An address book manager written in C as a homework

AddressBook.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <conio.h>
#define MAX 100

struct PERSON {
	char fName[20]; /* emri i nje personi ne librin e adresave */
	char lName[20]; /* mbiemri i nje personi ne librin e adresave */
	char id[20]; /* ID i nje personi ne librin e adresave */
	char cel[20]; /* numri i telefonit te nje personi ne librin e adresave */
	char eMail[30]; /* e-mail i nje personi ne librin e adresave */
} pList[MAX]; /* lista e gjithe personave ne DB */

void shkruaj(char *filename, struct PERSON *p,int n);
void lexo(char *filename,struct PERSON *p,int n);
void printo(struct PERSON p);
int dblen(char *filename);
int kerkoSipas(int type,char* data);
void sort(char* filename,int type);
int fshi(char *filename,char* ID);
void modifiko(char *filename,char *id);
void consolePauser();

int main() {
	int zgjedhja,lng;
	
	while (1) {
		system("cls");
		printf("\t\tAddressBook\n\n\n");
		printf("1. Afisho te dhenat\n");
		printf("2. Shto person\n");
		printf("3. Fshi person sipas ID\n");
		printf("4. Modifiko person sipas ID\n");
		printf("5. Kerko sipas\n");
		printf("6. Rendit sipas\n\n");
		
		scanf("%d",&zgjedhja);
		
		switch(zgjedhja) {
			case 1:
				lng = dblen("db.lsd");
				lexo("db.lsd",pList,lng);
				for (int i=0;i<lng;i++)
					printo(pList[i]);
				
				consolePauser();
				break;
			
			case 2: ;
				struct PERSON human;
				
				printf("Emri: ");
				scanf("%s",human.fName);
				printf("Mbiemri: ");
				scanf("%s",human.lName);
				printf("ID: ");
				scanf("%s",human.id);
				printf("Telefon: ");
				scanf("%s",human.cel);
				printf("E-Mail: ");
				scanf("%s",human.eMail);
				
				//append into pList
				lng = dblen("db.lsd");
				lexo("db.lsd",pList,lng);
				pList[lng] = human;
				
				//write to db.lsd
				shkruaj("db.lsd",pList,lng+1);
				
				consolePauser();
				break;
			
			case 3: ;
				char id_qe_fshihet[20];
				int success;
				printf("Fshi person\n");
				printf("Jepni ID e personit qe do fshihet: ");
				scanf("%s",id_qe_fshihet);
				success = fshi("db.lsd",id_qe_fshihet);
				
				if (!success) {
					printf("ID nuk u gjet\n");
				}
				
				consolePauser();
				break;
			
			case 4: ;
				char id_modifiko[20];
				printf("Modifiko te dhenat per nje person\n");
				printf("ID qe do modifikohet: ");
				scanf("%s",id_modifiko);
				modifiko("db.lsd",id_modifiko);
				
				consolePauser();
				break;
			
			case 5: ;
				int kerko,fl;
				char cfare[20];
				printf("Kerko sipas:\n");
				printf("1. Emrit\n");
				printf("2. Mbimrit\n");
				printf("3. ID\n");
				printf("4. Telefonit\n");
				printf("5. E-Mailit\n");
				
				scanf("%d",&kerko);
				printf("Ke te kerkoje: ");
				scanf("%s",cfare);
				
				fl = kerkoSipas(kerko,cfare);
				if (fl == 0) {
					printf("Asnje rezultat\n");
				}
				consolePauser();
				break;
				
			case 6: ;
				int rendit;
				printf("Rendit sipas:\n");
				printf("1. Emrit\n");
				printf("2. Mbimrit\n");
				printf("3. ID\n");
				printf("4. Telefonit\n");
				printf("5. E-Mailit\n");
				
				scanf("%d",&rendit);
				sort("db.lsd",rendit);
				
				consolePauser();
				break;
				
			default:
				fprintf(stderr,"Komande e panjohur!");
				
				consolePauser();
			}
		}
	
	return 0;
}


void shkruaj(char *filename, struct PERSON *p,int n) {
	FILE *fp;
	fp = fopen(filename,"w+b");
	fwrite(p,sizeof(struct PERSON),n,fp);
	fclose(fp);
}

void lexo(char *filename,struct PERSON *p,int n) {
	FILE *fp;
	fp = fopen(filename,"r");
	fread(p,sizeof(struct PERSON),n,fp);
	fclose(fp);
}

void printo(struct PERSON p) {
	printf("Emri: %s\n",p.fName);
	printf("Mbiemri: %s\n",p.lName);
	printf("ID: %s\n",p.id);
	printf("Telefon: %s\n",p.cel);
	printf("E-Mail: %s\n\n",p.eMail);
	
}

int dblen(char *filename) {
	FILE *fp;
	int len=-1;
	struct PERSON tmp;
	fp = fopen(filename,"r");
	while ( !feof(fp) ) {
		fread(&tmp,sizeof(struct PERSON),1,fp);
		len++;
	}
	
	return len;
}


int kerkoSipas(int type,char* data) {
	int i;
	int flag=0;
	int lng = dblen("db.lsd");
	lexo("db.lsd",pList,lng);
	switch(type) {
		case 1: /* kerko sipas emrit */
			for (i=0;i<lng;i++){
				if (!strcmp(pList[i].fName,data)) {
					printo(pList[i]);
					flag++;
				}
					
			}
			
			break;
		
		case 2: /* kerko sipas mbiemrit */
			for (i=0;i<lng;i++){
				if (!strcmp(pList[i].lName,data)) {
					printo(pList[i]);
					flag++;
				}
					
