a) In programming, a variable is defined as a location in the main memory where a value can be stored and changed during program execution. Briefly explain TWO (2) rules that need to be followed when giving a variable's name.

Problem Statement       The barcode used by the U.S. Postal System to route mail is defined as follows:  Each decimal digit in the ZIP code is encoded using a sequence of three half-height and two full-height bars.  The barcode starts and ends with a full-height bar (the guard rail) and includes a checksum digit (after the five-digit ZIP code or ZIP + 4), computed by summing up the original digits modulo 10.   Define the following functions:   Draw a half-height or full-height bar on stddraw. Given a digit, draw its sequence of bars. Compute the checksum digit.   Also define global code that read in a five- (or nine-) digit ZIP code as the command-line argument and draws the corresponding postal barcode.

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