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UNIX for Dummies Questions & Answers
UNIX basics
Post 302920668 by DGPickett on Friday 10th of October 2014 05:23:54 PM
10-10-2014
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.
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.
Last edited by DGPickett; 10-10-2014 at 06:31 PM..
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LEARN ABOUT HPUX
crt0_ia
crt0_ia(3) Library Functions Manual crt0_ia(3) NAME
crt0_ia: crt0.o - execution startup routines for Integrity systems SYNOPSIS
Remarks This manpage describes for Integrity systems. For on PA-RISC systems, see crt0_pa(3). DESCRIPTION
The C, aC++, and FORTRAN compilers link in the object file for statically-bound programs to provide startup capabilities and environments for program execution. It contains startup code that must be linked using to every statically-bound program. In a dynamically linked program (the default method), the object file is not used, and all actions normally associated with it are instead done by the dynamic loader dld.so(5). processes initializers and terminators. Initializers are routines that are called before the program entry point and terminators are rou- tines that are called when the program terminates via the routine. Initializers are invoked in reverse order of the link line so that dependent libraries are initialized before the libraries that depend on them. Terminators, on the other hand, are invoked in the forward order. does not define any variables. It, however, sets the following global variables: A variable of type long containing the number of arguments. An array of character pointers to the arguments themselves. An array of character pointers to the environment in which the program will run. This array is terminated by a null pointer. A variable of type long containing the system id value for an executable program. A variable of type long containing the requested thread local storage size. This variable is initialized with data from the ker- nel. A variable of type void * containing load information passed from the kernel. A variable of type void * whose value equals to the global pointer. A symbol named is also declared in as an enumeration constant, and is incompatible with the declaration in In order to include both header files, it is necessary to define the macro before including This will force the header file to omit the conflicting definition of The enumeration constant is equivalent to in that context, and may be used instead. See ttrace(2). AUTHOR
The features described in this entry originated from AT&T UNIX System III. FILES
SEE ALSO
System Tools aCC(1) invoke the HP-UX aC++ compiler cc(1) invoke the HP-UX C compiler dld.so(5) the dynamic loader exec(2) execute a file f90(1) invoke the HP-UX FORTRAN compiler ld(1) invoke the link editor Miscellaneous end(3C) symbol of the last locations in program Integrity Systems Only crt0_ia(3)