C/stdio.h/fwrite

    
//Header file:     #include <stdio.h>  
//Declaration:     size_t fwrite(const void *buf, size_t size, size_t count, FILE *stream); 
//Return:          returns the number of items written on success. Fewer items written means failure. 
  
  #include <stdio.h>
  #include <stdlib.h>
  int main(void)
  {
    FILE *fp;
    float f=12.23;
    if((fp=fopen("test", "wb"))==NULL) {
      printf("Cannot open file.\n");
      exit(1);
    }
    fwrite(&f, sizeof(float), 1, fp);
    fclose(fp);
    return 0;
  }