bought. I try it all day long. I explore inside drive C, D, and E.

There are a lot of files I found. JPG as I know is File Extension of an image. DOC as I know is a file extension of MS word document. But, one hours left, I found a file extension that I have no idea what it is. That was File Extension jad. Then I click twice to that file. No program detected. Oh my god, I feel curious. So, I type keyword “jad” on search engine, I found the answer. jad is a file extension of java application from Sun Microsystems, Inc.

Another day, I borrow my friend’s flash disc to copying his paper. When I explore inside his flash disc, I found another file extension that makes me confuse and curious. That was file extension dmg. When I wanna call him, his cellular phone is inactive, so as usual, I search to search engine. Yes, finally I’ve got the answer. file extension dmg is a disk image file. This file, can be used to burn CD’s or DVD’s. If you wanna try to open this file, you can open it by Apple disk utilities.