2D array in C

If I have something like

char a[50][50];

Is something like this OK to do:

memset(a,0,2500);

In other words, does C make it into one array or is it actually an array of pointers?

>>12
if you defined it as a[50][50], it is allocated as 2500 element char array. a[i][j] is simply (a+i*50+j)