Computing EnvironmentsCSC8304

Marcus Kaiser

http://www.biological-networks.org

About this module

Module Leader: Dr Marcus Kaiser

Today’s lecture – Introduction to Computing Environments

Lectures for the next 4 weeks cover the need for database systems, statistical packages, security and poll-based/event-driven software

Reading Week then follows – no lecture

Remaining lectures cover programming languages, scripting and Perl Lectures are on Tuesdays, 9:30-11am, CLT.602 Lecture notes can be found on http://www.biological-networks.org/ (Training > Computing Environments for Bioinformatics )

Practical classes start in DAYSH.821 and are on Wednesdays 11-12am

Assessment

Coursework

Databases/SQL 5 Nov deadline 15% of final mark

Scripting/Perl 10 Dec deadline 15% of final mark

Exam

Exam January 70% of final mark

A computing environment

Requirements

Services

Enabling presentation of services to users and interaction with such services by users

Mobile devices (e.g., mobile phones)

Video game consoles Printers

Tactile feedback devices

Monitors

A world of supporting

services

Robots

A heterogeneous environment

A modern day computing environment is made up from many different types of enabling technologies.

An enabling technology refers to the mechanism that is used to implement a service.

Many technologies share the same ultimate goal (e.g., sending a message from one computer to another).

However, such technologies may attempt to achieve the same goal in different ways (e.g., Microsoft and Linux operating systems).

Standards

There are instances when vendors must adhere to some standard to ensure integration (the Internet protocols exemplify this).

Standards play a crucial role in computer system development. There are two types of standard:

Provided by an organisation that is recognised by the community as assuming the role of identifying standards (members of such an organisation are usually drawn from different vendors).

Provided by a vendor (or group of vendors) and deployed without international recognition (however, such recognition may occur at a later date).

Computer technology evolution

1945: ENIAC http://en.wikipedia.org/wiki/Eniac

2004:Pentium

Complexity 18,000 Valves X 103 42 M transistors

Size 200 m3 X 10 -8 6 cm3

Speed 150 ops/s X 106 1.6 x 109 ops/s

Consumption 10 kW X 10-3 68W

Cost $10 000 000 X 10-4 <£1000

Reliability Hours X 1000 Years

What if cars improved in a similar fashion?!!

Speed 70 mph X 106 11000km/s

Fuel 50 mpg X 10-3 50,000 mpg

Cost £10,000 X 10-4 £1

Reliability 1 Year X 1000 1000 Years

Weight 1 ton X 10-8 10 mg

Conceptual Levels of Computers

A digital computer is capable of computation, communication and storage.

Computation is performed by carrying out instructions, a sequence of instructions to solve a problem is called a program

Instructions are recognised and executed by the electronic circuits in the computer

Instructions can only permit simple operations, typically, they can: Add two numbers Check if a number is zero Move data around in Memory

This set of instructions is called the machine language Different types of computers usually have different machine

languages The machine language is said to be the interface between the

software and the hardware.

Conceptual Levels of Computers contd.

Most users do not use machine language Use high level language e.g. Java The high level language is

translated to machine language by a compiler

Computers can be thought of as having different levels, each with its own language.

Each level carries out tasks on behalf of the level above it.

Helps to cope with understanding the complexity of computing systems

Software

Software and/orHardware

Hardware

Assembly Language Level(Assembly programmer)

Conventional machine level(hardware designer)

Integrated circuit level(VLSI designer)Transistor level

(Physical designer)Silicon + electronics level

Chemical engineer

Application Software(anybody)

High Level Language(Java programmer)

Operating System Level(programmer)

Data Representation (1)

Humans count in base 10, using 10 digits Difficult to represent electronically Machines count in base 2 Two-state devices are easy to make (transistors) Only two digits used (0 and 1) called binary digits or bits Electrically represented by 0 volts and 5 volts Each bit occupies one memory cell or wire The basic working unit consists usually of 8 bits, called a byte The basic memory unit is a multiple number of bytes e.g.

2 bytes = 16 bits 4 bytes = 32 bits 8 bytes = 64 bits The basic memory unit is called the word length

Data Representation (2)

All bytes in the memory are numbered, or addressable The first byte is numbered 0, the second 1, and so on Memory size is usually expressed in terms of (Mega)bytes It is common practice to:

Write the least significant bit (LSB) on the right Write the most significant bit (MSB) on the left Start counting from zero

All data held within the computer is represented by a number of bits or bytes

All high level objects, such as a Java or C++ class must be translated into bits

Data Representation (3)

Data comes in many forms Booleans Characters (i.e. text) Integers, both positive and negative; e.g. -230, -1, 0, 45319 Real numbers, also called floating point numbers, e.g. 3.0, log

(13), sin(π/4), 22/7

Structured data types defined by programming languages e.g. Arrays Strings Classes

Each type is represented by one or more bits

Bits, Bytes, and Buzzwords

Byte Kilobyte (KB) Megabytes (MB) Gigabytes (GB) Terabytes (TB)

= 8 bits

= 1024 (210) Bytes

= 220 Bytes

= 230, or about a billion, Bytes

= 240, or about a trillion, Bytes

Terms used to describe file size or memory size:

Integer data Integer numbers don’t allow fractions Humans use the decimal number system. There are 10 digits, 0 –

