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Consider the following JavaScript program:
var x, y, z;
function sub1() {
var a, y, z;
function sub2() {
var a, b, z;
. . .
}
. . .
}
function sub3() {
var a, x, w;
. . .
}
List all the variables, along with the program units where they are declared, that are visible in the bodies of sub1, sub2, and sub3, assuming static scoping is used.

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ibnahmadbello

Answer:

Variable       Where Declared

In Sub1 :

        A        Sub1

        Y        Sub1

        Z        Sub1

        X        Main

In Sub2:

        A        Sub2

        B        Sub2

        Z        Sub2

        Y        Sub1

        X        Main

In Sub3 :

        A        Sub3

        X        Sub3

        W       Sub3

        Y        Main

        Z        Main

Explanation:

In static-scoped languages with nested subprograms, the declaration of a variable is checked with the subprogram, if it is not found, it check within the parent method that called it, it continue until it find a declaration, if no declaration is found, it display an error.

In Sub1, a, y, z is declared there while the declaration of x is found in main.

In Sub2, a, b, z is declared, declaration of y is found in sub1 and declaration of x is found in main.

In Sub3, a, x, w is declared while the declaration of y, z is from the main.

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