# C++ > Algorithms Code Examples

## Byte alignment in a struct

``` Byte alignment in a struct #include <iostream.h> #define ALIGN 8 #pragma pack(ALIGN) /* Algorithm Byte offset between currentType and nextType = MIN( multiple of Byte Alignment specified , multiple of size of nextType) **/ int ALIGNOFFSET(int currRelativeAddess,int currrentTypeSize,int nextTypeSize) { int nOffset = currrentTypeSize ;//this is size of the current type.Offset will be minimum of this size. currRelativeAddess += currrentTypeSize ; //cuurent address is increased by size of current type. if( nextTypeSize < ALIGN) // now alignment depens on the next type and also alignment defined by #pragam pack(#) { // if the size of next type is less than byte alignment size specified , then offset will be increased to the muliple of // size of next type. int nRemainder = currRelativeAddess % nextTypeSize ; if(nRemainder != 0) { nOffset += nextTypeSize - nRemainder ;//this will align boundary to next multiple of nextTypeSize } } else { // if the byte alignment size specified is less than size of next type , then offset will be increased to the next muliple of // size of byte alignment. int nRemainder = currRelativeAddess % ALIGN ; if(nRemainder != 0) { nOffset += ALIGN - nRemainder ;//this will align the boundary to next multiple of ALIGN } } return nOffset ; } struct S { char a[2]; int b; double c; char d[1]; int e; double f; }; void main() { S sz; cout << "size of struct :" << sizeof(sz) << endl; cout << "address of size::a "<< &sz.a <<" Actual offset = " << int(0) << " Calculated offset = " << 0 << endl; int offset = ((int)&sz.b)- (int)(&sz.a); cout << "address of size::b " << &sz.b <<" Actual offset = " << offset << " Calculated offset = " << ALIGNOFFSET((int)(&sz.a)- (int)(&sz),sizeof(sz.a),sizeof(sz.b)) << endl; offset = ((int)&sz.c)- (int)(&sz.b); cout << "address of size::c " << &sz.c <<" Actual offset = " << offset << " Calculated offset = " << ALIGNOFFSET((int)(&sz.b) - (int)(&sz),sizeof(sz.b),sizeof(sz.c)) << endl; offset = ((int)&sz.d)- (int)(&sz.c); cout << "address of size::d " << &sz.d <<" Actual offset = " << offset << " Calculated offset = " << ALIGNOFFSET((int)(&sz.c)- (int)(&sz),sizeof(sz.c),sizeof(sz.d)) << endl; offset = ((int)&sz.e)- (int)(&sz.d); cout << "address of size::e " << &sz.e <<" Actual offset = " << offset << " Calculated offset = " << ALIGNOFFSET((int)(&sz.d)- (int)(&sz),sizeof(sz.d),sizeof(sz.e)) << endl; offset = ((int)&sz.f)- (int)(&sz.e); cout << "address of size::f " << &sz.f <<" Actual offset = " << offset << " Calculated offset = " << ALIGNOFFSET((int)(&sz.e)- (int)(&sz),sizeof(sz.e),sizeof(sz.f)) << endl; } ```