9. Each place within a decimal number represents a power of 10.

For example 236 = 2 * 102 +3 * 101 +6 * 100 +

10 is not a ‘natural’ base (it is an anatomical incident!) Computers work more naturally with base 2 because transistors

have two states In base 2, only digits 0 and 1 are used. Greatly simplifies the

arithmetic and makes it much faster

Binary Numbers

Each place within a binary number represents a power of 2. e.g binary 101 =

1 x 22 + 0 x 21 + 1 x 20

(equals five in decimal) Electrical representation: three wires

ON OFF ON

(5V) (0V) (5V)

Binary Arithmetic Humans perform decimal addition by:

Memorising all single-digit additions Writing the numbers to be added down right-aligned, one above the

other Starting at the right and working towards the left Adding the digits, writing down the result and propagating any carry

to the next column

Subtraction works much the same way except that you must borrow from the next column

Multiplication with a single-digit number works much the same way too

Multiplication with a multi-digit number is treated as a series of separate single digit multiplications, the results of which are added together

Binary addition, subtraction and multiplication can treated exactly the same except that only the digits 0 and 1 are used.

Basic Binary Arithmetic - examples

1 0 0 1 0 1 0

0 0 1 1 1 0 1 +

- - - - - - -

1 1 0 0 1 1 1

0 0 1 1 0 1 0

0 0 0 1 0 0 1 -

- - - - - - -

0 0 1 0 0 0 1

Hexadecimal Numbers

Problem with binary arithmetic – Long strings are fine for machines but awkward for humans

e.g. What is the binary number 0100101011100011 ?? Guess then work it out!

We (humans) therefore often use hexadecimal numbers (or hex for short).

This uses base 16. There are 16 “digits” (0 1 2 3 4 5 6 7 8 9 A B C D E F) Each place represents a power of 16:

e.g. 29F = 2 * 162 + 9 * 161 + F * 160 (=671 in decimal)

Integer Representation

For the sake of economy, different hardware representations are used to implement different integer ranges

The following are commonly found:

Name Bits Range signed Range unsigned

Byte 8 -128 … 127 0 .. 255

Word 16 -32768 .. 32767 0 .. 65535

Long 32 -231 .. 231-1 0 .. 232-1

Quad 64 -263 .. 263-1 0 .. 264-1

Integer overflow

It is possible that the result of an integer calculation is bigger than the allowed maximum (both positive and negative)

Look at the following 8-bit addition

11001000 200 -5610010110 150 -106-------------- ----- ------

(1)01011110 (256+) 94 (-256+) 94 The final carry “disappears” because there is no hardware provision for it. The problem is

called overflow (or underflow)

Is this serious? Would you like this to happen to your bank account?

Overflow is a serious problem. It indicates the presence of a bug in your program. The hardware can detect overflow and will cause your program to crash

Overflow occurred in the European Space Agency’s Ariane 5 rocket when the on-board software attempted to fit a 64 bit number into 16 bits. This did indeed cause the program to crash...

Floating Point data

The range of possible values using 32 bits to represent a number, positive or negative, is large

However, bigger number representations are needed. e.g. numbers to allow fractions and powers as required by

many scientific applications To represent fractions using integers, you would need two of

them One for the numerator and one for the denominator Would be a major nuisance – not computationally amenable

The way to do this is to use floating point numbers. Floating point data types allow a much greater range of possible

values They are represented in floating point notation

Floating Point Notation

Details of how floating point values are represented vary from one machine to another.

The IEEE standard is one of the standard floating point representations

More info at http://www.cs.uaf.edu/~cs301/notes/Chapter4/node13.html

Character Data

Used for textual data, but can represent small integers Usually held in a byte although commonly only 7 bits are needed There are two major character sets:

EBSIDIC (on IBM mainframe machines) ASCII (on all other machines)

We concentrate on ASCII (American Standard Code for Information Interchange)

It has been standardised by ISO (International Standardisation Organisation)

ASCII was actually designed for use with teletypes and so the descriptions are somewhat obscure

Often ‘text’ documents are referred to as in ‘ASCII’ format – easier for document interchange

ASCII

The characters are classed as Graphic characters (printable or displayable symbols) Control characters (intended to be used for various control

functions, such as vertical motion and data communications. The basic ASCII set uses 7 bits for each character, giving it a

total of 128 unique symbols. The extended ASCII character set uses 8 bits, which gives it an

additional 128 characters. The extra characters represent characters from foreign

languages and special symbols for drawing pictures.

More info @ http://www.jimprice.com/jim-asc.htm

Unicode

Unicode is a new system to standardise character representation

Unicode provides a unique number for every character, independent of platform, program, or language

Adopted by such industry leaders as Apple, HP, IBM, JustSystem, Microsoft, Oracle, SAP, Sun, Sybase, Unisys.

Required by modern standards such as XML, Java, ECMAScript (JavaScript), LDAP, CORBA 3.0, WML

An implementation of the ISO/IEC 10646 standard Enables Internationalization

Unicode

How Unicode Works It defines a large (and steadily growing) number of characters (>

110,000). Each character gets a name and a number, e.g. LATIN

CAPITAL LETTER A is 65 and TIBETAN SYLLABLE OM is 3840.

Includes a table of useful character properties such as "this is lower case" or "this is a number" or "this is a punctuation mark".

The Unicode standard also includes a large volume of helpful rules and explanations about how to display these characters properly, do line-breaking and hyphenation and sorting

Unicode is important – do some extra reading! – try a Google search

Summary

A modern day computing environment is made up from many different types of enabling technologies

Standards are used to permit interoperability

Computers can be thought of as a number of different levels, ranging from the application software that we all use, right through to the electronic circuits within the computer

Computers count in binary

Various ways of representing numeric and character data