Basic/Primitive Types

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This post is part of my ongoing effort to familiarize the readers with the commonalities & variabilities of C++/Java/C# programming languages. A tentative outline of this series can be found at Contents.

In a previous post Identifiers, I have discussed identifiers that we can write in the source. Type restricts the identifier to size & kind of data and in addition, the operations that can be performed on that data. Both Java and C# support almost all basic data types of C++ but change characteristics of some. C++/Java/C# are strongly typed languages meaning each object must have a predefined data type.

Type Modifier:
C++ has 7 basic data types. They are int, float, double, bool, char, wchar_t, void. It uses four type modifiers to restrict the signedness and size of data that can be stored on a data type identifier -

1. signed: Defines a positive (+ve) or negative (-ve) type. All types are implicitly positive.
2. unsigned: A positive (+ve) type. Variable of this type can't hold negative values.
3. short: Types are implicitly short if not otherwise specified.
4. long: Extends the size of basic type to holder larger value.

.Net programs are compiled into Microsoft Intermediate Language (MSIL). Similar to Java Byte Code, it is  independent of hardware architecture and is translated to machine code during or before execution. But unlike Java, it brings a common type system (CTS) which means the actual program can be written in arbitrary language which can compile for .Net and the respective compiler is responsible for translating it to MSIL. MSIL defines a set of data types and each .Net compatible compiler must translate its own data types to the corresponding data types in MSIL. In other words, each data type in C# resembles a data type in MSIL.

In Java and C#, the primitive types are value types (more in Value Type vs. Reference Type and Boxing vs. Unboxing) which are allocated in the stack and copied during assignment. There are corresponding reference types in both the languages with implicit conversion from each other. The boxed types of Java are listed in "Java Boxed" and that of C# are in ".Net Type" columns.

Following is a list of the primitive data types in these languages. The sign "-" means the type is not directly supported by some particular language and the type in bracket beside it shows what can be used as a replacement.

C++

Java

Java Boxed

C#

.Net

- (unsigned char)

- (byte)

- (Byte)

byte (8)

Byte

- (signed char)

byte

Byte

sbyte (8)

SByte

int

int(32)

Integer

int (32)

Int32

unsigned int

-

-

uint (32)

UInt32

short
(short int)

short

Short

short (16)

Int16

unsigned short

-

-

ushort (16)

UInt16

long (long int)

long (64)

Long

long (64)

Int64

unsigned long

-

-

ulong (64)

UInt64

float

float

Float

float (32)

Single

double

double

Double

double (64)

Double

wchar_t

char

Character

char (16)

Char

bool

boolean

Boolean

bool (8)

Boolean

- (void*)

Object

Object

object

Object

-

-

decimal (128)

Decimal

- (std::wstring)

java.lang.String

java.lang.String

string

String

Type Qualifiers
Further keywords are used to guarantee data safety or specify data vulnerability. const

C++

Java

C#

.Net

const

final

const

-

-

-

readonly

-

volatile

-

volatile

-

Storage Class Specifiers
Further keywords are used to guarantee data safety or to specify data vulnerability.

C++

Java

C#

.Net

auto

-

-

-

register

-

-

-

static

-

-

-

extern

-

extern

-

Variables

A variable has a name and we keep some information in it. The information can be altered afterward, hence the name variable. C++/Java/C# are strongly typed languages which means each variable has a defined type i.e. you cannot assign value of a type to a variable of another type.

int textLength = 0; //defines a variable of integer type
float average = 1.0; // defines a variable of float type 

Function (aka method/routine/subroutine/operation/procedure) Names

A function or method defines a particular responsibility of the program. It has a return type and a set of parameters.

/*Add two integers and return the result*/
int doSum(int x, int y)
{
    return x + y;
}

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