Harvard CS50x Online – Computer Science for Beginners
1 view 0 purchase
Course
CS50x
Institution
Harvard University
Unlock the world of computer science with the CS50x course! This online course, created by Harvard University, offers an in-depth introduction to the fundamentals of computer science and programming, making it ideal for beginners and those looking to solidify their problem-solving skills. Through e...
Lecture 0
!"Welcome
!"What is computer science?
!"Representing numbers
!"Text
!"Images, video, sounds
!"Algorithms
!"Pseudocode
!"Scratch basics
!"Abstraction
!"Conditionals and more
!"Demos
Welcome
, " This year, we’re back in Sanders Theatre, and David took CS50 himself as a sophomore
years ago, but only because the professor at the time allowed him to take the course
pass/fail.
" It turns out that computer science was less about programming than about problem
solving. And though there may be frustration from feeling stuck or making mistakes, there
will also be a great sense of gratification and pride from getting something to work or
completing some task.
" In fact, David lost two points on his first assignment for not following all of the
instructions correctly:
" And while this code (written in a programming language as opposed to a language
like English) looks cryptic at first, it may only take weeks or months before we can
understand main programming concepts and even teach ourselves new languages.
" Importantly,
what ultimately matters in this course is not so much where you end up relative to
your classmates but where you end up relative to yourself when you began
" In fact, two-thirds of CS50 students have never taken a computer science course before.
What is computer science?
" Computer science is fundamentally problem solving, but we’ll need to be precise and
methodical.
" We can think of problem solving as the process of taking some input (a problem we want
to solve) and generate some output (the solution to our problem).
, " To begin doing that, we’ll need a way to represent inputs and outputs, so we can store
and work with information in a standardized way.
Representing numbers
" To count the number of people in a room, we might start by using our fingers, one at a
time. This system is called unary, where each digit represents a single value of one.
" To count to higher numbers, we might use ten digits, 0 through 9, with a system called
decimal.
" Computers use a simpler system called binary, with just two digits, 0 and 1.
" For example, in binary this would be 0:
0 0 0
" And this would be 1:
0 0 1
" (We don’t need the leading zeroes, but we’ll include them to see the patterns more
easily.)
" Since there is no digit for 2, we’ll need to change another digit to represent the next
number:
0 1 0
" Then we’ll “add 1” to represent 3:
0 1 1
" And continue the pattern for 4 …:
1 0 0
, " … 5 …:
1 0 1
" … 6 …:
1 1 0
" … and 7:
1 1 1
" Each binary digit is also called a bit.
" Since computers run on electricity, which can be turned on or off, we can simply represent
a bit by turning some switch on or off to represent a 0 or 1.
" Inside modern computers, there are billions of tiny switches called transistors that can be
turned on and off to represent different values.
" And the pattern to count in binary with multiple bits is the same as the pattern in decimal
with multiple digits.
" For example, we know the following number in decimal represents one hundred and
twenty-three.
1 2 3
" The 3 is in the ones place, the 2 is in the tens place, and the 1 is in the hundreds
place.
" So 123 is 100×1 + 10×2 + 1×3 = 100 + 20 + 3 = 123 .
" Each place for a digit represents a power of ten, since there are ten possible digits
for each place. The rightmost place is for 100, the middle one 101, and the leftmost
place 102:
102 101 100
1 2 3
" In binary, with just two digits, we have powers of two for each place value:
22 21 20
# # #
" This is equivalent to:
4 2 1
# # #
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller arsalalivakalia09. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $10.49. You're not tied to anything after your purchase.
