CS6 not changing photo size?

Question

I have watched a few videos, on changing image size, in cs6, since when I tried it, the photo didn't change size at all. I could change it to 1 million inches tall, and it will stay the same size. I don't really know what to do. I've tried unlocking the default layer, and changing the canvas size and nothing seems to make this image change size. I want the image in the picture bigger,  am I even doing it right by going under image, and changing the image size, and hitting ok? That is all the tutorials say to do, yet nothing happens for my image.

Answer 1

An image file just stores the image as arrays of pixels -- 1000 x 2000, 3000 x 4000, 5723 x 8557 or whatever.  Those pixel maps don't have any inherent "size".  The image file can also contain metadata that tells software how to interpret the pixels.  For example, the metadata could say 72 pixels per inch (ppi), 100 ppi, 360 ppi, 1000 ppi, or whatever. 
In Photoshop (and in most other pixel image editing programs), you can change the metadata to give the image a different "size" without changing the pixels at all.  For example, an image that's 1000 x 2000 pixels, at 100 ppi, will be 10" x 20".  If the ppi is changed to 1000 ppi, the same image will be 1" x 2".  And at 10 ppi, the image will be 100" x 200".  But the image pixels will be unchanged; they will just be bigger or smaller pixels.  Each one of these files will be 2 megapixels and will occupy exactly the same amount of file space (before compression, assuming 8-bit RGB, 6 MB).
All of the foregoing is with "resample image" unchecked, which ensures no change to the pixel array data.  Now, if you want to grow (or shrink) the size of the image pixel array, you can do that in photoshop by changing the size with "resample image" checked.  This will add or subtract pixels, changing the image data.  So if you change a 1000 x 2000 image that's 100 ppi and thus 10" x 20", by changing the image size to 1" x 2", with resampling checked, the data will be shrunk to give you a 100 x 200 image.  90% of the data will disappear.  Your image will be 1/10 the size in terms of data and pre-compression file size.  If you were to resize the image back to 10" x 20" with resampling unchecked, you would still have a 100 x 200 image, which would have 10 ppi resolution --  a much crappier image.  If you were to resize the image back to 10" x 20" with resampling checked, you would get a 1000 x 2000 image with 100 ppi resolution, but it would still be a crappy image because 90% of the pixels would be newly created through interpolation, not the pixels in the original image.