My mac won't turn on again, it just shows the apple logo and some code

Question

My mac was freezing up a bit while trying to get onto lanaboards.com so I decided to restart it. I figured i might as well update it at the same time. So i did that and chose the restart option that comes up when you update. It seemed like the update went through, but then it told me that it couldn't update but i was asked if i wanted to restart it, so i did. For some reason it didn't restart for a couple of minutes so i turned it off by pressing the on/off button. When i turned it back on it made the sound and then the grey background with the Apple logo appeared. Suddenly this code comes up using the word "panic" a couple of times. I'm not gonna type the whole thing cause it's kina long. It also says "Mac OS version: not yet set" (maybe cause i tried to update?) and "Kernel version: David Kernel version 12.2.1" It also says "debugger called: <panic>"
I won't be able to get it to the apple store for a week because everything closes down on thursday because of Easter and the buses seem to not go tomorrow and no one can drive me. I hope there's something i can do cause i have an important exam (100% of my grade) in two weeks so I'm freaking out a bit here. I also have some stuff due next week that just went up.
I really hope someone can help me, or at least know what may be the problem.
PS. I'm not 100% sure which operating system I have so i chose what i assume is the second newest iOS cause I know i have iOS at least
PS 2: My hard disc crashed about two months ago and was fixed at my local apple supplier, if that may have anything to do with the matter.

Answer 1

you are not in MacBook Pro forum, so might be harder to swap out and replace hard drive but  you should definitely have had them do that or even yourself.
Make sure you are at least using TimeMachine AND another backup method to clone your system drive so you always have a working 'spare' backup drive you can boot and work from - USB3 is good, TimeMachine even works decently for some on USB 2.0
Finding out why and troubleshooting a panic is a matter of trial and error after taking a look at what hardware, what software you installed (and some of which should be removed), even whether it is triggered by heat from processor or RAM (memory) errors, and memory errors can be triggered by software.
Reset SMC
http://support.apple.com/kb/HT3964
Resetting NVRAM
http://support.apple.com/kb/HT1379
Safe Mac Guide
http://www.reedcorner.net/mpg/
About Mac OS X Kernel Panics:
http://support.apple.com/kb/TS3742
Resolving Kernal Panics
http://www.thexlab.com/faqs/kernelpanics.html
http://reviews.cnet.com/8301-13727_7-10344626-263.html
http://macs.about.com/od/usingyourmac/qt/Troubleshooting-Os-X-Kernel-Panics.htm
http://support.apple.com/kb/TS3742
There’s trouble in my laptop paradise. I ended that with this caveat:
It’s much more comfortable to type on the 2011 model, with one big exception: the 2011 model runs much hotter.
I need more time to form a concrete opinion, but it seems so far that this CPU’s awesome performance definitely comes at a cost of increased heat and reduced battery life. For my intended usage as a desktop most of the time, that’s an acceptable tradeoff.
This turned out to be worse than I thought it would be, and today, the last day of my return period, I decided to return it and exchange it for a slower model.
The problem
Not only does the 2011 15” MacBook Pro run much hotter than previous generations, but as a result, the fans very frequently kick up to full speed (6200 RPM), greatly annoying anyone in the area who’s not wearing headphones.
I’ve done a lot of Google research and impromptu Twitter surveys, and this seems like a very common problem, exacerbated by a number of factors:
The quad-core i7 CPUs in the 15” run very hot, with a TDP of 45W, 10W higher than the previous dual-cores. Many people speculate that the 15” case and fan design just isn’t designed for CPUs that need this much cooling regularly.
The Core i7 CPU can use Intel’s Turbo Boost to dramatically overclock one CPU core to handle single-threaded loads whenever power and heat allow. It therefore hits its maximum TDP often when just one core is being maxed out, such as when Spotlight or Backblaze index new files, or when Time Machine is backing up.
The 2.2 and 2.3 GHz 15” models come with an AMD Radeon HD 6750M GPU, which adds significant heat. Modern 15” MacBook Pros dynamically switch between the low-powered Intel integrated GPU and the high-powered (and hot) AMD GPU as needed by applications, but the AMD GPU will always be used when an external monitor is connected — the Intel integrated GPU cannot output video over the Thunderbolt port in the 15”. (Oddly, it can in the 13” MacBook Pro and both MacBook Airs.)
It generates so much heat that it can’t be used in “clamshell mode” (closed, but with an external keyboard, mouse, and monitor attached), which has reduced airflow, without risking overheating, kernel panics, and possible long-term damage. I can’t see why Apple even enabled clamshell mode on it.
Some people report issues with the battery draining while playing a game. The 15” MacBook Pro comes with an 85W power adapter, but when stressing the CPU and GPU (such as when playing a game), the laptop draws about 93W — I don’t know enough about the electronics here to say for sure, but an insufficient power adapter capacity sounds like a plausible reason why the battery might drain under high computational load. If so, this is an embarrassing oversight by Apple.
The thermal paste seems to be very inconsistently applied, or there’s some other common manufacturing defect with the cooling system that varies per laptop. Many, many people reported having these issues and exchanging the laptop for a new one that shows far fewer issues. Many dedicated tinkerers have also reported success after reapplying the thermal compound between the CPU and heatsink, but that requires a very deep, warranty-voiding disassembly that I’m not comfortable doing. (I also haven’t owned thermal paste since 2001.)
  Put simply, it sounds like the 2011 15” MacBook Pro has a lot of manufacturing inconsistencies and defects that result in improper cooling. But it also sounds like Apple wedged far too much power draw and heat into an enclosure that’s not designed to properly cool or power these demands.  It’s not like Apple to release products like this.
But if I can get one working within my tolerances, it’s still the perfect computer for me right now. So I’m trying.
The attempted solution
Tonight, after requesting the return on my 2.3, I ordered a new, slower model that’s likely to run cooler with less fan noise. It’s the base-model 15”, but with an antiglare (matte) display added:
AMD Radeon HD 6490M: It’s manufactured on the same 40nm process as the 6750M, but has far less computational power, so I’m guessing this will result in much lower power consumption and heat.
2.0 GHz quad-core i7: This is the only CPU available with the 6490M. While I don’t expect it to be dramatically cooler-running than the 2.3 since it’s specced with the same 45W TDP, it does have a lower clock and lower Turbo Boost speeds, so I can probably expect an approximately proportional heat reduction.
So I’ll see what happens. I’m not sure what I’ll do if it doesn’t work out. This generation of 15” MacBook Pros has a lot of problems, and Apple really needs next year’s cooler-running Ivy Bridge processors as soon as possible.
http://www.marco.org/2011/09/20/heat-and-fan-issues-with-2011-15-inch-macbook-pr o