Chapter 16 Bits, characters, string, and structures

1. Structures are collections of related variables, sometimes referred to as 
   aggregates, under one name.

2. Structures can contain variables of different types.

3. The keyword struct begins every structure definition. Within the braces of 
   the structure definition are the structure member declaration.

4. Members of the same structure must have unique names.

5. A structure definition creates a new data type that can be used to decalre 
   variables.

6. A structure can initialized with an initializer list by following the variable 
   in the declaration with an equal sign and a comma-separated list of 
   initializers enclosed in braces. If there are fewer initializers in the list 
   than the members in the structure, the remaining members are automatically 
   initilized to zero (or NULL for pointer members).

7. Entire structure variables may be assigned to structure variables of the
   same type.

8. A structure variable may be initilized with a structure variable of the 
   same type.

9. Structure variables and individual structure members are passed to functions 
   call-by-value. Array members are, of course, passed-by-reference.

10. To pass a structure call-by-reference, pass the address of the structure 
    variable.

11. A array of structure is automatically passed-by-reference.

12. To pass an array call-by-value, create a structure with the array as a member.

13. Create a new name with typedef does not create a new type; it create a name 
    that is synonymous to a type defined previously.

14. The bitwise AND operator (&) takes two integral opeands. A bit in the result 
    is set to 1 if the corresponding bits in each of the operands are 1.

15. The bitwise OR operator (|) takes two integral opeands. A bit in the result 
    is set to 1 if either one of the corresponding bits in each of the operands 
    is 1.

16. The bitwise exclusive OR operator (^) takes two operands. A bit in the result 
    is set to 1 if exactly one of the corresponding bits in the two operands is 1.

17. The left shift operator (<<) shifts the bits of its left operand left by the 
    number of bits specified by its right operand. Bits vacated to the right are 
    replaced with 0s.

18. The right shift operator (>>) shifts the bits of its left operand right  by
    the number of bits specified by its right operand. Bits vacated to the left 
    are replaced with 0s if it is unsigned integer, otherwise it can be replaced 
    by sign bit or 0s depend on machine.

19. The bitwise complement operator (~) takes one operand and reverses its 
    bits -- this produces the one's complement of the operand.

20. Bit fields members must be declared as int or unsigned. A bit field is 
    declared by following an unsigned or int member name with a colon and the 
    width of the bit field.

21. An unsigned bit field with width 0 is used to align the next bit field on a 
    new machine word boundary.

22. The following convertion functions are useful:
 	islower	 isupper	isdigit	isalpha	isalnum	isxdigit	toupper	
        tolower	 isspace	iscntrl	ispunct	isgraph	ato	atoi	atol	
        strtod	strtol	strtoul	strchr  strcspn	strpbrk	strrchr	strspn	strstr	
        memcpy	memmove	memmp	memchr	memset	strerror



23. Provide a structure name when creating a structure type. The structure name 
    is convenient for declaring new variables of the sturcture type later in the 
    program and is required if the structure will be passed as a parameter to a 
    function.

24. Capitalize typedef name to emphasize that these names are synonyms for other 
    type names.

25. Although the bit fields save space, using them can ause the compiler to 
    generate slower executing machine language code. This occurs because it 
    takes extra machine instructions to access only portions of an addressable 
    storage unit. This is one of the many space-time tradeoffs that occur in 
    computer science.