Update screen stuck at half way

Question

so i went to sleep listening to music off of itunes and i woke up half way through the night, looked at my computer and it was updating something and the update bar was at half way (it was the update screen where the screen is black and there is a white apple in the middle with a white and grey loading bar under it). so i went back to sleep and in the morning the bar was at the same place of about 50%, now it is 9 at night and it is still at half way.
i am running yosemite 10.10.2 (i think) on a 13 inch 2014 macbook air
i have tried rebooting numerous times but when i turn the computer back on it resumes the update
please help i need this fixed asap since i use this computer for work, is their any way that i could boot strait into the desktop to bypass the update or something?
btw i just found the image on google images mine is obviously at about 50%
thanks in advance

Answer 1

You did shutdown by holding the power button until the mac shutoff I assume.
If this happens when starting up it looks as if a system update download was made (and these are installed while restarting); so this means the startup procedure was stopped for some reason.
Try following: shutdown again, the startup while holding CMD+R: it starts (slow) in the Recovery partition: choose "Install OSX", this will take some time, depending on the internet speed. This will leave non-system elements unchanged.