отсортировать студентов по возрасту

#include<stdio.h>
#include <iostream>
#include<stdlib.h>
#include<conio.h>
#include<string.h>
#include<process.h>
struct person {
char FIO[100];
int age[10];
float reiting;
 
};
void initStruct(char *fileName, int n)
{
int i;
FILE *fin;
struct person a;
 
system("cls");
fin = fopen(fileName, "w");
if(!fin)
{
printf("Error: can't open file: %s\n", fileName);
system("pause");
exit(1);
}
 
for(i=0; i<n; i++)
{
printf("\n Imya, vozrost, reiting\n");
scanf("%s", a.FIO);
fprintf(fin,"%s ", a.FIO);
scanf("%s", a.age);
fprintf(fin,"%s ", a.age);
scanf("%f", &a.reiting);
fprintf(fin,"%f ", a.reiting);
}
fclose(fin);
system("pause");
}
 
void showStruct(char *fileName)
{
FILE *fin;
struct person a;
 
system("cls");
fin = fopen(fileName, "r");
if(!fin)
{
printf("Error: can't open file: %s\n", fileName);
system("pause");
exit(1);
}
printf("|-------------------------------------------------|\n");
printf("| FIO | Vozrost|Reiting|\n");
printf("|--------------+--------------------------+-------|\n");
while(!feof(fin))
{
fscanf(fin,"%s", a.FIO);
printf("|%14s|", a.FIO);
fscanf(fin,"%s ", a.age);
printf("%26s|", a.age);
fscanf(fin,"%f ", &a.reiting);
printf("%7f|\n", a.reiting);
}
fclose(fin);
printf("|-------------------------------------------------|\n");
system("pause");
}
 
void add(char* fileName, int n)
{
int i;
FILE *fin;
struct person a;
 
system("cls");
fin = fopen(fileName, "a");
if(!fin)
{
printf("Error: can't open file: %s\n", fileName);
system("pause");
exit(1);
}
 
for(i=0; i<n; i++)
{
printf("\n Imya, adress, vozrost\n");
scanf("%s", a.FIO);
fprintf(fin,"%s ",a.FIO);
scanf("%s", a.age);
fprintf(fin,"%s ",a.age);
scanf("%f", &a.reiting);
fprintf(fin,"%f ",a.reiting);
}
fclose(fin); 
system("pause");
}
 
void del(char *fileName)
{
FILE *fin, *temp;
struct person a;
char name [20];
 
system("cls");
printf("vvedite imya: ");
scanf("%s",name);
fin = fopen(fileName, "r");
if(!fin)
{
printf("Error: can't open file: %s\n", fileName);
system("pause");
exit(1);
}
temp=fopen("temp","w");
if(!temp)
{
printf("Error.\n");
system("pause");
exit(1);
}
 
while(!feof(fin))
{
fscanf(fin,"%s ", a.FIO);
fscanf(fin,"%s ", a.age);
fscanf(fin,"%f ", &a.reiting);
if(strcmp(name, a.FIO) == 0)
{
printf("%s ", a.FIO);
printf("%s ", a.age);
printf("%f\n", a.reiting);
}
else
{
fprintf(temp,"%s ",a.FIO);
fprintf(temp,"%s ",a.age);
fprintf(temp,"%f ",a.reiting);
}
}
fclose(fin);
fclose(temp);
remove(fileName);
rename("temp", fileName);
system("pause");
}
 
void zapros(char *fileName,  int kol)
{
int i;
FILE *fin;
struct person a;
 
system("cls");
fin = fopen(fileName, "r");
if(!fin)
{
printf("Error: can't open file: %s\n", fileName);
system("pause");
exit(1);
}
printf("\nPersona: \n");
printf("|-------------------------------------------------|\n");
printf("| FIO |Vozrost|Reiting|\n");
printf("|--------------+--------------------------+-------|\n");
while(!feof(fin))
{
fscanf(fin,"%s ", a.FIO);
fscanf(fin,"%s ", a.age);
fscanf(fin,"%2.2f ", &a.reiting);
if(a.age[i]>kol)
{
printf("|%14s|", a.FIO);
printf("%26s|", a.age);
printf("%7.2f|\n", a.reiting);
printf("|-------------------------------------------------|\n");
}
}
fclose(fin);
system("pause");
}
 
 
int main()
{
int n, k;
int kol;
setlocale(LC_ALL,"Russian");
do
{
system("cls");
printf("\n1: Sozdat stryktyry. ");
printf("\n2: dobavit. ");
printf("\n3: pokazat stryktyry. ");
printf("\n4: ydalit zapis. ");
printf("\n5: Âûáðàòü");
printf("\n6: vychod. \n");
scanf("%d",&k);
switch(k)
{
case 1:
printf("Kolichestvo zapisei: ");
scanf("%d",&n);
initStruct("D://ou.txt", n);
break;
case 2:
printf("Kolichestvo zapisei: ");
scanf("%d",&n);
add("D://ou.txt", n);
break;
case 3:
showStruct("D://ou.txt");
break;
case 4:
del("D://ou.txt");
break;
case 5:
printf("Kolichestvo zapisei: ");
scanf("%d",&kol);
zapros("D://ou.txt", kol);
break;
case 6:
exit(0);
default:
printf("Vvedite 1, 2 ili 3 4 5 6.");
break;
}
}while(1);
}