Final answer:
The value of the given expression forms a sentence that relates to the creator of a programming language, resulting in: 'Bjarne Stroustrup named his new programming language C++ because it is a successor to the C programming language.'
Step-by-step explanation:
The value of the given expression, which involves concatenating string variables in a specific order, can be determined by appending each string to the previous one, adhering to the sequence provided in the question. The strings are associated with the creator of a certain programming language, and this manipulation results in a sentence that describes this relation.
Thus, the value of the expression string1 + string5 + string3 + " " + string2 + string4 + string2 + " " + string3 + "." would be: Bjarne Stroustrup named his new programming language C++ because it is a successor to the C programming language.