COS151 Chapter 1 Summary

COS 151 Study Notes

Covers Chapter 1



1.1 Turing Model ........................................................................................................................ 1
1.1.1 Data Processors ............................................................................................................ 1
1.1.2 Programmable Data Processors ................................................................................... 1
1.1.3 The Universal Turing Machine ...................................................................................... 1
1.2 Von Neumann Model ............................................................................................................ 2
1.2.1 Four Subsystems........................................................................................................... 2
1.2.2 The Stored Program Concept ....................................................................................... 2
1.2.3 Sequential Execution of Instructions ............................................................................ 2
1.3 Computer Components......................................................................................................... 3
1.3.1 Computer Hardware ..................................................................................................... 3
1.3.2 Data .............................................................................................................................. 3
1.3.3 Computer Software ...................................................................................................... 3
1.4 History .................................................................................................................................. 5
1.4.1 Mechanical machines (before 1930) ............................................................................ 5
1.4.2 The Birth of Electronic Computers (1930-1950) ........................................................... 5
1.4.3 Computer Generations (1950-Present) ........................................................................ 6
1.5 Computer Science as a Discipline .......................................................................................... 8




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, 1.1 Turing Model

• The idea of a universal computational device was first proposed by Alan Turing in 1936
• A Turing machine can perform all types of computations
• Alan Turing abstracted the actions of people into a model for a computational machine.
• The Turing model has changed the world



1.1.1 Data Processors
• A computer can be defined as a data processor
• A computer acts as a black box that accepts data, processes data, and then creates output
data
• The problem with the Blackbox model is that it is too general and fails to specify the processing
type, or if more than one type of processing is possible.
• Computers are general-purpose machines according to present day definitions; thus, a single-
purpose computing machine cannot be termed as a computer.



1.1.2 Programmable Data Processors
• The Turing model is a better model for a general-purpose computer — this model adds an
extra element (the program) to a computing machine.
• A program is a set of instructions that tells the computer what to do with the data.
• The output data depends on the input data and the program for Turing model machines —
we can generate different outputs with the same program if we change the input data.
• If the input data and program remain the same, the output data should be consistent.


1.1.3 The Universal Turing Machine
• This is a machine that performs any computation if an appropriate program is provided.
• It can be proved that a very powerful computer and a universal Turing machine can compute
the same thing.
• A universal Turing computer can compute anything computable.




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