sizeof(Header) giving wrong result

I have defined a struct like given but sizeof function gives one more than the actual size that is 13 why??
Can You plz help me.

Code:

---

typedef struct {
        char type[3];
        char code[3];
        unsigned short int width;
        unsigned short int height;
        char flags;
        char bgColorI;
        char pARatio;
}  HEADER;                                                  // size is 13

int main(int argc,char **argv)
{
        printf("%u", sizeof(HEADER));  // it gives 14 why?? thats is my question
}

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Because your system pads it so it's a multiple of 2 in this case.

However, if you use the packed attribute, it gives the correct size.

Code:

---

typedef struct {
        char type[3];
        char code[3];
        unsigned short int width;
        unsigned short int height;
        char flags;
        char bgColorI;
        char pARatio;
} __attribute__((packed)) HEADER;                                                  // size is 13

int main(int argc,char **argv)
{
        printf("%u", sizeof(HEADER));  // it gives 14 why?? thats is my question
}

---

Thanx it worked if You don mind can u help me a bit more

Code:

---

typedef struct {
        char type[3];
        char code[3];
        unsigned short int width;
        unsigned short int height;
        char flags;
        char bgColorI;
        char pARatio;
} __attribute__((packed)) HEADER;                                               

int main(int argc,char **argv)
{
        HEADER header;
        printf("%u", sizeof(HEADER));
 
        //here one block of HEADER type is accessed from a file viz. fread(&header,13,1,fptr);
 
        printf("%d",header.flags); //this gives -10 can you tell me the bitwise values of this 8 bits
}

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Quote:

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Originally Posted by kapil1089thekin

Thanx it worked if You don mind can u help me a bit more

Code:

---

typedef struct {
        char type[3];
        char code[3];
        unsigned short int width;
        unsigned short int height;
        char flags;
        char bgColorI;
        char pARatio;
} __attribute__((packed)) HEADER;                                               

int main(int argc,char **argv)
{
        HEADER header;
        printf("%u", sizeof(HEADER));
 
        //here one block of HEADER type is accessed from a file viz. fread(&header,13,1,fptr);
 
        printf("%d",header.flags); //this gives -10 can you tell me the bitwise values of this 8 bits
}

---

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1111 0110

Try googling for the two's complement.

Quote:

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Originally Posted by kapil1089thekin

I have defined a struct like given but sizeof function gives one more than the actual size that is 13 why??

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If you put a bunch of wooden beams together to create a house, do you expect the volume of the house to be equal to the volume of the wooden beams?