Mine

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#define N 5

struct Foititis{
	char am[10];
	char epi[20];
	char ono[20];
	float mo;
};

struct IFoititis{
	char am[10];
	int dief;
};



void selection_sort(struct IFoititis * , int);

main()
{
	struct Foititis f;
	struct IFoititis *foi , temp;
	FILE *dataf;
	FILE *indexf;
	int pl , m=0 , i , j , tm;
	int syn;
	
	dataf = fopen("Foititis.dat" , "rb+");

	if (!dataf) {
		dataf = fopen("Foititis.dat" , "wb");
		indexf = fopen("Foititis.ndx" , "wb");
		fclose(indexf);
		pl = 0;
	}
	else
	{
		indexf = fopen("Foititis.ndx" , "rb");
		fseek(indexf , 0 , SEEK_END);
		pl = ftell(indexf) / sizeof(struct IFoititis);
		fclose(indexf);
		fseek(dataf , 0 , SEEK_END);
	}

	m = pl;

	foi = malloc((pl+N) * sizeof(struct IFoititis));

	printf("\n\nEISAGOGI EGGRAFON\n\n");

	do{
		printf("\nEisagogi Aritmou Mitroou  :");
		scanf("%s", &f.am);
		printf("\nEisagogi Epithetou        :");
		scanf("%s", &f.epi);
		printf("\nEisagogi Onomatos         :");
		scanf("%s", &f.ono);
		printf("\nEisagogi Mesou Orou       :");
		scanf("%f", &f.mo);

		fwrite(&f , sizeof(struct Foititis) , 1 , dataf);

		strcpy(foi[m].am , f.am);
		foi[m].dief = m;
		m++;

		printf("\n\n Thelete nea eisagogi (1=NAI , 0=OXI) : ");
		scanf("%d" , &syn);
	} while ((syn == 1) && (m < pl+N));

	fclose(dataf);

	indexf = fopen("Foititis.ndx" , "rb+");
	fseek(indexf , 0 , SEEK_END);

	for (i=pl; i<m; i++)
		fwrite(&foi[i] , sizeof(struct IFoititis) , 1 , indexf);

	fclose(indexf);

	indexf = fopen("Foititis.ndx" , "rb");
	fseek(indexf , 0 ,SEEK_END);
	pl = ftell(indexf) / sizeof(struct IFoititis);
	fseek(indexf , 0 , SEEK_SET);
	fread(&foi[0] , sizeof(struct IFoititis) , pl , indexf);
	fclose(indexf);

	selection_sort(foi , pl);

	indexf = fopen("Foititis.ndx" , "wb");
	fwrite(&foi[0] , sizeof(struct IFoititis) , pl , indexf);
	fclose(indexf);

	free(foi);

}

void selection_sort(struct IFoititis x[] , int D)
{
	int i , j , t;
	struct IFoititis temp;

	for(i=0; i<D-1; i++) {
		t = i;
		for(j=i-1; j<D-1; j++)
			if ( strcmp(x[t].am , x[j].am)>0)
				t = j;
		temp = x[i];
		x[i] = x[t];
		x[t] = temp;
	}
}