22.14 Library Functions

Implementation-Defined Behavior for Library Functions is covered in section G.3.14 of the ANSI C Standard.

What is the null pointer constant to which the macro NULL expands? (ISO 7.1.5)

0.

How is the diagnostic printed by the assert function recognized, and what is the termination behavior of this function? (ISO 7.2)

The assert function prints the file name, line number and test expression, separated by the colon character (‘:’). It then calls the abort function.

What characters are tested for by the isalnum, isalpha, iscntrl, islower, isprint and isupper functions? (ISO 7.3.1)

Table 22-5. Characters Tested by is Functions
Function Characters tested
isalnum One of the letters or digits: isalpha or isdigit.
isalpha One of the letters: islower or isupper.
iscntrl One of the five standard motion control characters, backspace and alert: \f, \n, \r, \t, \v, \b, \a.
islower One of the letters ‘a’ through ‘z’.
isprint A graphic character or the space character: isalnum or ispunct or space.
isupper One of the letters ‘A’ through ‘Z’.
ispunct One of the characters: ! “ # % & ' ( ) ; < = > ? [ \ ] * + , - . / : ^

What values are returned by the mathematics functions after a domain errors? 
(ISO 7.5.1)

NaN.

Do the mathematics functions set the integer expression errno to the value of the macro ERANGE on underflow range errors? (ISO 7.5.1)

Yes.

Do you get a domain error or is zero returned when the fmod function has a second argument of zero? (ISO 7.5.6.4)

Domain error.