Writing NULL char to file in C - c

Question

I am attempting to write an array of char to a BMP file in C. The problem with this is that whilst 0x00 values are required for the file, it seems C interprets this as the end of string when writing to the file i.e. as a NULL char. Is there any way I can override this and have C rely purely on what I say is the number of char I wish to pass?
Code for writing the header to file (this function is executed in main);
void writeFile(void){
unsigned char bmp1[54] = {
0x42, 0x4D, 0x36, 0x00,
0x0C, 0x00, 0x00, 0x00,
0x00, 0x00, 0x36, 0x00,
0x00, 0x00, 0x28, 0x00,
0x00, 0x00, 0x00, 0x02,
0x00, 0x00, 0x00, 0x02,
0x00, 0x00, 0x01, 0x00,
0x18, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00,
0x0C, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00,
0x00, 0x00
};
FILE *picFile = fopen("pic.bmp","w");
fprintf(picFile, bmp1, 54);
fclose(picFile);
}

Answer 1

Don't use fprintf() to write binary data, of course it's going to interpret its formatting string as a string. That's what it does!
Use fwrite(), and open your file in binary mode with "wb".
You can use sizeof to compute the size of the array, no need to hardcode the value:
FILE *picFile = fopen("pic.bmp", "wb");
if(picFile != NULL)
fwrite(bmp1, sizeof bmp1, 1, picFile);
fclose(picFile);
This works because it's in the same scope as the array declaration of bmp1.

Answer 2

The function fprintf() and its relatives are used to format some information and produce a string then write its characters1 into a file or put it on screen or store it into a given array of characters.
Use function fwrite() to write binary data; this function does not interpret the data you give it in any way and just writes the number of bytes you specify into the file.
Try this:
FILE *picFile = fopen("pic.bmp","w");
fwrite(bmp1, sizeof(bmp1), 1, picFile);
fclose(picFile);
(your call to fprintf() was erroneous, anyway)
1
The functions sprintf() and snprintf() (they put the generated string into a provided buffer of characters) copy the entire generated string onto their destination buffer, including the null terminating character.
The functions fprintf() (writes the string into a file) and printf() (puts the string on screen) do not put the null terminating character of the generated string into the output stream.
(Thanks #chux for pointing out that the C strings include the null terminating character.)