Transcript Chapter 1
CS 101 History and Basics Brief history • Electronic computers • First ones built in 1940’s • Military uses – projectile trajectories, code breaking (Enigma) • Mainly big calculators • Built on the binary principle – a switch is either on or off (1 or 0) Moore’s Law • Gordon Moore • Engineer • Co-Founder of Intel with Robert Noyce • The “Law”: he observed that the number of transistors on a chip doubled about every two years • It is not a physical law, just a projection of technological advancement • Has held from 1975 until 2012 • Implications for world economy, consumer expectations Computers all around us • The first computers were huge and expensive • Owned mainly by businesses and governments • In the 1970’s computers were reduced in size by the introduction of “microprocessors”. Personal computers like Apple II’s, Commodore, Sinclair, Atari were popular. • Later people bought desktops and then laptops for home use • Around the turn of the 21st century, more electronic devices became popular: ebooks, smart phones, tablets Embedded computers • • • • Many electronic devices have computers inside them Not generally meant for humans to interact with directly Usually are special purpose Examples • Cars, in fact vehicles of all kinds • Dishwashers • Security systems • Medical devices • ATMs Representing information as bits • Computers are based on devices which are in one of two states, on or off. Usually • • • • the on state is called a 1 and the off state is a 0. One of those devices stores a bit (binary digit). This is a very small amount of information, so often bits are grouped into groups of 8, which are called bytes. One byte is big enough to store a number from 0 to 255, or one character like “A” or “3” or “?”. All information in a computer is represented by numbers. That includes characters, colors, sounds, programs, … Character codes • In the early days of computers, every manufacturer had their own code for • • • • • characters (HP, IBM, Sperry, Digital) The users didn’t care as long as they pressed an A on the keyboard and got an A on the screen As time passed, more computers meant more data and more users People wanted to share or buy or sell data with colleagues The incompatibilities in the character codes between hardware makers created a problem Eventually everyone decided that a “standard code” was needed ASCII • Several codes were considered but • ASCII won! American Standard Code for Information Interchange • The beginnings of the Internet in the 70’s also gave impetus to the desire for a standard code so that email clients didn’t have to know a dozen different codes just to read email from different machines across the Net ASCII • So what? Why do I care? Most of the time, you don’t. • If you press A on the keyboard and get an A on the screen, what does the code matter? • • • • ASCII is efficient, known by almost every device, easy to transmit and receive Has codes for A-Z, a-z, 0-9, space, punctuation marks and a few control codes 256 different codes (1 ASCII character fits into 1 byte of data) Textbook shows ASCII as seven bit code, later was made 8-bits. Time passes again • The world starts using computers and not just countries who use the “Roman” alphabet (Asian countries, Eastern European, Middle East) • First response from computer makers: sorry, learn English, use ASCII • But eventually the realization came that a new code that was bigger to represent more symbols was needed • Around 2000 Unicode was released • “Universal Code” • Has over 64K different codes Unicode • Covers all human alphabets and has room for more! • Includes ASCII as first 256 codes • A Unicode character takes TWICE as much space (at least!) as an ASCII character (2 bytes) • Now in development for 4 bytes! • Becoming the default code for many applications Unicode • Note: Unicode is NOT a “translator program” • What it does do is allow you (if you know a foreign language) to write the foreign words properly spelled with the correct characters • They will get transmitted correctly • The recipient still has to know how to read them, but at least the words will be correctly spelled • https://unicode-table.com/en/#control-character Interesting chart identifying the various languages Binary numbers • • • • A decimal number is “base 10”, it uses 10 different symbols (0,1,2, 3, 4, 5, 6, 7, 8,9) A binary number is “base 2”, it uses only 2 different symbols (0, 1) Computers do arithmetic with binary numbers, not decimals. Why? It’s easier to build a switch with TWO different states than one with TEN different states • http://www.cs.uky.edu/~keen/intro/b-to-d.html some tutorials for Binary to Decimal and Decimal to Binary conversion Computing and careers • Jobs in Computing • Research • Software Development • Systems Analysis • Jobs in other domains which use computers • • • • • Bioinformatics Engineering Medicine Manufacturing Finance Computers and careers • Demand for computer skills is projected to increase • Software Developer positions increase 17% from 2014 to 2024 • Web Developer positions increase 27% from 2014 to 2024 • Computer Systems Analyst positions increase 21% from 2014 to 2024 • Source www.bls.gov (Bureau of Labor Statistics) • Many low-level jobs are being replaced by automation