程序代写代做代考 compiler Fortran assembly file system Linux

Linux

UNIX and LINUX
CSE 2421
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Developed from 1969-1971 at AT&T Bell Laboratories (Ken Thompson/Dennis Ritchie/Brian Kernighan/Douglas McIIroy/Joe Ossanna)
Written largely in C (some assembly language code as well)
C was originally developed as a programming language to write the Unix OS, which was a multi-user, multi-tasking OS.
Proprietary (requires a license for use)
AT&T sold Unix to Novell in the early 1990s, which then sold its Unix business to the Santa Cruz Operation (SCO) in 1995
UNIX trademark passed to the industry standards consortium The Open Group, which allows the use of the mark for certified operating systems compliant with the Single UNIX Specification (SUS). Among these is Apple’s MacOS which is the Unix version with the largest installed base as of 2014.
Unix background
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“Modular design”: The OS provides a collection of simple tools that each implement a limited, well-defined function. (This was very forward thinking at the time.)
More complex functionality is provided by combining the simple tools.
A unified file system is the main means of communication; for example, devices (e.g., disk drives, keyboards) are treated as files.
First “portable” operating system
Unix Philosophy
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Developed in 1991 by Linus Torvalds, a graduate student in Computer Science at the University of Helsinki.
Linux is a Unix “clone,” we can say, because it does not use Unix code (which is proprietary, and therefore could not be freely distributed), but it provides the same functionality and features as Unix generally, and follows the Unix OS philosophy.
Open source, so it is available in versions without cost (There are also versions which are licensed for a fee, often with support, as well as the OS itself)
Various “distributions,” which are all broadly similar, but also exhibit various differences.
It is worth your time and effort to learn as much as you can about Linux, because you are likely to encounter Linux/Unix in the work world.

Linux
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http://tldp.org/LDP/intro-linux/html/sect_01_01.html
This link comes from: https://cse.osu.edu/computing-services/getting-help under the External Resources section “Introduction to Linux”
http://www.diffen.com/difference/Linux_vs_Unix

Required Reading
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“Unix is used by 70.3% (up from 68.9% last January) of all the websites whose operating system we know..”
Linux is used by 52.2% (down from 53.9% last January) of all the websites whose operating system we know. (This 52.2% is a part of the 70.3% aggregate above.)
http://w3techs.com/technologies/details/os-unix/all/all

Linux also runs on 96-98% of the top 500 supercomputers!

Has anyone used a Raspberry Pi??? Then you use Linux

Some facts about current Linux usage
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No code to write
Some (short) articles to read
Some navigation within a Linux command line window
Compiling C programs
Some experience using the gdb debugger
How to zip files (many may already know)
How to submit to Carmen from stdlinux

Lab 1 assignment
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By convention, C source code files in a Unix/Linux environment have a .c “extension” (It isn’t really an extension in Unix/Linux, and the OS does not need it; the source code file is just a text file, and the OS can identify it as a text file without the .c).

Source code
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Located as a file call lab1.c on Carmen; it’s also documented in the Lab 1 Description document

Type in the file exactly as it is.
Don’t use copy/paste. You will likely get a few unprintable characters in your .c file that will cause problems.
e.g., Windows treats the ‘\n’ differently from Linux

Source code
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After you enter the complete source code as specified in the Lab 1 description document, save the file from within the text editor!
You can leave the text editor open, and enter commands on the Linux command line (if you used ‘&’ when you opened the text editor).
After saving, you can compile the source code as follows:
% gcc -ansi -pedantic –g -o lab1 lab1.c

Saving and compiling
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The gcc compiler collection can be used to compile, or more technically, build, C source code under a number of different standards, including ANSI C (sometimes called C89), C90, or C99
In this class, we will learn ANSI C, or C89, which is actually the same standard as C90 (but the two were published separately, and that’s why there are two distinct names, even though there is only a single standard).
When you build/compile code for any C language lab in this class, you must build it with the -ansi -pedantic options, so that you will get warnings about code that does not comply with the C89/C90 standard (the -pedantic option does this).
The graders will build your code this way. ANY lab code that, when compiled as above, generates any errors or warnings, even if it builds successfully (that is, even if there are no syntax errors which prevent compilation) will receive NO POINTS.
The –g option is used when we plan to use the executable with the debugger, gdb (in our example).
Note on -ansi -pedantic
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A large percentage of industry environments still use ANSI C (C89/C90), so it’s important to learn this standard, and that’s why we use it in this course.
For this reason, in terms of portability, writing ANSI-compliant C code is important also. (Employers like this.)
Learning the differences later between ANSI C and another standard, say C99, is not too difficult if you need to do it later.
Importance of the standards
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Learning how to use the debugging program, gdb, will make your life in this class significantly easier. As well, make you more marketable.
You can watch your program run instruction by instruction
You can observe a variable change values and see when things you thought wouldn’t happen.
Then you have opportunities to fix them within your code with significantly less effort than staring at your code into the wee hours of the morning.

Running the program with gdb
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gdb(1) GNU Tools gdb(1)

NAME
gdb – The GNU Debugger

SYNOPSIS
gdb [-help] [-nx] [-q] [-batch] [-cd=dir] [-f] [-b bps] [-tty=dev] [-s symfile] [-e prog] [-se prog] [-c core] [-x cmds] [-d dir] [prog[core|procID]]

DESCRIPTION
The purpose of a debugger such as GDB is to allow you to see what is going on ‘‘inside’’ another program while it executes—or what another program was doing at the moment it
crashed.

GDB can do four main kinds of things (plus other things in support of these) to help you catch bugs in the act:

· Start your program, specifying anything that might affect its behavior.

· Make your program stop on specified conditions.

· Examine what has happened, when your program has stopped.

· Change things in your program, so you can experiment with correcting the effects of one bug and go on to learn about another.

You can use GDB to debug programs written in C, C++, and Modula-2. Fortran support will be added when a GNU Fortran compiler is ready.

Check out Figure 3.39 in Computer Systems: A Programmer’s Perspective, 3rd Edition (page 280)

GDB – Debugger on CSE Server
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ddd(1) GNU Tools ddd(1)

NAME
ddd – The Data Display Debugger

SYNOPSIS
ddd [–help] [–gdb] [–dbx] [–ladebug] [–wdb] [–xdb] [–jdb] [–pydb] [–perl]
[–debugger name] [–[r]host [[username@]hostname]] [–trace] [–version] [–config-
uration] [options…] [prog[core|procID]]

but usually just

ddd program

DESCRIPTION
DDD is a graphical front-end for GDB and other command-line debuggers. Using DDD, you can
see what is going on “inside” another program while it executes—or what another program was
doing at the moment it crashed.

DDD can do four main kinds of things (plus other things in support of these) to help you
catch bugs in the act:

· Start your program, specifying anything that might affect its behavior.

DDD Debugger on CSE Server
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