I can't display binary content - c

Question

I'm trying to write a simple phone book program. I have completed the first function and according to I observe it works without error. However, in second function (which is ""display()"") I can't show to user after I enter person knowledge. I'm working with binary mode. What the problem is in second function I couldn't understand. If you examine and help I'll be satisfied. Thanks in advance.
#include <stdio.h>
#include <stdlib.h> // "stdlib" library contains of exit() function
#include <malloc.h> // "malloc" library contains of malloc() function
#include <Windows.h> // "Windows" library contains of Sleep() function which waits the system as you want
#include <io.h> // "io" library contains of filelength() function
struct personKnowledge
{
char name[32];
char surname[32];
char number[32];
};
FILE *ptrFILE,*ptrFILE1;
long int recordLength,totalRecordLength,location;
static int counter = 0;
int number,totalRecordNumber;
void newRecord();
void display();
void deletE();
void add();
void update();
int main()
{
int choice;
do
{
printf("\n\t\t --- Phone Book Program ---");
printf("\n\n\t\t 1) New record"); // The options are being presented to user
printf("\n\n\t\t 2) Display person knowledge");
printf("\n\n\t\t 3) Delete someone");
printf("\n\n\t\t 5) Update person knowledge");
printf("\n\n\t\t 6) Exit");
printf("\n\n\nEnter your choice: ");
scanf("%d", &choice);
switch (choice)
{
case 1:
{
newRecord();
break;
}
case 2:
{
display();
break;
}
case 3:
{
break;
}
case 4:
{
break;
}
case 5:
{
break;
}
case 6:
{
printf("\nWorking has been completed.\n");
return 0;
}
default:
{
printf("\nWrong entry! The program has been terminated.\n");
break;
}
}
} while (choice >= 1 && choice <= 6);
return 0;
}
void newRecord()
{
if ((ptrFILE = fopen("Phone Book.dat", "wb")) == NULL)
{
printf("The file couldn't open\n");
exit(0);
}
system("cls"); // Screen is being cleaned
struct personKnowledge *p; // p means person
p = (struct personKnowledge *)malloc(sizeof(struct personKnowledge)); // Memory is being allocated
fflush(stdin);
recordLength = sizeof(p); // size of p
printf("|| For the %d. person ||\n", counter+1);
printf("\n\Express person name: "); // User is entering the person's knowledge and they are being saved in file
gets(p->name);
printf("Express %s's surname: ", p->name);
gets(p->surname);
printf("Express %s's number: ", p->name);
gets(p->number);
fwrite(&(*p), recordLength, 1, ptrFILE);
printf("\nPlease wait, information is saving to file..\n");
Sleep(750);
printf("*-* Saving operation has been completed succesfully. *-*\n");
free(p);
counter++;
fclose(ptrFILE);
}
void display()
{
if ((ptrFILE = fopen("Phone Book.dat", "rb")) == NULL)
{
printf("The file couldn't open\n");
exit(0);
}
system("cls"); // Screen is being cleaned
struct personKnowledge *s; // s means searching
s = (struct personKnowledge *)malloc(sizeof(struct personKnowledge));
fflush(stdin);
recordLength = sizeof(s);
totalRecordLength = filelength(fileno(ptrFILE));
totalRecordNumber = totalRecordLength / recordLength;
printf("\n\nExpress person record number which you search: ");
scanf("%d", &number);
location = (number - 1)*recordLength;
fseek(ptrFILE, location, SEEK_SET);
fread(&(*s), recordLength, 1, ptrFILE);
printf("\n*-* Person knowledge which you search *-*\n");
Sleep(750);
printf("Name: %s\n", s->name);
printf("Surname: %s\n", s->surname);
printf("Number: %s\n", s->number);
free(s);
fclose(ptrFILE);
}

Answer 1

recordLength = sizeof(p);
is wrong, this is the size of the pointer which is normally 4 on a 32 bit system and 8 on a 64 bit syste.
you need
recordLength = sizeof(*p);
or
sizeof(struct personKnowledge);
which gives you the size of the structure pointed by p.