UNIX for Dummies Questions & Answers

Hi,
I am new to Unix.
can you explain in brief with examples what is variable, what is argument and what is parameter?
i searched a lot on other forums but not able to find a appropriate answer.
thanks in advance!!

There is a relationship between arguments and parameters.
Given the function

Code:

foo() {
echo "$1"
echo "$2"
}

You can call the function with two arguments

Code:

foo hello world

In the function the arguments hello and world appear in the parameters $1 and $2.

Your question is too vague to sensibly answer. There's no "UNIX kind" of variable. UNIX has lots of things with lots of kinds of variables.

MadeInGermany's answer assumes you are asking about shell script, which is not a bad guess, but not 100% certain either.

If you mean in general, not any particular programming language, it's not a UNIX question at all.

A Parameter is an Argument with a stuck up attitude? An Argument is a Parameter with a bad attitude?

Yes, UNIX is an O/S, the variables and such come with languages, applications, the O/S kernel and libraries. UNIX is mostly written in C, or these days maybe C++, and comes with libraries that are most accessible in those languages. Other languages wrote interfaces to them. Since libraries are in execution or object code, any language can link to them and pass and receive data, sometimes with other real world side effects like writing a file.

The shell is a slightly more human friendly, interactive- and interpretation-oriented language. There are many variations on the shell.

Variables exist in the memory space of the application's process and in the UNIX kernel. They usually conform to datatypes of the common languages and CPU hardware, like the 4 byte or 32 bit 2's complement big-endian signed binary integer, or int. All memory and file space is alike until a context is thrown over it. If it is string or character data, still the glyphs you see when it is prints and the amount of space it takes is context-dependent: ASCII, EBCDIC, UNICODE, UTF-8, EUC, Latin-1, iso8859-1, . . . . Memory can have code and variables in it, as well as unallocated spaces. For a compiler or link loader, the code is also just data out of context. Most code is CPU-specific and somewhat O/S specific (object code), but some is for an interpreter like the shell (scripts or *codes) or to instruct a compiler (source code). Source code is text from humans that is compiled into object code for execution. Some programs can be executed directly, and others are just libraries of callable subroutines and other constants to assist runnable programs and each other. The UNIX kernel is the first loaded program at the bottom of memory by bootload, which serves all the running processes, some of which are part of the UNIX O/S.

Knowing the big picture keeps the snow level down. Everything runs on top of this, one way or the other. Every O/S is many ways similar.