Question

The following are invalid identifiers in C++. Write a reason for each.

a) Id#

b) void

c) 2ab

d) avg hgt​

Answer 1

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• Id# – Invalid because identifier name cannot contain any special characters (except dollars and underscores)

• void – Invalid because identifier name cannot be a keyword.

• 2ab – Invalid because identifier name cannot start with a digit.

• abc hgt – Invalid because identifier name cannot contain spaces.

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Naming rules for identifier.

• Identifier name must not be a keyword.
• It may contain alphabets, dollars and underscores only. No special characters are allowed.
• Identifier name must not contain any spaces.
• Identifier name must not start with a digit.

Answer 2

a) Id# - # (special character) cannot be used

b) void - void is a keywords, which cannot be used

c) 2ab -2 / digit cannot be used as the first character

d) avg hgt - space cannot be used