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2. Primitive data Types
Data types that are not defined in terms of other types
are called primitive data types.
Also called as Built-in data
types.
Examples:
a. Numeric Data Types
(Integer, Floating-Point, Complex, Decimal etc.)
b. Boolean Data Types
C. Character Data Types
a. Numeric Types
i. Integer
For example, Java includes four signed integer
sizes: byte , short , int , and long .
Some languages, for example, C++ and C#, include unsigned
integer types, which are simply types for integer values without signs.
A signed integer value is represented in a
computer by a string of bits, with one of the bits (typically the leftmost)
representing the sign.
Most computers now use a notation called twos
complement to store negative integers.
In
twos-complement notation, the representation of
a negative integer is formed
by taking the logical complement of the positive version of the number and
adding one.
Ones-complement notation is still used
by some computers. In
ones-complement notation, the negative of an integer is stored as the logical
complement of its absolute value.
ii. Floating-Point
Floating-point data types model real numbers.
Most languages include two floating-point types, often
called float and double.
The collection of values that can be represented by a
floating-point type is defined in terms of precision and range.
Precision is the accuracy of the fractional part
of a value, measured as the number of bits.
Range is a combination of the range of fractions
and, more important, the range of exponents.
IEEE floating-point formats:
(a) single precision,
(b) double precision
iii. Complex
Some programming languages support a complex data type.
For example, Fortran and Python.
In Python, the imaginary part of a complex
literal is specified by following it with a j or J —for example,
(7 + 3j).
Languages that support a complex type include
operations for arithmetic on complex values.
iv. Decimal
Most larger computers that are designed to support
business systems applications have hardware support for decimal data types.
Decimal data types store a fixed number of decimal
digits, with the decimal point at a fixed position in the value.
COBOL, C# and F# languages have decimal data types.
Decimal types are stored very much like character
strings, using binary codes for the decimal digits. These representations are
called binary coded decimal (BCD).
b. Boolean Types
Their range of values has only two elements: one for true
and one for false.
They were introduced in ALGOL 60 and have been
included in most general-purpose languages designed since 1960.
c. Character Types
Character
data are stored in computers as numeric codings. Traditionally, the most
commonly used coding was the 8-bit code ASCII (American Standard Code for
Information Interchange), which uses the values 0 to 127 to code 128
different characters.
Because of the globalization of business and the need
for computers to communicate with other computers around the world, the ASCII
character set became inadequate. In response, in 1991, the Unicode
Consortium published the UCS-2 standard, a 16-bit character set.
This character code is often called Unicode.
Unicode includes the characters from most of the
world’s natural languages.
For example, Unicode includes the Cyrillic alphabet,
as used in Serbia, and the Thai digits.
After 1991, the Unicode Consortium, in cooperation with
the International Standards Organization (ISO), developed a 4-byte character
code named UCS-4, or UTF-32, which is described in the ISO/IEC 10646
Standard, published in 2000.
The first 128 characters of Unicode are identical to
those of ASCII.
Java was the first widely used language to use
the Unicode character set. Since then, it has found its way into JavaScript,
Python, Perl, C#, and F#.
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