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What is the difference between & and && in C?

Here, operator & is Bitwise AND and Address of Operator, while && is Logical AND Operator.

& as "Address of" Operator

Operator & is a Unary Address Of Operator which returns address of a variable. Basically & is used two times when we are storing values in variable and print the address of any variable.

Consider the following code snippet

scanf("%d",&num);
printf("Address of num: %8X\n",&num);

In the first statement integer value will be stored in num because &num pointing the address of variable num.

In the second statement address of num will print.

& as "Bitwise AND" Operator

Bitwise AND Operator (&) is Binary Operator because it operates on two operands and used for Bitwise AND operation.

Consider the following code snippet

int x=3;
if(x&1)
	printf("ONE");
if(x&2)
	printf("TWO");

In this statement value of x is 3, so both bits are 1, condition (x&1) and (x&2) will be true and "ONETWO" both messages will print.

Logical AND Operator (&&)

Logical AND (&&) is a Binary Operator which is used to check more than one conditions at a time and if all conditions are true result will be true.

Consider the following code snippet

int x=10;
int y=20;

if(x==10 && y==20)
	printf("TRUE");
else
	printf("FALSE");

In this statement both conditions x==10 and y==20 are true, hence "TRUE" will print.