I like to know that should i code on my codeblock(gcc) or on online jugde during ongoing short contest.
Although i code on my pc either it is long or short and sometimes it comsumes more time in compiling and checking for diffrent test cases…what should be the preferred option if it is online judge than give some links for good judges…
You may code on codeblocks, i like its interface, and for running code you may use ideone.com using visibility as private so that no one can see your code. hackerRank also provide online judge for testing your codes…
Although you may use file handling too for offline debugging and running your code on various test cases…
Also for keeping visibility private you can read this thread: http://discuss.codechef.com/questions/58134/how-to-not-left-a-code-as-public
Now its up to you… Take a wise decision… 
I find it convenient to code on my local environment because of all the templates and headers I use. You can use an online compiler, however. I like to use online compilers only when testing my program with different test cases, as you can just type them in the Input area or even copy them in.