Difference between variable assigning and literal constant?

Question

I am bit confused about assigning a value to variable and literal constants.

For example:

int age = 20;

age is a variable, and 20 is the value assigned to it.

And:

int AGE = 20; 

AGE is literal constant, 20 is the value assigned to it.

What is the difference? Will constants take the same two bytes in main memory as variables?

Answer 1

You are confused indeed:

 int age = 20;

assigns integer value 20 to a variable age .

int AGE = 20;

assigns integer value 20 to a variable AGE .

There's no difference.

Answer 2

 int AGE = 20; 

AGE is literal constant, 20 is the value assigned to it.

No, AGE is a variable, same as age (but with a different name).

To declare a constant:

const int AGE = 20;

To use a literal constant directly ( this is discouraged in modern C++ ):

#define AGE 20 // every time you use AGE, the literal "20" will be used instead

Answer 3

There is no difference in your case:

int age = 20;

is a variable named "age" with value 20.

int AGE = 20;

is a variable named "AGE" with value 20.

If you want to declare a constant with a specific type in your code using const prefix:

const int AGE = 20;

In other case, you can use the #define preprocessor:

#define AGE 20;

The difference between a variable and a constant (or literal constant) is that the constant, once defined, you cannot change its value.

Answer 4

AGE is literal constant, 20 is the value assigned to it.

Incorrect!

You cannot assign a value to a literal constant. The literal constant is the value assigned to the variable.

I got confused originally because my textbook and online resources give "int mynum = 20;" as an example of a literal constant and "int anum = 20;" as an example of a variable.

It wasn't until I read it over 100 times that I realized that both "mynum" and "anum" are variables whereas 20 is the literal constant.

Answer 5

Constant literals are like regular variables, occupy same size. The only difference is that the value of constant variable cannot be altered. We use the key word const to indicate a constant variable

const int AGE=20;

we capitalize the constant variable just to distinguish it from regular variables.

Answer 6

  int AGE = 20; 

AGE is literal constant, 20 is the value assigned to it.

AGE is just a variable name and 20 is a literal constant. More information http://www.cplusplus.com/doc/tutorial/constants/