How do we declare a struct in other languages

How do we declare a struct in other languages? How do we declare them in c?

Before entering into matter, we should begin by defining what a STRUCT is. A STRUCT is basically a new data type which can be manipulated in the same matter as any of the other basic data types (int, float, char, etc.) has the same properties as an array meaning that:

It has a fixed number or elements
Elements must be contiguous

WITH THE EXEPTION OF ONE OF THE PROPERTIES OF AN ARRAY

All elements must be of the SAME data type

As a matter of fact, a STRUCT could be made of two or more data types. One common example, and perhaps the easiest to understand and explain, are DATABASES.

NAME	SSN	DOB	ADDRESS	OCCUPATION	AGE
Alfred Molina	987654321	6/25/1985	259 La Colina	Student	18

In this example, the following data types were used.

FIELD	DATA TYPE
Name	char*
SSN	char*
DOB	char*
Adress	char*
Occupation	char*
Age	Int

The preceding information raises one question

How many and what data types may be used in a STRUCT

There is no best way to combine the data types, they can be combined to suit the needs of the programmer. As far as how many data types can be used the topic is still highly debatable, consider the following table as the range of possible combinations.

Data Item	Data Type (variable)	Example	Comments
Name	char name[???]; char lastname[??], firstname[??];	“Smith, Joe” “Smith” “Joe”	How long is a name? Should we break up name? How long should each be?
SSN	char ssn[11]; char ssn[9]; long ssn; unsigned long ssn;	“123-45-6789” “123456789” 123456789 123456789	If we include hyphens Without hyphens Max Val: 2,147,483,647 Max Val: 4,294,967,295
DOB	char DOB[6]	4/6/1982	This is highly subjective, it depends on the preferred date format.
Address	char street[???]; char apt[???], street[???]; char street1[???], street2[???];	“123 Main St.” “Apt. 5A” “123 Main St.” “Mesa Village” “123 Main St.”	How Many Characters? Should we have this? How Many Characters? Should there be two lines? How Many Characters?
Occupation	char occupation[???];	"Student"	How long is occupation?
Age	unsigned long	18	This one is pretty easy.

To declare a STRUCT in another language one must obey the language’s instructions. For instance:

COBOL

01 Customer Info

02 Name PIC X(40).

02 SSN PIC 9(9).

02 DOB PIC 9(6).

02 Address PIC X(35).

02 Occupation PIC X(30).

02 Age PIC 9(3).

For instance, in COBOL the X or 9 in after PIC identifies the code on the specific field. For instance, 9 is numeric and X is Alpha-Numeric

PASCAL

Type Customer Info = record

Name : array [1..40] char

SSN : interger;

DOB : integer;

Adress :array[1..35] of char;

Occupation : array [1..30];

Age : integer;

end;

In PASCAL, the procedure is similar to c. The type of data to be used is declared after the title of the field.

These are just a couple of examples; the code will vary in accordance with the programming scheme of the language used.

When using c, we basically use a compilation of previously used data types and generate a new and distinct data type. The steps to declare a STRUCT in c are as follows

1 Continuing with the database example, we begin by determining what fields we wish to have in our record.

2 We then proceed to determine the data type for each to be used for each of the fields.

3 We then determine the amount of bytes to be assigned to each of the fields.

FIELD

Name

SSN

DOB

Adress

Occupation

Age

Data Type

char

3

2

int

Bytes

4 We conclude bye declaring the RECORD in c with accordance with the information previously selected.

struct Customer Info

{ char Name [31];

char SSN [10];

char DOB [5];

char Address [41];

int age [2]; };

int main()

{ struct Custmer Info active =

{"Favre, Brett",12345,"CIS",3.27,67};

struct student alumni =

{"White, Reggie", 23456, "Pain", 1.34, 89};

printf("Name: %13s %14s\n",active.student_name,

alumni.student_name);

printf("ID: %13d %14d\n",active.student_id,

alumni.student_id);

printf("Major: %13s %14s\n",active.major,

alumni.major);

printf("gpa: %13.3f %14.3f\n",active.gpa,

alumni.gpa);

printf("Hours: %13d %14d\n",active.total_hrs,

alumni.total_hrs);

return 0;}

*Why is there an extra byte allocated for Name, SSN, DOB, Address, Occupation, and Age if they should consist of 30, 10, 5, 40, and 30 correspondingly.

The reason for this, is because we are storing these fields as the data type character array, which means that we need to contemplate one extra byte for the null character. If we do not do this, we would have to keep track of the length of each of the strings.

How many total Bytes are needed for a STRUCT

a) 128 non-contiguous bytes.

b) 128 contiguous bytes.

c) 64 contiguous bytes.

d) less than 64 bytes.

ANSWER: B

What is the primary difference between a STRUCT and an array

a) There is no difference they are the same.

b) A Struct can only have one data type.

c) A Struct can have several data types.

d) A array can have does not need contiguous space.

ANSWER: C

OTHER GOOD REFERENCES

How stuff works

Ohio State University

Intro to STRUCT