Class notes
CompSci Computer Systems (Year 11/GCSE/Nat 5)
- Course
- Institution
Complete class notes of computer science computer systems course with in depth explainations, diagrams, and exam tips.
[Show more]
Seller
Follow
zoeyim
Content preview
COMPSCIComputer Systems
Data Representation
Binary-term to describe data stored and processedby digital systems like computers, transmitted as a series of on
and off electrical pulses.
Why?
- Simplicity - messages sent by simplifying turing transistor on and off to allow electricity to pass
- Storage - data can be stored easily as it only needs on and offs
- Signal degradation - binary is resistance to electrical drops in voltage due to resistance as the value will not
change
1 bit = 1 binary digit (1)
1 byte = 8 binary digits (10011011)
Denary 128 64 32 16 8 4 2 1
=55
Binary 0 0 1 1 0 1 1 1
Floating Point Representation -a way to store realnumbers in a form of scientific notation
0. 164 × 1
0
2
10100100 10
The mantissa - digits that make up the number - 164
Mantissa Exponent
The base - number that it is multiplied by - 10
he digits that
T he number of places to
T
The exponent - the power that defines how many times to multiply by - 2
make up the move the digits
Can also be written in base 2 (binary) number
10
0. 10100100 × 2
The binary point will always be left of number, and base is always 2 thus negating the need to store the “x2”
ASCII- American Standard Code for Information Interchange.
Computers use binary numbers to store characters that make up text, punctuation, and symbols. The oldest
standard system is ASCII. It uses 7 bits of binary to define 128 characters. Extended ASCII covers 8 bits which
allows more symbols.
First 32 characters (0-31) are non-printable characters and are used to control peripherals or send signals to devices.
(e.g. Backspace, Cancel, New line)
“Hi” -> 72 105 -> 01000110 01100111
Current standard is called UNICODE that uses 16 bits (650000) characters to represent symbols.
79
, Vector Graphics -a series of instructions describingshapes and lines to produce images. Not for real-world scenes
as they are too complex to break down into a list of objects and attributes. Used commonly for icon design,
simplistic drawings, or flowcharts and graphs.
Objects:
- Rectangles
- Ellipses
- Polygons
- Lines
Attributes:
- Coordinates
- Line colour
- Fill colour
SVG (Scalable Vector Graphics) are how vector graphics are produced on webpages.
Rectangle :<rectx="50"y="20"width="100"height="80"
style
="
fill
:
b
lue
;
s
troke-width
:
3
;
s
troke
:
red
"
/>
Rectis the name of the object, a rectangle
x=”50” y=”20”
are the coordinates of the top leftcorner. These are given from left and top margin of SVG area
in pixels
width=”100” height=”80”define width and height ofrectangle
Attributes containing fill colour and line colour are in thestyleproperty.
Ellipse:<ellipsecx="250"cy="170"rx="100"ry="50"
style
="
fill
:
r
ed
;
s
troke
:
purple
;
stroke-width
:
5
"
/>
rx=”100” ry=”50”they define the radius from centrepoint along the x and y axis (if same value, make circle)
cx=”250” cy=”170”are coordinates of the centre ofthe ellipse
Line:<linex1="200"y1="20"x2="450"y2="160"style="stroke:black"/>
x1=”200 y1=”20”gives the start of the line coordinates
x2=”450” y2=”160”gives the end of the line coordinates
Polygon:<polygonpoints="250,250 450,450 50,450"
style
="
fill
:
y
ellow
;
stroke
:
black
;
stroke-width
:
10
"
/>
points=”250,250 450,450 50,450”defines the coordinatesof the corners of the shape in x,y pairs. Three pairs
create a triangle
80
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 zoeyim. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $5.50. You're not tied to anything after your purchase.
Can Stuvia be trusted?
4.6 stars on Google & Trustpilot (+1000 reviews)
78600 documents were sold in the last 30 days
Founded in 2010, the go-to place to buy study notes for 14 years now