What is a Computer?

Introduction to Computers
Processes data into
Accepts data information
Raw facts, figures, and
Company
Data that is organized,
symbols
meaningful, and useful
Logo

@
Produces and stores results

„ Components: Hardware + Software

„ Generally, the term is used to describe a collection of
Digital Computer Concept and Practice devices that function together as a system.

What is a Computer? Computer System (Hardware)

Input devices + Processor (CPU) + Output devices
„ A machine for automatically performing calculations
„ A computer is an electronic device, operating under Monitor
(output)
Speaker
(output) System unit
the control of instructions (software) stored in its (processor, memory…)
own memory unit, that can accept data (input), Printer
(output)
manipulate data (process), and produce information
(output) from the processing.

Storage devices
(CD-ROM, Hard disk,
USB memory,…)
Mouse
(input)
Scanner Keyboard
(input) (input)
 Software
„ How does a computer know what to do?
„ It must be given a detailed list of instructions

(computer program or software) that tells it

exactly what to do.
Categories of Computers
User

Application Software

System Software

Hardware

Software 컴퓨터의 종류
„ System software „ Data type
„ Programs that control or maintain the operations „ Digital computers (vs. analog computers)
of a computer and its devices „ Purpose
„ Operating systems
„ General (vs. domain-specific)
„ MS Windows, Mac OS X, Unix
„ Size (processing capacity)
„ Personal computer (PC)
„ Application software „ Mainframe
„ Program that perform specific tasks for users
„ Supercomputer
„ Word processing software, graphics software,

moving picture players

 Personal Computer (PC) Mainframe
„ Mainly used by large organizations
„ Computer systems developed for individuals
„ Focusing on business problems and reliable
„ Price, size, and capabilities
operations
„ Census, industry or consumer statistics, and financial
transaction processing.

Personal Computer (PC) Supercomputer

„ Employed for specialized applications that requires
„ Laptop
massive amounts of mathematical calculations
„ PDA (Personal Digital Assistant)
„ Weather forecasting, nuclear energy research, etc.
Mainframe vs. Supercomputers The Early Period: Up to 1940

„ Mainframe „ 1672: The Pascaline

„ Execute many programs concurrently „ Designed and built by Blaise Pascal

„ Business purpose „ One of the first mechanical calculators

„ Supercomputer „ Could do addition and subtraction

„ Execute a few programs as fast as possible

„ Scientific purpose

The Early Period: Up to 1940

„ 1674: Leibnitz’s Wheel
„ Constructed by Gottfried Leibnitz

„ Mechanical calculator

History of Computer Hardware „ Could do addition, subtraction, multiplication,

and division
 The Early Period: Up to 1940 The Early Period: Up to 1940

„ 1801: The Jacquard loom „ 1823: The Difference Engine

„ Developed by Joseph Jacquard „ Developed by Charles Babbage

„ Automated loom „ Did addition, subtraction, multiplication, and

„ Used punched cards to division to 6 significant digits

create desired pattern „ Solved polynomial equations and other complex

mathematical problems

Punched Cards Difference Engine

http://acarol.woz.org

Jacquard Loom

CTR Census Machine

 The Early Period: Up to 1940 The Early Period: Up to 1940
„ 1890: U.S. census carried out with programmable
„ 1830s: The Analytic Engine card processing machines
„ Designed by Charles Babbage
„ Built by Herman Hollerith
„ Mechanical general-purpose computer
„ These machines could automatically read, tally,
„ Components were functionally similar to the four and sort data entered on punched cards
major components of today’s computers „ 1880 census: 8 years Æ 1890 census: 1 year
„ Mill Æ arithmetic/logic unit

„ Store Æ memory

„ Operator Æ processor
Tabulating Machine Company (1896)
„ Output Æ input/output Æ Computing Tabulating Recording
Corporation (1911)
Æ IBM (1924)

Analytic Engine The Birth of Computers: 1940-1950

„ First computer programmer: Ada Byron „ Development of electronic, general-purpose

„ The modern computer programming language, computers
“Ada” is named in her honor. „ Did not begin until after 1940

„ Was fueled in large part by needs of World War II

„ Early digital computers

„ Mark I

„ ENIAC (Electronic Numerical Integrator and Calculator)

„ ABC (Atanasoff-Berry Computer)

„ Colossus

„ Z1
 ENIAC The Modern Era: 1950 to the Present

„ 1st generation of computing (1950-1959)

„ Used vacuum tubes to store data and programs

„ Each computer was multiple rooms in size

„ Computers were not very reliable

„ ABC, ENIAC, EDSAC, EDVAC, UNIVAC

The Birth of Computers: 1940-1950 The Modern Era: 1950 to the Present
„ 2nd generation of computing (1959-1965)
„ Stored program computer model „ Vacuum tubes Æ transistors and magnetic cores
„ Proposed by John Von Neumann in 1946
„ Dramatic reduction in size

„ Stored binary algorithm in the computer’s „ Computer could fit into a single room
memory along with the data „ Increase in reliability of computers

„ Is known as the Von Neumann architecture „ Reduced costs of computers

„ Modern computers remain, fundamentally, Von „ High-level programming languages (FORTRAN,

Neumann machines COBOL)

„ First stored program computers „ The programmer occupation was born

„ EDVAC

„ EDSAC
The Modern Era: 1950 to the Present The Modern Era: 1950 to the Present

„ 3rd generation of computing (1965-1975)

„ Used integrated circuits (ICs) rather than

individual electronic components

„ Further reduction in size and cost of computers

„ Computers became desk-sized

„ First minicomputer developed

„ Software industry formed

The Altair 8800: world’s first microcomputer

The Modern Era: 1950 to the Present Future?

„ 4th generation of computing (1975-current) „ Quantum computer

„ Reduced to the size of a typewriter
„ DNA computing
„ Appearance of
„ Chemical computer
„ Computer networks
„ Optical computer
„ Electronic mail

„ Graphical user interfaces (GUIs)

„ Apple Computer (Steve Jobs and Steve Wozniak, 1977)

„ IBM PC (1981)

„ Microsoft: MS-DOS
 Turing Machine

„ Abstract symbol-manipulating device

„ A thought experiment about the limits of mechanical
computation (Not a practical computing technology)
Theoretical Models of Computers

head

tape

Church’s Thesis Turing Machine

„ Every 'function which would naturally be regarded as „ A tape which is divided into cells, one next to the
computable' can be computed by a Turing machine. other. Each cell contains a symbol from some finite
alphabet.
„ Any computer with a certain minimum capability is,
in principle, capable of performing the same tasks „ A head that can read and write symbols on the tape
and move left and right one step at a time.
that any other computer can perform.
„ A state register that stores the state of the Turing
machine.
„ An action table (or transition function) that tells the
machine what symbol to write, how to move the
head and what its new state will be, given the symbol
it has just read on the tape and the state it is currently
in.
 Von Neumann Architecture

„ Modern computer Î “Programmable”

„ Stored program architecture
„ Nearly all modern computers implement some form
of the stored program architecture
„ Computers are controlled by stored programs
(algorithms).

- Contributions of John von Neumann (1903-1957)

quantum physics, functional analysis, set theory,
economics and game theory, computer science,
numerical analysis, hydrodynamics (of
explosions), statistics, …

CPU

(1) Fetch an instruction from memory

(2) Fetch any data required by the instruction from
memory
(3) Execute the instruction
(4) Store results in memory
(5) Go back to Step (1)