>>81題意を満たすようには作ってみたが
#include <stdio.h>
int main(void)
{
struct seiseki {
int bango;
int kokugo;
int suugaku;
int eigo;
double heikin;
char hyouka; /*評価*/
};
struct seiseki a={101,85,92,79,0.0,};
struct seiseki b,c;
printf("bango="); scanf("%d",&b.bango);
printf("kokugo=");scanf("%d",&b.kokugo);
printf("suugaku=");scanf("%d",&b.suugaku);
printf("eigo=");scanf("%d",&b.eigo);
a.heikin=((double)a.kokugo + (double)a.suugaku + (double)a.eigo)/3.0;
b.heikin=((double)b.kokugo + (double)b.suugaku + (double)b.eigo)/3.0;
if(a.heikin >= 80.0)　a.hyouka = 'G';
else a.hyouka = 'F';
if(b.heikin >= 80.0)b.hyouka = 'G';
else b.hyouka = 'F';
c.bango = b.bango+1;　c.kokugo = b.kokugo;　c.suugaku = b.suugaku;
c.eigo = b.eigo;　c.heikin = b.heikin;　c.hyouka = b.hyouka;
printf("bango heikin hyouka\n");
printf(" %3d %6.2lf %c\n",a.bango,a.heikin, a.hyouka);
printf(" %3d %6.2lf %c\n",b.bango,b.heikin, b.hyouka);
printf(" %3d %6.2lf %c\n",c.bango,c.heikin, c.hyouka);
return 0;
}