C data types, arrays and structs

C-Data Types,
Arrays and Structs
PREPARED BY SAAD SHAIKH.

Data Types
 The basic definition of a data type is a data storage
format that can contain a specific type or range of
values.
 When computer programs store data in variables, each
variable must be assigned a specific data type.

Types of Data Types
 Primary Data Types
 They are arithmetic types and are further classified into:
(a) Integer types, (b) Character and (c) Floating-point types.
 Derived Data Types:
 They include (a) Pointer types, (b) Array types, (c) Structure types, (d) Union
types and (e) Function types.
 User Defined Data Types:
 They include TypeDef and ENUM.

Integer Type
 Integers are a commonly used data type in computer programming. An
integer is a whole number (not a fraction) that can be positive, negative, or
zero.
 It is denoted by “int” .
Type Storage Size Value Range
Int 2 or 4 bytes -32,768 to 32,767 or -
2,147,483,648 to
2,147,483,647
unsigned int 2 or 4 bytes 0 to 65,535 or 0 to
4,294,967,295
short 2 bytes -32,768 to 32,767
unsigned short 2 bytes 0 to 65,535
long 4 bytes -2,147,483,648 to
2,147,483,647
unsigned long 4 bytes 0 to 4,294,967,295

Floating Point Type
 As the name implies, floating point numbers are numbers that contain
floating decimal points. For example, the numbers 5.5, 0.001, and -
2,345.6789 are floating point numbers.
 Denoted by keyword “float”.
Type Storage size Value Range Precision
float 4 byte 1.2E-38 to
3.4E+38
6 decimal places
double 8 byte 2.3E-308 to
1.7E+308
15 decimal places
long double 10 byte 3.4E-4932 to
1.1E+4932
19 decimal places

Character Data Types
 Character data type allows a variable to store only one character.
 “char” keyword is used to refer character data type.
Type Storage size Value range
char 1 byte -128 to 127 or 0 to 255
unsigned char 1 byte 0 to 255
signed char 1 byte -128 to 127

Example Code:
#include <stdio.h>
void main()
{
int i = 20;
float f = 3.1415;
char c;
c = 'd';
printf("This is my float: %f n", f);
printf("This is my integer: %d n", i);
printf("This is my character: %c n", c);
}

VOID DATA TYPE
 The void type has no values therefore we cannot declare it as variable as we
did in case of integer and float.
 The void data type is usually used with function to specify its type.

User Defined Data Types
 User defined data types are those data types which are created by the
user to characterize the existing data types.
 This user defined data type can later be used to declare variables.
 In other words we are redefining the name of existing data types.

User Defined Data Types-Enum:
 An enumeration is a user-defined data type consists of integral constants and
each integral constant is give a name. Keyword enum is used to defined
enumerated data type.
 Syntax: enum type_name{ value1, value2,...,valueN };
 Here, type_name is the name of enumerated data type or tag. And value1,
value2,....,valueN are values of type type_name.
 By default, value1 will be equal to 0, value2 will be 1 and so on but, the
programmer can change the default value.

Example:
#include<stdio.h>
#include<conio.h>
Enum Weekday
{
Sun,Mon,Tues,Wed,Thus,Fri,Sat
};
Int main ()
{
enum Weedkday wd;
wd = Thus;
printf(“%d”,wd):
}
4
Output

User Defined Data Types-typedef
The C programming language provides a keyword called typedef, which you can
use to give a type, a new name.
 Syntax:
typedef <type><identifier>;
 Example:
typedef int score;
Score player1,player2;

Derived Data Types: ARRAY
 Array is a kind of data structure that can store a fixed-size sequential collection
of elements of the same type.
 An array is used to store a collection of data, but it is often more useful to think
of an array as a collection of variables of the same type.
 All arrays consist of contiguous memory locations.
First Element Last Element
a[1]a[0] a[2] a[3] a[4] a[5] a[6] a[7] a[n]

Declaring Arrays
 To declare an array in C, a programmer specifies the type of the elements
and the number of elements required by an array as follows :
type arrayName [ arraySize ];
 For example we can declare a 10 element array like:
int marks [10];

Initializing Array
 We can initialize an array in C either one by one or using a single
statement as follows:
double price[5] = {1000.0, 2.0, 3.4, 7.0, 50.0};
 The number of values between braces { } cannot be larger than the
number of elements that we declare for the array between square brackets
[ ].