			}
			
			break;
			
		case 3: /* kerko sipas ID */
			for (i=0;i<lng;i++){
				if (!strcmp(pList[i].id,data)) {
					printo(pList[i]);
					flag++;
				}
					
			}
			
			break;
			
		case 4: /* kerko sipas telefonit */
			for (i=0;i<lng;i++){
				if (!strcmp(pList[i].cel,data)) {
					printo(pList[i]);
					flag++;
				}
					
			}
			
			break;
			
		case 5: /* kerko sipas e-Mailit */
			for (i=0;i<lng;i++){
				if (!strcmp(pList[i].eMail,data)) {
					printo(pList[i]);
					flag++;
				}
					
			}
			
			break;
		
		default:
			printf("Zgjedhje e gabuar\n");
			return -1;
	}
	
	return flag;
}

void sort(char* filename,int type) {
	int length = dblen(filename);
	lexo(filename,pList,length);
	
	switch(type) {
		case 1: /* rendit sipas emrit */
			for (int i=0;i<length;i++) { 
				for (int j=i;j<length;j++) {
					if (strcmp( pList[i].fName, pList[j].fName ) == 1 ) {
						struct PERSON tmp = pList[j];
						pList[j] = pList[i];
						pList[i] = tmp;
					}
				}
			}
			
			break;
			
		case 2: /* rendit sipas mbiemrit */
			for (int i=0;i<length;i++) { 
				for (int j=i;j<length;j++) {
					if (strcmp( pList[i].lName, pList[j].lName ) == 1 ) {
						struct PERSON tmp = pList[j];
						pList[j] = pList[i];
						pList[i] = tmp;
					}
				}
			}
			
			break;
			
		case 3: /* rendit sipas ID */
			for (int i=0;i<length;i++) { 
				for (int j=i;j<length;j++) {
					if (strcmp( pList[i].id, pList[j].id ) == 1 ) {
						struct PERSON tmp = pList[j];
						pList[j] = pList[i];
						pList[i] = tmp;
					}
				}
			}
			
			break;
			
		case 4: /* rendit sipas telefonit */
			for (int i=0;i<length;i++) { 
				for (int j=i;j<length;j++) {
					if (strcmp( pList[i].cel, pList[j].cel ) == 1 ) {
						struct PERSON tmp = pList[j];
						pList[j] = pList[i];
						pList[i] = tmp;
					}
				}
			}
			
			break;
			
		case 5: /* rendit sipas emrit */
			for (int i=0;i<length;i++) { 
				for (int j=i;j<length;j++) {
					if (strcmp( pList[i].eMail, pList[j].eMail ) == 1 ) {
						struct PERSON tmp = pList[j];
						pList[j] = pList[i];
						pList[i] = tmp;
					}
				}
			}
			
			break;
			
		default:
			printf("Zgjedhje e gabuar");
			return;
	}
	
	/* printojme te dhenat */
	for (int i=0;i<length;i++)
		printo(pList[i]);
}


int fshi(char *filename,char* ID) {
	int length = dblen(filename);
	lexo(filename,pList,length);
	int index = -1;
	
	/* gjejme indeksin me id = ID */
	for (int i=0;i<length;i++) {
		if (!strcmp(pList[i].id,ID)) {
			index = i;
			break;
		}
	}
	
	if (index == -1) {
		return 0;
	}
	
	for(int i=index;i<length-1;i++) {
		pList[i] = pList[i+1];
	}
	
	shkruaj(filename,pList,length-1);
	return 1;
}


void modifiko(char *filename,char *id) {
	int length = dblen(filename);
	int index = -1;
	int mod;
	int again;
	char nuovo[20];
	
	lexo(filename,pList,length);
	
	/* gjejme indeksin me id = ID */
	for (int i=0;i<length;i++) {
		if (!strcmp(pList[i].id,id)) {
			index = i;
			break;
		}
	}
	
	if (index == -1) {
		printf("ID nuk u gjet");
		return;
	}
	printo(pList[index]);
	
	do {
		printf("Modifiko: \n");
		printf("1. Emrin\n");
		printf("2. Mbiemrin\n");
		printf("3. ID\n");
		printf("4. Telefonin\n");
		printf("5. Emailin\n");
		scanf("%d",&mod);
		
		switch(mod) {
			case 1:
				printf("Emri i ri: ");
				scanf("%s",nuovo);
				strcpy(pList[index].fName,nuovo);
				break;
				
			case 2:
				printf("Mbiemri i ri: ");
				scanf("%s",nuovo);
				strcpy(pList[index].lName,nuovo);
				break;
				
			case 3:
				printf("ID i ri: ");
				scanf("%s",nuovo);
				strcpy(pList[index].id,nuovo);
				break;
				
			case 4:
				printf("Telefoni i ri: ");
				scanf("%s",nuovo);
				strcpy(pList[index].cel,nuovo);
				break;
				
			case 5:
				printf("E-Mail i ri: ");
				scanf("%s",nuovo);
				strcpy(pList[index].eMail,nuovo);
				break;
			
			default:
				printf("Komande e gabuar!\n");
		}
		
		printf("Shtypni 0 nese doni te mos ndryshoni me, ");
		printf("ose cdo numer tjeter per te ruajtur te dhenat");
		scanf("%d",&again);
	} while (again);
	
	shkruaj(filename,pList,length);
}


void consolePauser() {
	printf("Shtypni nje buton per te vazhduar");
	getch();
	system("cls");	
}