2.1 Nameless structs

One way to use struct is to organize variable names. For example, I may have a name, an address and a phone number associated with a student. To store these pieces of information, I could do the following variable definitions:

char student_name[NAMESIZE];
char student_phone[PHNUMSIZE];
char student_address[ADDRSIZE];

But this gets tedious if I want to track information for two students concurrently. So, instead of defining individual variables, I can define a nameless struct:

struct
{
  char name[NAMESIZE];
  char phone[PHNUMSIZE];
  char address[ADDRSIZE];
} student;

Note that this is a variable definition, not a class definition! The name of the variable is student, and it so happens to have components called name, phone and address in it.

If I want to keep track of another student, I can change the definition as follows:

struct
{
  char name[NAMESIZE];
  char phone[PHNUMSIZE];
  char address[ADDRSIZE];
} studentA, studentB;

Now I have two variables of the same structure: studentA and studentB. If I want to compare the names of the students, I can do the following:

if (strncmp(studentA.name, studentB.name, NAMESIZE) < 0)
{
  // ...
}

The main drawback of this approach is that the struct is not named. As a result, I cannot refer to the structure of a student record explicitly. This also means that I cannot use it as to specify a parameter, or to create new student records elsewhere in the program.