Example:
#include <stdio.h>
int main ()
{
int n[ 10 ];
/* n is an array of 10 integers */
int i,j;
/* initialize elements of array n to 0 */
for ( i = 0; i < 10; i++ ) {
n[ i ] = i + 100;
/* set element at location i to i + 100 */
}
/* output each array element's value */
for (j = 0; j < 10; j++ ) {
printf("Element[%d] = %dn", j, n[j] );
}
return 0;
}
Element[0] = 100
Element[1] = 101
Element[2] = 102
Element[3] = 103
Element[4] = 104
Element[5] = 105
Element[6] = 106
Element[7] = 107
Element[8] = 108
Element[9] = 109
Output

Multidimensional Arrays
 Array having more than one subscript variable is called multidimensional array.
 Multidimensional array is also called as matrix
 To declare a two-dimensional integer array of size [x][y], you would write
something as follows:
type arrayName [ x ][ y ];
 To initialize multidimensional array we specify bracketed value of each row; for
example:
int a[3][4] = {
{0, 1, 2, 3} , /* initializers for row indexed by 0 */
{4, 5, 6, 7} , /* initializers for row indexed by 1 */
{8, 9, 10, 11} /* initializers for row indexed by 2 */
};

Example:
#include <stdio.h>
int main () {
/* an array with 5 rows and 2 columns*/
int a[5][2] = { {0,0}, {1,2}, {2,4}, {3,6},{4,8} };
int i, j;
/* output each array element's value */
for ( i = 0; i < 5; i++ )
{
for ( j = 0; j < 2; j++ ) {
printf("a[%d][%d] = %dn", i,j, a[i][j] );
}
}
return 0;
}
a[0][0]: 0
a[0][1]: 0
a[1][0]: 1
a[1][1]: 2
a[2][0]: 2
a[2][1]: 4
a[3][0]: 3
a[3][1]: 6
a[4][0]: 4
a[4][1]: 8
Output :

Structures
 Arrays allow to define type of variables that can hold several data items of the
same kind. Similarly structure is another user defined data type available in C
that allows to combine data items of different kinds.
 Structures are used to represent a record. Suppose you want to keep track of
your books in a library.
You might want to track the following attributes about each book like:
Title
Author
Subject
Book ID

Defining Structures
 To define a structure, you must use
the struct statement.
 The format is as follows:
struct [structure tag] {
member definition;
member definition;
...
member definition;
} [one or more structure variables];
Example:
struct Books {
char title[50];
char author[50];
char subject[100];
int book_id;
}
book;

Accessing Structure Members
 To access any member of a structure, we use the member access operator
(.).

Example:
#include <stdio.h>
#include <string.h>
struct Books
{
char title[50];
char author[50];
char subject[100];
int book_id;};
int main( )
{
struct Books Book; /* Declare Book of type Book */
/* book specification */
strcpy( Book.title, "C Programming");
strcpy( Book.author, "Aptech");
strcpy( Book.subject, "C Programming");
Book.book_id = 6495407;
/* print Book info */
printf( "Book title : %sn", Book.title);
printf( "Book author : %sn", Book.author);
printf( "Book subject : %sn", Book.subject);
printf( "Book book_id : %dn", Book.book_id);
return 0;
}
Book title : C Programming
Book author : Aptech
Book subject : C Programming
Book book_id : 6495407
Output :

C data types, arrays and structs

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