C言語の定数にはどのような種類があるのでしょうか?

const datatype variable;

#include<stdio.h>
int main(){
   const int height=20;
   const int base=40;
   float area;
   area=0.5 * height*base;
   printf("The area of triangle :%f", area);
   return 0;
}

The area of triangle :400.000000

include<stdio.h>
void main(){
   int a;
   int *p;
   a=10;
   p=&a;
   printf("a=%d</p><p>",a);//10//
   printf("p=%d</p><p>",p);//address value of p//
   *p=12;
   printf("a=%d</p><p>",a);//12//
   printf("p=%d</p><p>",p);//address value of p//
}

a=10
p=6422036
a=12
p=6422036