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FOUNDATIONS OF
COMPUTER SCIENCE
From Data Manipulation to Theory of
Computation
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Book
organization
Computersand Data
ComputerHardware
ComputerSoftware
DataOrganization
AdvancedTopics
Chapter 1: Introduction
Chapter 2: Data Representation
Chapter 3: NumberRepresentationChapter 4: Operations on Bits
Chapter 5: ComputerOrganizationChapter 6: Computer Network
Chapter 7: Operating Systems
Chapter 8: Algorithms
Chapter 9: ProgrammingLanguagesChapter 10: Software Engineering
Chapter 11: Data Structures
Chapter 12: Abstract Data Types
Chapter 13: File Structures
Chapter 14: DatabasesChapter 15: Data compression
Chapter 16: Security
Chapter 17: Theory ofComputation
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Introduction
Chapter 1
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1.1 THE COMPUTER AS A BLACK BOX
DATA PROCESSORYou can think of a computer as a data processor. Usingthis definition, a computer acts as a black box that accepts
input data, processes the data, and creates output data.
Although this model can define the functionality of a
computer today, it is too general.It is not clear how many types or sets of operations a
machine based on this model can perform.
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PROGRAMMABLE DATA PROCESSOR
This model adds one extra element to the computer: theprogram. A program is a set of instructions written in acomputer language that tells the computer what to do withdata.
In the new model, the output data depend on thecombination of two factors: the input data and the program.
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Same program, different input data
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Same input
data,
differentprograms
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1.2 VON NEUMANN MODEL
Every computer today is based on the von Neumann model.
It is based on three ideas.FOUR SUBSYSTEMS
The model defines a computer as four subsystems: memory,
arithmetic logic unit, control unit, and input/output.
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Memory
Memory is the storage area. It is where programs and data
are stored during processing.
Arithmetic Logic Unit (ALU)
The ALU is where calculation and logical operations take
place.
Control UnitThe control unit controls the operations of the memory,
ALU, and the input/output subsystem.
Input/Output
The input subsystem accepts input data and the programfrom outside the computer; the output subsystem sends
the result of processing to the outside.
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STORED PROGRAM CONCEPT
The von Neumann model states that the program must be
stored in memory. This is totally different from thearchitecture of early computers in which only the data were
stored in memory.
Both the data and programs should have the same format
because they are stored in memory. They are, in fact,stored as binary patterns (a sequence of 0s and 1s ) in
memory.
SEQUENTIAL EXECUTION OF INSTRUCTIONS
A program in the von Neumann model is made of a finitenumber of instructions. In this model, the control unit
fetches one instruction from memory, interprets it, and then
executes it.
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1.5 COMPUTER SOFTWARE
PROGRAMS MUST BE STORED
A SQUENCE OF INSTRUCTIONS
Another requirement of the model is that the program must
be a sequence of instructions. Each instruction operates on
one or more data items.
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ALGORITHMS
The step-by-step solution is called an algorithm.
LANGUAGESA computer language has a more limited number of symbolsand also a limited of words .
SOFTWARE ENGINEERING
Software engineering is the design and writing of structuredprograms. Today, it is not acceptable just to write a program
that does a task; the program must follow strict principles and
rules.
OPERATING SYSTEMSAn operating system originally worked as a manager to
facilitate access of the computer components for a program.
Today, operating systems do much more.
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1.6 HISTORY
MECHANICAL MACHINES (BEFORE 1930)
BIRTH OF ELECTRONIC COMPUTERS (1930-1950) Early Electronic Computers
The early computers of this period did not store theprogram in memory; all were programmed externally.
The first general-purpose, totally electronic computer wasmade by John Mauchly and J.Presper Eckert and wascalled ENIAC (Electronic Numerical Integrator andCalculator). It was completed in 1946.
Computers Based on the von Neumann ModelThe first computer based on von Neumanns idea wasmade in 1950 at the University of Pennsylvania and wascalled EDVAC (Electronic Discrete Variable AutomaticComputer).
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COMPUTER GENERATIONS (1950-PRESENT)
Computer built after 1950 are following, more or less, thevon Neumann model. The computers has become faster,
smaller, and cheaper, but the principle is almost the same.
Each generation witnesses some major change in
hardware or software (but not the model).
The first generation is characterized by the emergence of
commercial computers. Computers were bulky and used
vacuum tubes as electric switches.
First Generation (roughly 1950-1959)
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The invention of integrated circuit (transistors, wiring, and
other components on a single chip) reduced the cost and
size of computers even further. Minicomputers appeared
on the market. Software industry was born.
Third Generation (roughly 1965 -1975 )
Second-generation computers used transistorsinstead of
vacuum tubes. This reduced the size of computers as well astheir cost. Two high-level programming languages,
FORTRAN and COBOL , were invented and made
programming easier.
Second Generation (roughly 1959-1965)
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The fourth generation saw the appearance of
microcomputers. Advances in the electronics industryallowed whole computer subsystems to fit on a single
circuit board. This generation also saw the emergence of
computer networks.
Fourth Generation (approximately 1975-1985)
The fifth generation witnessed the appearance of laptop
and palmtop computers, improvements in secondary
storage media (CD-ROM, DVD, etc.), the use of
multimedia, and the phenomenon of virtual reality.
Fifth Generation (approximately 1985-NOW)
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