Data type

1
Fundamental Data Types
http://improvec.blogspot.in

2
Declaration
• All variables must be declared before
being used.
– Tells compiler to set aside an appropriate
amount of space in memory to hold a value.
– Enables the compiler to perform operations
using the declared variables.

3
Basic Data Types
• char character
• int integer
• float floating-point
• double double floating-point
• void valueless

4
Modifying the Basic Types
• Type modifier:
signed unsigned long short
• When a type modifier is used by itself, then int is
assumed.
Modifier Same As
signed signed int
unsigned unsigned int
long long int
short short int

5
Data Type char
Have Seen:Chars are treated as small integers &
conversely small ints are treated as chars.
char c = ‘a’;
printf (“%c”, c + 1) b
printf (“%d”, c + 2) 99
Each char variable stored in 1 Byte 8 Bits:
27
26
25
24
23
22
21
20
128 64 32 16 8 4 2 1
a
0000110 1http://improvec.blogspot.in

6
• String of binary digits are called bit
strings.
• A bit string is interpreted as a binary
number. bnbn-1
……
b2b1b0
0 1 1 0 0 0 0 1 a
• This bit string has the value:
1×26
+ 1×25
+ 1×20
= 97http://improvec.blogspot.in

7
3 types:
1) char 2) unsigned char 3) signed char
Each uses 1 Byte.
Signed char -128 to 127
Unsigned char 0 to 255

8
INTEGERS : Include the natural counting
numbers and their negatives.
INTEGRAL DATA TYPES:
int short long unsigned
Data Type int

9
• The magnitude of the number that an int
variable can hold depends on
___________?
2 Byte word ~ -32 K To +32K
-215
, …, -3, -2, -1, 0, 1, 2, 3, …, 215
-1
4 Byte word ~ -2 Billion To +2 Billion
-231
, …. -3, -2, -1, 0, 1, 2, 3, …, 231
-1
word size(bits) of the machine is machine dependent

10
• Integer overflow:
– Value too large for defined Storage Location.
– Typically program continues to run but
incorrect results.
– The programmer must strive at all times to
avoid integer overflow.

11
Types short, long, unsigned
• short - used where conserving storage is a
concern (usually 2 Bytes).
-32 Thousand To +32 Thousand
-215
, -215
+1, …, -3, -2, -1, 0, 1, 2, 3, …, 215
-1
• long - needed for larger integers (usually 4
bytes).
-2 Billion To +2 Billion
31 31 31

12
• Unsigned - no sign bit, same number
bytes as int.
The range, u, of values:
0 ≤ u ≤ 2wordsize
-1
2 Byte word ~ 0 To + 64 Thousand
0, 1, 2, 3, …, 216
-1
4 Byte word ~ 0 To + 4 Billion
0, 1, 2, 3, …, 232
-1http://improvec.blogspot.in

13
Suffix:
u - 20u
l – 20l
ul - 20ul
(case not significant)
IF no suffix with constant - system will choose the
first of : int - long - unsigned long
That can hold the value.

14
float double long double
• Suffixes for constants
f or F float 3.7 F
l or L long double 3.7 L
• Any unsuffixed floating constant is of type
double (working type).
The Floating Types

15
• Notation: exponential or decimal
Must have Exponent or Dec pt or Both.
1.234567e5 123456.7
1.234567e-3 0.001234567
0e0 correct 0.0
.e0 wrong
May not contain any blanks or special characters.
• Typical Storage: Float < Double

16
Precision: The number of significant decimal
digits that floating value carries.
Range: Limits of largest & smallest possible
values that can be in a variable of that
type.
Float: 4 Bytes - about 6 decimal places of
accuracy- single precision.
Double: 8 Bytes - about 15 decimal places
of accuracy- double precision.http://improvec.blogspot.in

17
Internal Representation
FLOAT:
01 8 9 31
SEEEEEEEE mmmmm…m
DOUBLE:
01 11 12 63
SEEEEEEEEEEE mmmmmmm…m
Implied mantissa of 1 is not stored.
Sign bit (1 for neg-otherwise pos).http://improvec.blogspot.in

18
Float:
Precision: 6 significant digits.
Range: 10-38
to 10+38
0.d1d2d3d4d5d6× 10n
Double:
Precision: 15 significant digits (252
≈ 1015
)
Range: 10-308
to 10+308
0.123451234512345 × 103

19
Note:
1. Not all Real numbers are exactly
representable in binary memory.
2. Floating Arithmetic ops, unlike integer
arithmetic, may not be exact.

20
• Unary operator used to find the number of Bytes
needed to store an object.
sizeof(object)
• Object
– Data type int , float, …
– Expression a + b
Array
Will cover
later
Structure
Compile-Time Operator sizeof

21
Assuming that integers are 4 bytes and
doubles are 8 bytes.
double f;
printf("%d ",sizeof (f)); 8
printf(''%d", sizeof(int)); 4

22
sizeof(char) = 1
sizeof(short) ≤ sizeof(int) ≤ sizeof(long)
sizeof(signed)=sizeof(unsigned)=sizeof(int)
sizeof(float)
<= sizeof(double )
<= sizeof( long double)

23
Conversions
• When constants and variables of different types
are mixed in an expression, the compiler converts
all operands to the type of the largest operand-
Called Type Promotion.
- First, all char and short values are automatically
elevated to int. Called integral promotion.
- int + int = int
- short + short = int
- Arithmetic Conversion (See pg. 217)

24
char ch;
int i;
float f;
double d,result;
result= (ch / i) + (f * d) – (f + i);
int double float
double

25
• Casts - Explicit conversions.
(type) expression
If i is int:
(float) i will change expression value to
float, i is not changed.
Casts
(float) i/2

26
• Apply to an Expression:
(float) (‘c’ + 3)
• Cannot apply to an Assignment:
(int) f = 3: illegal
• As an unary operator, a cast has the same
precedence as any other unary operator.
(float) i + 3 ( (float) i ) + 3

27
/* print i and i/2 with fractions */
int main(void)
{
int i;
for(i=l; i<=100; ++i)
printf(''%d //2 is: %f
n", i, (float) i /2);
return 0;
}

28
General forms:
(int) char expression- ordinal value of char
expression
(char) int expression- character with the
ordinal value of int
expression
(int) float expression- truncates the float
expression
(float) int expression- converts int to float
(double) float exp- converts float to
doublehttp://improvec.blogspot.in

Data type

More Related Content

What's hot (20)

Viewers also liked (20)

Similar to Data type (20)

More from myrajendra (20)

Recently uploaded (20)

Data type