Problem statement: Given a integer N, print N*N numbers in a N x N spiral

Detailed problem description: http://2600hertz.wordpress.com/2010/03/20/the-mystery-spiral/

Solution: Recently posted the following code. (managed to compress it into as few as 99 lines...)

//File  : spiral.c
//
//INPUT : Size of spiral (N)
//OUTPUT    : Numbers printed in a N x N spiral

#include <stdio.h>
#include <conio.h>
#include <stdlib.h>    

void main()
{

    int N;

    clrscr();

    //get input no. N
    printf("\nEnter size of Matrix: ");

    scanf("%d",&N);


    //Allocate reqd. memory
    int* matrix_ptr= (int*)malloc(N*N);


    //Filling the Matrix spirally

    int curr_val=N*N;
    int* curr_ptr=matrix_ptr;
    int curr_level=N;



    while(curr_level>1)
    {
        //curr_level-1 elements horizontally
        //from left to right
        for(int x=0;x<curr_level-1;x++)
        {
            *curr_ptr=curr_val;
            curr_val--;
            curr_ptr++;
        }


        //curr_level-1 elements vertically
        //from top to bottom
        for(int y=0;y<curr_level-1;y++)
        {
            *curr_ptr=curr_val;
            curr_val--;
            curr_ptr+=N;
        }


        //curr_level-1 elements horizontally
        //from right to left
        for(int z=0;z<curr_level-1;z++)
        {
            *curr_ptr=curr_val;
            curr_val--;
            curr_ptr--;
        }


        //curr_level-1 element vertically
        //from bottom to top
        for(int w=0;w<curr_level-1;w++)
        {
            *curr_ptr=curr_val;
            curr_val--;
            curr_ptr-=N;
        }


        //Next
        curr_ptr+=N+1;
        curr_level-=2;

    }


    *curr_ptr=curr_val;


    //routine to print the matrix
    printf("\n\n\n\n\n");


    for( int i=0;i<N;i++)
    {
        for( int j=0;j<N;j++)
        {
            printf("%d\t",*(matrix_ptr+(i*N+j)));
        }
        printf("\n");
    }

    getch();

}

Please comment on further optimisations (if any)...