CSS307-System ProgrammingSuleyman Demirel University

Fall 2015by Konstantin Latuta & EN3[ABCD]04

Summary of week 1, 2 and 3

Outline

● Big picture of relevant knowledge areas● Hardware organization of computer system● Operating system concepts● UNIX history and concepts● Introduction to Linux● Why to study System Programming● Grading policy and syllabus

UNIX/Linuxsystem programming

computer organization& architectureoperating systems

concepts

working knowledgeof UNIX/Linux

and C programming

relevant knowledge areas

our class

Hardware Organization of Computer System

A modern computer system by A. Silberschatz et al, “Operating Systems Concepts: Essentials”

Hardware Organization of Computer System

Hardware Organization of Computer System

● Buses– collection of electrical conduits that carry bytes of information back

and forth between the components

– transfer fixed-sized chunks of bytes known as words, for example 32 bits or 64 bits

● I/O devices– Keyboard, mouse, display, disk drive, network adapter

Hardware Organization of Computer System

● Main memory– temporary storage device that holds both a program and the data it

manipulates while the processor is executing the program

– DRAM

● Processor (Central Processing Unit)– the engine that interprets (or executes) instructions stored in main memory.

– contains a set of registers that helps it operate

– Arithmetic Logical Unit inside the CPU operates on registers and stores a result back to registers

The truth about memory...

Cache...

Computer system is not just hardware

Operating Systems Concepts

● OS has 2 main goals– To protect the hardware from misuse by application programs...

– To provide applications with simple and uniform mechanisms for manipulating complicated and often wildly different low-level hardware devices

● The goals are achieved by several abstractions– processes, virtual memory and files

Abstractions provided by operating system

Process

● A process is the operating system’s abstraction for a running program– Illusion of exclusive use of the processor, main memory, and I/O

devices

Virtual Memory

● An illusion provided to process that it has an exclusive use of the main memory.– each process has a uniform view of

memory called virtual address space

Files

● A file is a sequence of bytes, nothing more and nothing less– every I/O device, including disks, keyboards, displays, and even

networks, is modeled as a file

UNIX OS

● A multi-user and multi-tasking operating system that dates back to 1969 at AT&T Bell Labs.– multi-user: when two or more people can work on the same computer at the

same time, using different terminals● A terminal is a device with a monitor and a keyboard. (The concept is more complex

than this, but for now think of it this way. There are also special windows called pseudo-terminals.)

– multi-tasking: when two or more programs can be running on the computer at the same time

● but it does not mean there has to be more than one processor; programs may timeshare the processor

Why all the fuss about UNIX?

● UNIX is a professional operating system that lets you do sophisticated tasks easily

● It lets you customize your work environment and create new commands

● It is inherently very secure because of the way it was designed● Linux is a UNIX-like operating system that is very popular

Why UNIX became popular?

● Portable– because it was written mostly in C (a new idea for that time)

● Very small– 10,000 lines of C, and about 1,000 lines of assembler

● Free– it was distributed to universities and research laboratories for free by AT&T

● Innovative– it had many features that were not part of any other operating systems such as

shells, pipes, files etc.

User interfaces

● Graphic User Interface (GUI)● Command Line Interface (CLI)

– shell is a program that uses terminal device to bridge user and kernel

– kernel is the main part of any OSthat controls hardware etc.

kernel shell

A word to creators of UNIX

● The success of UNIX lies not so much in new inventions but rather in the full exploitation of a carefully selected set of fertile ideas, and especially in showing that they can be keys to the implementation of a small yet powerful operating system.– Ken Thompson, Dennis Ritchie

● fertile ideas– files and file hierarchy, processes, users and groups, priviledged and

non-priviledged instructions, environments, device independent input/output...

Linux OS

● Linux is a free open source operating system initially intended for Intel x86-based PCs

● 1991, Linus Torvalds, a student in Helsinki started writing his own OS kernel, known as Linux kernel

● 1992, Linux was re-licensed with General Public License (GPL) by GNU (a project of Free Software Foundation which promotes free software)

● Mid-90s, Linux distributions emerged● 1998, major companies announced support

Linux Philosophy

● Linux is a free and open source version of UNIX● Linux is maintained by a network of developers from all

over the world● Hierarchical filesystem with the top node / (aka root)● Everything is a file (or a file-like object)● Fully multitasking and multiuser OS

https://www.youtube.com/watch?v=H7Uz692S6T4https://www.youtube.com/watch?v=RaFNXQ8Dat0https://www.youtube.com/watch?v=_C-GAkLPAAc

Linux Distributions

● Linux kernel is the core of a computer operating system (www.kernel.org)

● Linux distribution = kernel + some software tools– File management, user management, software package management

tools

● commercially supported distributions: Red Hat, SUSE, Ubuntu● free: CentOS, Fedora, Ubuntu, openSUSE● And many others like Scientific Linux, Oracle Linux etc.

Distro Families

Debian Family Key Facts

● The Debian family is upstream for Ubuntu, and Ubuntu is upstream for Linux Mint and others.

● The Linux kernel 3.13 is used in Ubuntu 14.04.● It uses the DPKG-based apt-get package manager

(we cover in more detail later) to install, update, and remove packages in the system.

● Ubuntu has been widely used for cloud deployments.● While Ubuntu is built on top of Debian, it uses the

Unity graphical interface, is GNOME-based and differs quite a bit visually from the interface on standard Debian as well as other distributions.

Fedora Family Key Facts

● The Fedora family is upstream for CentOS, RHEL, and Oracle Linux.

● The Linux kernel 2.6.32 is used in RHEL/CentOS 6.x● It supports hardware platforms such as x86, x86-64,

Itanium, PowerPC, and IBM System z.● It uses the RPM-based yum package manager (we

cover in more detail later) to install, update, and remove packages in the system.

● RHEL is widely used by enterprises which host their own systems.

SUSE Family Key Facts

● SUSE Linux Enterprise Server (SLES) is upstream for openSUSE.

● The Linux kernel 3.11 is used in openSUSE 12.3.● It uses the RPM-based zypper package manager

to install, update, and remove packages in the system.

● It includes the YaST (Yet another System Tool) application for system administration purposes.

● SUSE is widely used in the retail sector.

System Programming

● System programming is the practice of writing system software● System software lives at a low level, interfacing directly with the

kernel and core system libraries● Kernel is the only software that runs all the time on computer

– it is the core of operating system with everything else being system or application software

Why to learn system programming?

● System programmers develop an acute awareness of the hardware and the operating system on which they work

● Application programmers write in Java, JavaScript etc. but someone still has to write the JavaScript interpreter and the Java VM

● Developer writing Python or Ruby or Scala can still benefit from knowledge of system programming, as an understanding of the soul of the machine

Grading Policy and Tentative Syllabus

● 40% Labs and Quizzes● 20% Midterm exam● 20% Final Exam● 20% creative t-shirt project● Portal View:

– 30% = L&Q/2 + M/2

– 30% = L&Q/2 + M/2

– 40% = F + t-shirt

References

● Operating Systems Concepts Essentials, 2nd edition, Abraham Silberschatz et al., 2014

● Computer systems: a programmer’s perspective, Randal E. Bryant, David R. O’Hallaron, 2nd edition, 2011

● UNIX Application and System Programming lecture notes, Steward Weiss, 2013

● Linux Foundation course on edX.org● Linux System Programming, 2nd edition, Robert Love, 2013● Understanding UNIX/Linux programming, Bruce Molay, 2003