How can I do the correlation using loops?

I have to find the correlation of x and y with the help of loops.

x= [ 1 2 3 4]

y= [ 2 3 5 6]

Functions such as xcorr and corr will not be used. Thank you in advance for your help

[Rik]

You can find guidelines for posting homework on this forum here. If you have trouble with Matlab basics you may consider doing the Onramp tutorial (which is provided for free by Mathworks).