edge detection using c

[novicedude]

I am attempting to code a c program to detect edges in a 8 bit bmp images. Firstly i read the color palette into an array then take 3x3 sections of the array and multiply them with standard masks (like sobel's masks) to obtain the changed color palette values.This approach is however not working & the desired output is not shown.Could somebody help me? Novicedude