Fundamental Data Types

1
Fundamental Data Types
2
Declaration

• All variables must be declared before being used.
• Tells the compiler to set aside an appropriate
  amount of space in memory to hold values
  associated with variables.
• 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
• The char type can be modified
• char signed char unsigned char

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

0
0
0
0
1
1
0
1
6

• String of binary digits are called bit strings.
• A bit string is interpreted as a binary number.
  bnbn-1b2b1b0
• 0 1 1 0 0 0 0 1 a
• This bit string has the value
• 1?26 1?25 1?20 97

7

• 3 types
• 1) char 2) unsigned char 3) signed char
• Each uses 1 Byte.
• Typically char is equivalent to either signed or
  unsigned char.
• Signed char -128 to 127
• Unsigned char 0 to 255

8
Data Type int

• INTEGERS Include the natural counting numbers
  and their negatives.
• INTEGRAL DATA TYPES
• int short long unsigned

9

• The magnitude of the number that an int variable
  can hold depends on ___________?
• The range, u, of values
• 2wordsize-1 ? u ? 2wordsize-1-1
• 2 Byte word -32 Thousand To 32
  Thousand
• -215, -2151, , -3, -2, -1, 0, 1, 2, 3, ,
  215-1
• 4 Byte word -2 Billion To 2 Billion
• -231, -2311, , -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, -2151, , -3, -2, -1, 0, 1, 2, 3, ,
  215-1
• long - needed for larger integers (usually 4
  
• bytes).
• -2 Billion To 2 Billion
• -231, -2311, , -3, -2, -1, 0, 1, 2, 3, ,
  231-1

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, , 232-1

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
The Floating Types

• float double long double
• Hold Real Values.
• 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).

15

• Notation exponential 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 lt 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.

17
Internal Representation

• FLOAT
• 01 8 9 31
• SEEEEEEEE FFFFFFFF
• DOUBLE
• 01 11 12
  63
• SEEEEEEEEEEE FFFFFFFFFFF

18

• Float
• Precision 6 significant digits.
• Range 10-38 to 1038
• 0.d1d2d3d4d5d6 ? 10n
• di is a significant digit , N is range.
• Double
• Precision 15 significant digits (252 ? 1015)
• Range 10-308 to 10308 (2-2048 to 22047)
• 0.123451234512345 ? 103 (15 sig. digits)

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
Compile-Time Operator sizeof

• 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

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 primarily helps to generate portable code
  that depends upon the size of the built-in data
  types.

/ Write 6 integers to a disk file. /void put_re
c(int rec6, FILE fp)  int len  
len  write(fp, rec, sizeof(int)6)  if(len ! 1
) printf(''Write Error")0
23

• sizeof(char) 1
• sizeof(short) ? sizeof(int)
• ? sizeof(long)
• sizeof(signed) sizeof(unsigned)
• sizeof(int)
• sizeof(float) ? sizeof(double)
• ? sizeof(long double)

24
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)

25
char ch int i float f double d result (ch /
i) (f d) (f i) int
double float int
double float
double
26
Casts

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

(float) i/2
27

• 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

28
/ print i and i/2 with fractions / int main(void
)   int i   for(il ilt100 i)  
  printf(''d // 2 is f\n", i, (float) i /2)
return 0
29

• 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
  double