What is portability?

Answer 1

Portability is a characteristic attributed to a computer program if it can be used in an operating systems other than the one in which it was created without requiring major rework. Porting is the task of doing any work necessary to make the computer program run in the new environment. In general, programs that adhere to standard program interfaces such as the X/Open Unix 95 standard C language interface are portable. Ideally, such a program needs only to be compiled for the operating system to which it is being ported. However, programmers using standard interfaces also sometimes use operating system extensions or special capabilities that may not be present in the new operating system. Uses of such extensions have to be removed or replaced with comparable functions in the new operating system. In addition to language differences, porting may also require data conversion and adaptation to new system procedures for running an application. Portability has usually meant some work when moving an application program to another operating system. Recently, the Java programming language and runtime environment has made it possible to have programs that run on any operating system that supports the Java standard (from Sun Microsystems) without any porting work. Java applets in the form of precompiled bytecode can be sent from a server program in one operating system to a client program (your Web browser) in another operating system without change.

Answer 2

"Portability" means writing your program (code) in such a way that the same code works on different environments i.e. different processors, different operating systems, different versions of libraries etc. If your program is portable, you should be able to just re-compile it on any new system and it should run without problems. Portability is important because non-portable code causes lots of problems in maintenance - managing multiple versions, poor readability / understandability of the code to name a few. Any good programming book will give guidelines on how to write portable code - avoiding hard-coding, judicious use of compiler directives like #ifdef etc. Hope this helps. - Ramki.

Answer 3

Portability simply refers to whether the source code is machine-dependent or not. Machine-dependent code is non-portable code; it is specific to a particular architecture and/or platform. Machine code and assembly language are examples of non-portable languages.

C and C++ are portable languages because the code can be compiled upon any machine to produce the machine-dependant code. However, both can also be used to write non-portable code if desired, thus you can write operating systems, drivers and embedded systems software as well as application software.

Java is fully portable because it compiles to byte code suitable for interpretation by any Java virtual machine implementation. In other words, you program and compile code specific to the virtual machine rather than to the physical machine, and the virtual machine creates the machine-dependant code at runtime. The downside is that Java cannot be used to write machine-dependent code, so it can only be used to write applications software.