[TheSheep]

Looks like you're short a couple of brackets:

void dispgrds(int grd[], int s, int t)
{
double displaymn=mean(grd,s,t),displaystddev=stddev(grd,s    ,t); 
for (s=0; s<t; s++)
 { // Bracket!!
 if (grd[s] < displaymn - (3/2 * displaystddev))  
  cout << 'F'<<' ';
 else if (grd[s] >= displaymn - (3/2 * displaystddev) && grd[s] < displaymn - (1/2 * displaystddev)) 
  cout << 'D'<<' ';  
 else if (grd[s] >= displaymn - (1/2 * displaystddev) && grd[s] < displaymn + (1/2 * displaystddev)) 
  cout << 'C'<<' ';
 else if (grd[s] >= displaymn + (1/2 * displaystddev) && grd[s] < displaymn + (3/2 * displaystddev)) 
  cout << 'B'<<' ';
 else if (grd[s] >= displaymn + (3/2 * displaystddev))
  cout << 'A' <<' ';
 } //Bracket!!
}