Introduction: Riddle of Computer Science
Writing Motivation
Einstein: If you can’t explain a problem to a six-year-old child, you don’t really understand it
Writing Goal
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if(you have read this book):
while(end of world and computers no longer exist):
you can build computers from scratch, cool!Chapter One: First Introduction to Computing
The Essence of Computing
- Counting with fingers is the simplest computer
- Computation graph: Abstraction is a crucial method in computer science
- Parallel computing
Parallel computing is good, but it also introduces other problems:
- Parallel computing computers have different computation speeds: waiting time is too long!
- Communication overhead between computers greatly reduces efficiency
- Compilation
(5 - 3) * (4 + (2 * 3 - 5) * 6)
===>
{
a = 2 * 3
b = a - 5
c = b * 6
d = 4 + c
e = 5 - 3
e * d
}
Making the result of statements completely consistent with the original expression. This translation process that preserves the original semantics is called compilation
- Functions Consider the following scenario: We want to express a “fan controller”, where the fan speed is always twice the current temperature.
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t->t*2 //This is our fan controller, which is also the simplest function:
f(t) = t*2 //Let's be more formal
f(2) // value is 4
Branching Consider the following scenario: We want a “beverage selector”
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t-> if(t < 22)
{
"hotpot"
}
else
{
"ice cream"
}
Summary: Elements of computation
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Basic values. (integers, strings, boolean values, etc.)
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Expressions. (basic arithmetic expressions)
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Variables and assignment statements.
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Branch statements
Functions and function calls
Like learning to drive a car, once you master the gas pedal, brakes, gear shifter, steering wheel, and speedometer functions and usage, you’ve learned to drive all cars, regardless of their model.
