Help with collision detection

I need help with my collision detection, basically i dont know how to go about it.
I'm making pacman.
I've made a 2d array, with 1's for the walls and 0's for the empty spaces I've got pacman to move but dont know how to stop him going through the walls,

im doing this for Gameboy advance using notepad++ and VisualBoy
any help would be great thanks

Code:

---

When commanded to move:
 - determine the new x/y coordinates (based on the direction of travel)
 - check those coordinates for an obstacle
 - if no obstacle, move to the new x/y coordinates
 - otherwise, don't move to the new x/y coordinates

---

I use bit-shifting to reduce the players X and Y coordinate to a value that represents a place on the tilemap...

While not C++ (GLBasic), here's a small example to muse over:-

https://dl.dropbox.com/u/3603620/CrocoGLB.zip

But, the code is a little untidy, though, you should be able to pick it apart and tidy it up to suit! :)

Dabz

EDIT: And yeah, I'm a first poster too... Hello everyone! :)