wat is the meaning of backup?

today during lecture class, my lecturer was mentioning and craping for about 1 hour... haihz.. n i was there reading my own notes and listen to him once awhile... something caught my attention at last.. a word i used to say and talk about.. " backup "

so wat is meaning of backup ?

according to oxford dictionary, back-up means extra help or support that you get if necessary or a copy of a file, etc that can be used if the priginal is lost or damaged.

it's a word i used to mention it.. but why ? last time i used to be saying tat i need to reformat my laptop but end up 4 years i dint reformat it.. why ? cos tat time i don have any hard disk to " back - up " my files and everything.. but now i got a external hard disk but yet i still dint ' back - up' my files cos i think i don really need it !!!

there are few more " back-up " tat ppl told me.. "i donwn u to b my back- up" but at last me also the back up lak !!!

lesson of the day !!! always have a back up even thou u think u are at a safe position no matter in wat kind of things.. even in competition we need a back up players.. why not in real life right ? but this doesn't apply in some situation of course.. not every1 need a back-up cos u don need it at all !!! hahah...