**Assigning values to variables**


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In Tcl, everything may be represented as a string, although internally it may be represented as a list, integer, double, or some other type, in order to make the language fast.

The assignment command in Tcl is `set`.

When `set` is called with two arguments, as in:
======tcl
    set fruit Cauliflower
======

it assigns the value `Cauliflower` (the second argument) to the variable `fruit` (the first argument). `set` always returns the contents of the variable named in the first argument.  Thus, when `set` is called with two arguments, it assigns the second argument to the variable named in the first argument and then returns the second argument.  In the above example, for instance, it would return `Cauliflower`.

The first argument to a `set` command can be either a single word, like `fruit` or `pi` , or it can be a member of an array, like `course(first)`, an element called `first` in the array `course`.  Technically speaking, arrays in Tcl are ''associative'' arrays. Arrays will be discussed in greater detail later.

`set` can also be invoked with only one argument.  When called with just one argument, it will return the contents of that argument.

Here's a summary of the `set` command.

   `set varName ?value?`:   If `value` is specified, then the contents of the variable `varName` are set equal to `value`.

   * If `varName` consists only of alphanumeric characters, and no parentheses, it is a scalar variable.
   * If `varName` has the form `varName(index)`, it is a member of an associative array.

If you look at the example code below, you'll notice that in the `set` command the first argument is typed with only its name, but in the `puts` statement the argument is preceded with a dollar sign (`$`).

The dollar sign tells Tcl to use the value of the variable -- in this case, `X` or `Y`.

Tcl passes data to subroutines either by name or by value. Commands that don't change the contents of a variable usually have their arguments passed by value.  Commands that '''do''' change the value of the data must have the data passed by name.


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***Example***

======tcl
set X "This is a string"

set Y 1.24

puts $X
puts $Y

puts "..............................."

set label "The value in Y is: "
puts "$label $Y"
======

<<discussion>> Resulting output
======none
This is a string
1.24
...............................
The value in Y is:  1.24
======

<<enddiscussion>>

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