#include<stdio.h>
typedef struct talmid{
int code;
double age;
}std1;
void bulidStudentFile(char *s);
void printstudentFile(char *s);
double AvgAge(char *s);
void SortFile(char *s, char *nf);
void main()
{
	int run;
	char fname[30]="nbinf.bin";
	char sortfname[30]="nbinf.bin";
	double avg;
	bulidStudentFile(fname);
	printstudentFile(fname);
	avg=AvgAge(fname);
	printf("avg=%lf", avg);
	SortFile(fname, sortfname);
	printstudentFile(sortfname);
	scanf("%d", &run);
}
void bulidStudentFile(char *s)
{
	int i, n;
	std1 talmid;
	FILE *fp;
	if((fp=fopen(s, "wb"))!=NULL)
	{
		printf("enter num of students \n");
		scanf("%d", &n);
		for(i=0; i<n ; i++)
		{
			printf("\n enter code and age \n");
			scanf("%d", &(talmid.code));
			scanf("%lf", &(talmid.age));
			fwrite(&talmid, sizeof(std1), 1, fp);
		}
		fclose(fp);
	}
}
void printstudentFile(char *s)
{
	FILE *fp;
	std1 talmid;
	if((fp=fopen(s, "rb"))!=NULL)
	{
		fread(&talmid, sizeof(std1), 1, fp);
		while(!feof(fp))
		{
			printf("\n code=%d \n", talmid.code);
			printf("age=%lf \n", talmid.age);
			fread(&talmid, sizeof(std1), 1, fp);
		}
		fclose(fp);
	}
}
double AvgAge(char *s)
{
	double avg=0;
	int count=0;
	FILE *fp;
	std1 talmid;
	if((fp=fopen(s, "rb"))!=NULL)
	{
		fread(&talmid, sizeof(std1), 1, fp);
		while(!feof(fp))
		{
			avg+=talmid.age;
			count++;
			fread(&talmid, sizeof(std1), 1, fp);
		}
		fclose(fp);
	}
	avg=avg/count;
	return avg;
}
void SortFile(char *s, char *nf)
{
	FILE *fp;
	FILE *fp2;
	FILE *fp3;
	std1 talmid;
	int min;
	if((fp3=fopen(nf, "wb"))!=NULL)
	{
		while(!feof(fp3))
		{
			fp=fopen(s, "rb");
			fread(&talmid, sizeof(std1), 1, fp);
			min=talmid.code;
			fp2=fp;
			if((fp=fopen(s, "rb"))!=NULL)
			{
				fread(&talmid, sizeof(std1), 1, fp);
				while(!feof(fp))
				{
					if(min>talmid.code)
					{
						min=talmid.code;
						fp2=fp;
					}
					fread(&talmid, sizeof(std1), 1, fp);
				}
				talmid.code=-1;
				fwrite(&talmid, sizeof(std1), 1, fp2);
				fclose(fp);
			}
			talmid.code=min;
			fwrite(&talmid, sizeof(std1), 1, fp3);
		}

	fclose(fp3);
	}
}