Tyl Programming Language
▶ VARIABLE ASSIGNMENT
Declare the `num_a` variable:
``` num_a ```
Assign the value: 21 to `num_a`:
``` num_a 21 ```
Consider this piece of code:
``` num_a print num_a num_a 21 print num_a num_a print num_a ```
NULL
21
NULL
After the first `num_a` declaration, `num_a` has no value, therefore its value is: NULL. In programming languages, the word: 'null' denotes: 'No Value'.
After the assignment line, the value of `num_a` is: 21.
The second line: `num_a`, will behave according to its position in the code block. If it is not the last statement it will cause the value of `num_a` to be: NULL. If it is the last statement it will return `num_a` value.

Declaration and assignment can be done in one line.
Declare and assign `num_b`:
``` num_b 22 ```
Variables can be assigned the value of another variable:
``` print 'Declare and assign num_a and num_b variables' num_a 21 num_b 22 print num_a print num_b print 'Assign the value of num_a to num_b' num_b num_a print num_a print num_b ```
Declare and assign num_a and num_b variables
21
22
Assign the value of num_a to num_b
21
21
In line: '`num_b num_a`', the value of `num_a` is copied (or assigned) to `num_b`. Note that though the variables have the same value, they are independent variables. Let's define the assignment by using the arrow symbol: '`→`'.
Then the assignment: '`num_b num_a`', will be denoted:
`num_a → num_b`

PART 2