Getting values from the Structure

[sajiv77]

See the program below and see the output.

#include <stdio.h>
#include <string.h>
#define SIZENUMBER 15

typedef unsigned char byte;

typedef struct
{
byte trans_no[SIZENUMBER];
byte s_no[2];
byte abc;
}XYZ;

main()
{
XYZ xy;
FILE *fp,*fp1;

memcpy(xy.trans_no,&quot;M02031315A0008&quot;,15);
xy.s_no[2] = 12;
xy.abc = 11;


printf(&quot;Number is %s \n&quot;,xy.trans_no);
printf(&quot;Number 2 is %d \n&quot;,xy.s_no[2]);
printf(&quot;Number 3 is %u \n&quot;,xy.abc);

fp = fopen(&quot;testfile&quot;,&quot;w&quot;
fwrite(&xy,sizeof(XYZ),1,fp);
fclose(fp);
fp1 = fopen(&quot;testfile&quot;,&quot;r&quot;
fread(&xy,sizeof(XYZ),1,fp1);
printf(&quot;Number from XYZ is %s \n&quot;,xy.trans_no);
printf(&quot;Number 2 XYZ is %d\n&quot;,xy.s_no[2]);
printf(&quot;Number 3 XYZ is %d\n&quot;,xy.abc);

fclose(fp1);
}


I am getting the output as
Number is M02031315A0008
Number 2 is 1
Number 3 is 1
Number from XYZ is M02031315A0008
Number 2 XYZ is 1
Number 3 XYZ is 1
though i should get the values of s_no as
12.
Is there anything wrong in the way i am filling these structures.I need to have all these varieties of elements in my program.

Thanks

 

[Jeffray]

You defined s_no as a two-byte char array. that is , s_no[0] and s_no[1]. s_no[2] is out of the index range and has exactly the same address as that of abc. That you set a value to abc, also means you set a value to s_no[2].