Write a program that checks the initial value in memory location x4000 to see if it is a valid ascii code and if it is a valid ascii code,

You must dereference it as an unsigned char * to get a byte, then check if it is in the valid ASCII range of 32-127.

void * ptr = 0x4000;

unsigned char c = * (unsigned char*) ptr;

if ((c>=32) && (c<=127))

{

/ / Valid ascii

}

else

{

/ / Not ascii

}