Behaviour of sizeof operator in C

c, sizeof, struct

Solution

It is called Structure Padding

Having data structures that start on 4 byte word alignment (on CPUs with 4 byte buses and processors) is far more efficient when moving data around memory, and between RAM and the CPU.

You can generally switch this off with compiler options and/or pragmas, the specifics of doing so will depend on your specific compiler.

Hope this helps.

Problem

I am getting unusual behaviour with my code, which is as follows ``` #include<stdio.h> struct a { int x; char y; }; int main() { struct a str; str.x=2; str.y='s'; printf("%d %d %d",sizeof(int),sizeof(char),sizeof(str)); getch(); return 0; } ``` For this piece of code I am getting the output: ``` 4 1 8 ``` As of my knowledge the structure contains an integer variable of size 4 and a char variable of size 1 thus the size of structure a should be 5. But how come the size of structure is 8. I am using visual C++ compiler. Why this behaviour?

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