Concept Of

Data Types

Lecture-06

REHAN IJAZ

By

Programm

ing Fundamentals

Data Type (causes & reasons)

A Data Type is a Type of Data.

Data types are the keywords, which are used for assigning a type to a

variable.

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.

In C, variable(data) should be declared before it can be used in program.

Whenever we declare variable in Computer’s memory, Computer must

know the type of the data to be stored inside the memory.

When the compiler encounters a declaration for a variable, it sets up a

memory location for it

If we need to store the single character then the size of memory occupied

will be different than storing the single integer number.

The memory in our computers is organized in bytes.

A byte is the minimum amount of memory that we can manage in C.

Data Type (causes & reasons)

Data TypesSyntax for declaration of a variable

data_type variable_name;

int var1;int std_reg_no;char std_gender;

Classifications of Data Types• Built-in data types

– Fundamental data types (int, char, double, float, void, pointer)– Derived data types (array, string, structure)

• Programmer-defined data types– Structure– Union– Enumeration

Data TypesData Type keyword Description

Integer Data Type int Stores the Integer Value

Float Data Type float Stores the Floating Point Value

Character Data Type char Stores the Single Character Value

Long Data Type long Stores the Long range Integer Value

Double Data Type double Stores the long range Floating Value

Range of Data TypesType 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

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

−To 

int - data typeint is used to define integer numbers.

float - data typefloat is used to define floating point numbers.

char - data typechar defines characters.

Purpose and syntax for Data Types

int rollno; rollno = 5;

float kilometre; kilometre = 5.6;

char section; section = ‘D';

double - data typedouble is used to define BIG floating point numbers. It reserves twice the storage for the number. On PCs this is likely to be 8 bytes.

Purpose and syntax for Data Types

double Atoms; Atoms = 2500000;

Purpose and syntax for Data Typespointer-data type

A pointer is a special kind of variable designed for storing memory address i.e. the address of another variable. Declaring a pointer is the same as declaring a normal variable except you stick an asterisk '*' in front of the variables identifier.

There are two new operators you will need to know to work with pointers. The "address of" operator '&' and the "dereferencing" operator '*'. When you place '&' in front of a variable you will get it's address, this can

be stored in a pointer vairable. When you place an '*' in front of a pointer you will get the value at the

memory address pointed to.

Purpose and syntax for Data Types

{int *ptr, q;/* address of q is assigned to ptr */ptr = &q;/* display q’s value using ptr variable */printf(“%d”, *ptr);

Output:

A0250

Example of pointer

Data Types

An array is a collection of values, all of the same type, stored contiguously

in memory.

An array of size N is indexed by integers from 0 up to and including N-1.

There are also "arrays of unspecified size" where the number of elements

is not known by the compiler. Here is a brief

1.One dimensional array 2. Two dimensional array

array

Data TypesArray (one dimensional)

#include<stdio.h> int main() { int arr[5] = {10,20,30,40,50}; printf(“value of arr[0] is %d \n”, arr[0]); }

Output : 10

Syntax : data-type arr_name[array_size];

//or arr[0] = 10; arr[1] = 20; arr[2] = 30; arr[3] = 40; arr[4] = 50;

0 1 2 3 4

4 5 3 1 9

Data TypesArray (two dimensional)

int arr[2][2] = {10,20,30,40};printf(“value of arr[%d] [%d] : \n”,arr[1][0]);

Output : 30

syntax : data_type array_name[num_of_rows][num_of_column]

// orarr[0][0] = 10;arr[0][1] = 20;arr[1][0] = 30;arr[1][1] = 40;

0 1

0 10 20

1 30 40

more about Data Types

To get the exact size of a type or a variable on a particular platform, you can use the sizeof operator. The expressions sizeof(type) yields the storage size of the object or type in bytes. Given below is an example to get the size of int type on any machine #include<stdio.h>

#include<limits.h> int main() {

printf("Storage size for int : %d \n", sizeof(int));

return 0; }

sizeof(type)

Type castingTypecasting concept in C language is used to modify a variable from one date type to another data type. New data type should be mentioned before the variable name or value in brackets which to be typecast.

#include <stdio.h> int main () { float x; x = (float) 7/5; printf("%f",x); }

Output: 1.400000

Type casting

S.no Typecast function Description

1 atof() Converts string to float

2 atoi() Converts string to int

3 atol() Converts string to long

4 itoa() Converts int to string

5 ltoa() Converts long to string

Thank you