Must freads be in order? - c

Question

So I'm writing a code for a program with multiple menus that write different struct datas to a file and then with another menu that displays the data written in those files. Here's the code for the menu:
void displayall()
{
FILE *fp;
int choice=0;
struct depart loc = {0};
struct arrive loc1 = {0};
struct travel trav = {0};
fp=fopen("traveldat.dat","r");
while (1)
{
fread(&loc,sizeof(loc),1,fp);
fread(&loc1,sizeof(loc1),1,fp);
fread(&trav,sizeof(trav),1,fp);
double distance,time;
distance = sqrt(pow((loc1.x2-loc.x1),2)+pow((loc1.y2-loc.y1),2));
time = distance/trav.spd;
if (feof(fp))
{
break;
}
printf("\tYour departure location is : %s\n",loc.dep);
printf("\tWith the x-coordinate : %.2f\n",loc.x1);
printf("\tAnd the y-coordinate : %.2f\n\n",loc.y1);
printf("\tYour destination location is : %s\n",loc1.dest);
printf("\tWith the x-coordinate : %.2f\n",loc1.x2);
printf("\tAnd the y-coordinate : %.2f\n\n",loc1.y2);
printf("\tThe distance between these two locations is : %.2fkm\n\n",distance);
printf("\tYour preferred travel method is : %s\n",trav.mthd);
printf("\tWhich has a top speed of : %.2f km/h\n\n",trav.spd);
printf("\tYour expected travel time is : %.2f hours*\n\n",time);
printf("\t*Estimation,actual travel times may vary depending on certain conditions\n\n");
printf("\tThe system will now display the Main Menu\n\n");
}
fclose(fp);
}
The problem I'm facing is that if I go to the menu that writes loc1 or trav before the menu that writes loc, the display menu doesn't work, returns to the main menu, and then refuses to open whenver I try to access it. Is it because fread(&loc) is placed before the other freads? Or is there something I'm missing? Apologies in advance if this code is an eyesore or if I'm asking wrongly, I've only been learning programming for about a month.
Edit: loc1 and loc code as requested
void arrival_location_menu()
{
FILE *fp;
int choice=0;
struct arrive loc1;
fp=fopen("traveldat.dat","a");
printf("Please select your option (Destination location)\n");
printf("1.HOME\n");
printf("2.Andromeda Galaxy\n");
printf("3.The Library\n");
printf("4.Cprogramming.com\n");
printf("5.Return to main menu\n");
scanf("%d",&choice);
fflush (stdin);
switch (choice)
{
case 1: loc1.x2 = 3750;
loc1.y2 = 3450;
loc1.dest = "HOME";
system("CLS");
break;
case 2: loc1.x2 = 9870;
loc1.y2 = 5660;
loc1.dest = "Andromeda Galaxy";
system("CLS");
break;
case 3: loc1.x2 = 1367;
loc1.y2 = 3123;
loc1.dest = "The Library";
system("CLS");
break;
case 4: loc1.x2 = 2133;
loc1.y2 = 4767;
loc1.dest = "stackoverflow.com";
system("CLS");
break;
case 5: system("CLS");
break;
default: printf("Invalid option! Returning you to main menu...\n");
}
fwrite(&loc1,sizeof(loc1),1,fp);
fclose(fp);
return;
}
//DEPARTURE MENU
void departure_location_menu()
{
FILE *fp;
int choice=0;
struct depart loc;
fp=fopen("traveldat.dat","w");
printf("Please select your option (Departure location)\n");
printf("1.UTAR\n");
printf("2.PLUTO\n");
printf("3.IDK\n");
printf("4.UMM\n");
printf("5.Return to main menu\n");
scanf("%d",&choice);
fflush (stdin);
switch (choice)
{
case 1: loc.x1 = 1738;
loc.y1 = 1997;
loc.dep = "UTAR";
system("CLS");
break;
case 2: loc.x1 = 9850;
loc.y1 = 5675;
loc.dep = "PLUTO";
system("CLS");
break;
case 3: loc.x1 = 1363;
loc.y1 = 3125;
loc.dep = "IDK";
system("CLS");
break;
case 4: loc.x1 = 2130;
loc.y1 = 4785;
loc.dep = "UMM";
system("CLS");
break;
case 5:
system("CLS");
break;
default: printf("Invalied option!\n");
}
fwrite(&loc,sizeof(loc),1,fp);
fclose(fp);
return;
}

Answer 1

You seem to be asking if you can read data from anywhere in the file. Yes you can.
There is a function called fseek() to adjust the file pointer. The file pointer is the location next read from or written too.
There is also a function called ftell() to read the current file pointer. That's important if you're going to change the file pointer and want to restore it later.
I would also suggest you get into the habit of initializing variables ( even if it's to NULL or zero ), and of checking return values from functions. These two simple things can make debugging so much simpler.
I believe user #m-m has already explained the coding logic error.