5.2.4. Listing valid programs

Try these first

1. 1.

   What is a finite alphabet? Provide an example.

   Hint

   Think of a simple set of characters.

2. 2.

   Define Π* in your own words.

   Hint

   Link it with the concept of string formation.

3. 3.

   What does Π* represent?

   • Set of all programming languages
   • Set of all possible strings from an alphabet
   • Set of valid programs

   Hint

   Remember the definitions regarding finite sets.

4. 4.

   True or False: The set of valid programs is uncountable.

   • True
   • False

   Hint

   Reflect on the properties of subsets in mathematics.

5. 5.

   Given a finite alphabet {x, y}, list all possible strings of length 3 and state how many such strings exist.

   Hint

   Consider combinations of each character arranged in different orders.

6. 6.

   Create a valid program using a finite alphabet composed of basic arithmetic operations and variables. Explain why your program is valid.

   Hint

   Use starting and ending keywords with correct syntax.