Identifiers are names created by the programmer to identify various objects in the program
syntax of identifiers:
Examples:
student_1 sum height
Unlimited length; Upper/lower case irrelevant
Cannot use reserved words; should not use pre-defined words.
identifiers should be as meaningful as possible, without being verbose
s1 the_first_student_on_the_course
student_1 first_student
i,j,N are ok to represent mathematical notions
avoid similar identifiers (helps avoid typos)
student_1 student_2