UNIX V/s Linux

Sun's Solaris, HP's HP-UX and IBM's AIX are the most popular UNIX flavors available today. They are licensed versions of UNIX and are having a significant amount of cost. Technical support is also available. On the other hand Linux is a free software alternative to the commercial flavors of UNIX and are available without any cost. But do not have a standard technical support mechanism.

Commercial versions are standard considering the requirement, development, testing and support. So each release is consistent. But Linux is very inconsistent compared to UNIX.

UNIX flavors are targeted to particular hardware architecture. But Linux is supposed to be compatible as possible.

Source code of Linux kernel is available. UNIX flavors are available as binary only. They are not modular as Linux.

File system support is limited in UNIX. But Linux supports almost all file systems.

Core applications present in UNIX and Linux are similar. Most of the open source applications are available in Linux. And these are ported to UNIX as well. But enterprise-level applications and closed-source applications will not be present in Linux but can be in UNIX.

Symbian Class naming convensions

Naming convension for classes helps to identify the behaviour of a class
In symbian Prefixes lile T, C, M, R has been used

T Class
Built in types.
Must not have a destructor.
eg: TInt, TBool

C Classes
Derived from CBase
Objects of a C class must always be allocated on the heap.

M Classes
Abstract interface class.
It is used to define callback interfaces or observer classes.
It has no member data and no constructor.

Static Classes
Do not have a name prefix.
Member functions can be called using scope resolution operator.

Symbian Class naming convensions

Naming convension for classes helps to identify the behaviour of a class
In symbian Prefixes lile T, C, M, R has been used

T Class
Built in types.
Must not have a destructor.
eg: TInt, TBool

C Classes
Derived from CBase
Objects of a C class must always be allocated on the heap.

M Classes
Abstract interface class.
It is used to define callback interfaces or observer classes.
It has no member data and no constructor.

Static Classes
Do not have a name prefix.
Member functions can be called using scope resolution operator.

IMPORT_C and EXPORT_C

IMPORT_C should precede the declaration of a DLL function which is to be imported into an application.

EXPORT_C should preced the implementation in C++ source of a DLL function which is to be exported.

Symbian's UI environments

Eikon-Symbian's UI environment.
Uikon-Eikon with Unicode support. Eikon was replaced in v5.1 by Uikon and device specific
Libraries.
Avkon- Nokia series 60 Ui libraries
Qikon-Sony erricson Ui libraries
Ckon- Nokia Communicator 9200 Ui libraries

OSI Reference Model

OSI is an abreviation of Open System Interconnection.
It has got a seven layer architecture.
Layer 1: Physical Layer
It defines the physical, mechanical and electrical charecteristics such as voltage, current, transmission distance, physical connectors etc.
Layer 2: Data Link Layer
Data Link Layer is devided into two. LLC(Logical Link Control), MAC(Mediam Access Control)
Layer 3: Network Layer
Routing related informations
Layer 4: Transport Layer

Layer 5: Session Layer
Layer 6: Presentation Layer
Layer 7: Application Layer