<conio.h> is a non-standard header file, and, thankfully, you're not using anything from it, so you could leave it out.
By this point, h will be equal to MAXHOUSES, a will be MAXAUTOSALES, etc, so you'll be accessing one past the end of those arrays.
printf("Houses: %d", houses[h]);
printf("\n\nAutosales: %.2f", autosales[a]);
printf("\n\nGrades: %c", grades[g]);
But, looking at your problem:
This should solve part a):
1) Write array definitions for the following:
a) A list of 5 integer houses
b) A list of 20 double precision autoSales
c) A list of 12 characters, each representing a grade
#define MAXHOUSES 5
int houses [MAXHOUSES];