Confusing error when writing structure to file in C - c

Question

i'm trying to write a structure to a dat file, everything works fine but the data in the dat file turns into random characters (it's the same in other formats like txt)
#include <stdio.h>
#include <string.h>
struct Product
{
char ProId[20];
char ProName[30];
float Price;
int Quantity;
int CatId;
};
int main(){
FILE *f;
f = fopen ("Product.dat", "w+");
if (f == NULL)
{
fprintf(stderr, "\nError opened file\n");
}
Product p1;
strcpy(p1.ProId, "1");
strcpy(p1.ProName, "Candy");
p1.Price = 4.5;
p1.Quantity = 5;
p1.CatId = 1;
fwrite(&p1, sizeof(p1), 1, f);
fclose(f);
return(0);
}
The data in Product.dat:
1 u ÿÿÿÿCandy Ù$# #
I tried searching for this error but to no avail. Please help me, what is wrong?
Thank you.

Answer 1

I compile and ran your code on my WSL2, and met the same problem, here is the hexdump:
00000000 31 00 00 00 00 00 00 00 e7 6a 5b 66 fd 7f 00 00 |1........j[f....|
00000010 e6 6a 5b 66 43 61 6e 64 79 00 d4 1a 18 56 00 00 |.j[fCandy....V..|
00000020 e8 32 96 dd 70 7f 00 00 80 12 d4 1a 18 56 00 00 |.2..p........V..|
00000030 00 00 00 00 00 00 90 40 05 00 00 00 01 00 00 00 |.......#........|
The string "Candy" is indeed copied to the struct.
I assume the reason it is polluted by some trash data is because this struct is allocated on stack.
So I made a clean up after the declaration of this struct, and here is the effect:
00000000 31 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |1...............|
00000010 00 00 00 00 43 61 6e 64 79 00 00 00 00 00 00 00 |....Candy.......|
00000020 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00000030 00 00 00 00 00 00 90 40 05 00 00 00 01 00 00 00 |.......#........|
Here is the code I modified, note the call to memset():
#include <stdio.h>
#include <string.h>
struct Product
{
char ProId[20];
char ProName[30];
float Price;
int Quantity;
int CatId;
};
int main(){
FILE *f;
f = fopen ("Product.dat", "w+");
if (f == NULL)
{
fprintf(stderr, "\nError opened file\n");
}
struct Product p1;
memset(&p1, 0, sizeof(p1));
strcpy(p1.ProId, "1");
strcpy(p1.ProName, "Candy");
p1.Price = 4.5;
p1.Quantity = 5;
p1.CatId = 1;
fwrite(&p1, sizeof(p1), 1, f);
fclose(f);
return(0);
}