How Do We Declare Structs and use in a C Program?

Using the following program...

#include <stdio.h>

struct student

{ char student_name [15];

int student_id, student_hours;

float studentgpa;

struct student * nextgpa;

int main()
{

struct student active = {"Homer Simpson",12345,150,3.27};
struct student alumni = {"Raul Gonzalez", 23456, 98, 1.34};
printf("Name: %13s %14s\n",active.student_name, alumni.student_name);
printf("ID: %13d %14d\n",active.student_id, alumni.student_id);
printf("gpa: %13.3f %14.3f\n",active.gpa, alumni.gpa);
printf("Hours: %13d %14d\n",active.total_hrs, alumni.total_hrs);
return 0;
}

By looking at each part of the program we can identify them.

 This is only the name of the struct, which can have anyone that you want.

{  

 Here, we are reserving 15 bytes of memory for each name, In other words, we are creating a string of the size of 30 characters. Therefore, there will be a space provided of 15 characters to include the name of the student.

Here we are reserving just 2 bytes of space for each variable because an integer uses 2 bytes. They're both numbers that is why they are integers.

Since gpa is a real number we are reserving 4 bytes of space to declare GPA, it's a real number (in other words it requires decimals).

Finally, if we want to know where the base address of  the struct is located we need a pointer. That's why we set up this pointer to know where the base address of the struct is, and from there we can find any element in the struct.

}                               

This  basically shows the logic behind building structs we have to know what kind of values we want and then we define our variables.

This is stored in RAM in the following way.

As all data type, the data type struct has a base address:

Assume that variable active (of data type struct student) has the base address 7690 (and requiring 27 contiguous bytes, to 7712).

Questions:

1. If we want to include a name in our struct, how do we tell C++ to do that ???

a) By sending a letter to the pope

b) char name[30], because we a re declaring a space available of 30 letters for each name or record.

c) by going to Christian's house and asking him

d) int 1000000

2.- If we want to know were our struct is located in RAM , it's possible by doing which of the following:

a) Singing the national anthem

b) by declaring a pointer for example mystruct * hereitis (mystruct the name of the struct, hereitis will hold the base adress of the struct)

c) by sending an e-mail to ricky martin

3.- if we have the following struct

yo{

char [8]

int hola, bye

float gpa}

How many bytes do I need per record

a) how am I supposed to know only God knows

b) Kirs and Charles ages squred + the number of people in the class

c) 16

d) none of the above

Answers:

1. b) char name[30], because we a re declaring a space available of 30 letters for each name or record.

2. b) by declaring a pointer for example mystruct * hereitis (mystruct the name of the struct, hereitis will hold the base adress of the struct)

3. c) 16

References:

http://www.dgp.toronto.edu/~ajr/209/notes/struct.html

http://www.ecs.soton.ac.uk/~dem/teaching/maths/proginc/chapter3/chapter3.htm

http://www.cdf.utoronto.ca/~tff/180/practicals/11structSort.html