All the members of the structure can be accessed at
once,where as in an union only one member can be used at a time.
Another important difference is in the size allocated to a
structure and an union.
for eg:
struct example
{
int integer;
float floating_numbers;
}
the size allocated here is sizeof(int)+sizeof(float);
where as in an union
union example
{
int integer;
float floating_numbers;
}
size allocated is the size of the highest member.
so size is=sizeof(float);
1) Structure: The size in bytes is the sum total of size of
all the elements in the structure, plus padding bytes.
2) Size of in bytes of the union is size of the largest
variable element in the union.
i.e In case of Union, the elements making up the
union 'overlap' in memory OR they are accessed as diffrent
name/type at diffrent places in the program.
Whereas in case of Struct, each of the elements have a
distinct identity.
The difference between structure and union in c are: 1.
union allocates the memory equal to the maximum memory
required by the member of the union but structure allocates
the memory equal to the total memory required by the
members. 2. In union, one block is used by all the member
of the union but in case of structure, each member have
their own memory space
. union allocates the memory equal to the maximum memory
required by the member of the union but structure allocates
the memory equal to the total memory required by the
members.
2. In union, one block is used by all the member of the
union but in case of structure, each member have their own
memory space
1. Lets say a structure containing an int, char and
float is created and a union containing int char float are
declared. struct TT{ int a; float b; char c; } Union UU{
int a; float b; char c; }
2. sizeof TT(struct) would be >9 bytes (compiler
dependent-if int,float, char are taken as 4,4,1)
3. sizeof UU(Union) would be 4 bytes as supposed from
above.If a variable in double exists in union then the size
of union and struct would be 8 bytes and cumulative size of
all variables in struct
union u
{
union u
{
int i;
int j;
}a[10];
int b[10];
}u;
main()
{
printf("\n%d", sizeof(u));
printf(" %d", sizeof(u.a));
// printf("%d", sizeof(u.a[4].i));
}
a. 4, 4, 4
b. 40, 4, 4
c. 1, 100, 1
d. 40 400 4
void func1(int (*a)[10])
{
printf("Ok it works");
}
void func2(int a[][10])
{
printf("Will this work?");
}
main()
{
int a[10][10];
func1(a);
func2(a);
}
a. Ok it works
b. Will this work?
c. Ok it worksWill this work?
d. None of the above
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