17. Understanding Structure Padding and Alignment

pravjot

Question: Consider the following structure definition in C:

struct Data

{

char a; // 1 byte

int b; // 4 bytes

short c; // 2 bytes

char d; // 1 byte

};

a) Calculate the size of this structure on a 32-bit system. Explain how the size is determined by considering alignment and padding.

b) If the order of the members is changed to the following:

struct Data
{

int b;
short c;
char a;
char d;

};

How does the size change, and why? Explain the impact of reordering members on structure padding.

mdaliakbar

We can avoid the structure padding in C in two ways:

1) Using #pragma pack(1) directive
2)Using attribute
I know pragma pack directory this is pre processor directive . But what is attribute and how can solve this problem. explain and 1 simple eg?

17. Understanding Structure Padding and Alignment

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