N5 Computing - Computer Systems Revision

Computer Systems Revision

National 5 Computing Science

Binary Numbers

To be able to convert denary numbers to binary or vice versa, use the table below.

128

64

32

16

8

4

2

1

Floating point representation

​Used to store real numbers in binary using a mantissa and an exponent

ASCII

Text is represented in computer systems using ASCII. Each character is assigned a unique binary code.

Multiple Choice

How many bits does extended ASCII use to represent
a single character?

• 5

• 6

• 7

• 8

Vector graphics

Vector graphics store the attributes of objects in a drawing.

Multiple Choice

Which shape is not one that is identified in vector graphics?

• Square

• Ellipse

• Line

• Polygon

Multiple Choice

Which of the following is not an attribute of an ellipse?

• fill colour

• line colour

• coordinates

• line thickness

Bitmapped graphics

Bitmapped graphics store the binary colour code of every pixel in an image

Resolution measures the number
of pixels in an image

Inside the processor

The processor is at the centre of every computer system, repeatedly fetching and executing instructions

There are three main parts of the processor

● Control unit
● Registers
● ALU

Multiple Choice

Which part of the processor manages the fetching and execution of all instructions?

• ALU

• Register

• Control Unit

Multiple Choice

Which part of the processor makes all decisions and calculations?

• ALU

• Registers

• Control Unit

Multiple Choice

Which part of the processor stores data and instructions temporarily?

• ALU

• Registers

• Control Unit

Memory

Main memory holds all the running
programs and open files on your
computer

Memory is organised into many, many locations

Each location has a unique address so the data or instructions in one location can be fetched

Multiple Choice

What is not true about RAM?

• It stores data permanently

• It holds running programs

• It holds open files
  

• It is organised into lots of separate memory locations
  

• It can be read from or written to
  

Buses

CPU and RAM are connected by buses to
allow the CPU to fetch

The address bus finds a location in memory in order to read from it or write to it

The data bus transfers instructions and data between memory and processor

Translator programs

When you code in Visual Basic or Python, you use English-like commands such as Repeat, If, Integer, End etc.

The processor does not understand these commands - it only understands binary instructions

So any program has to be translated before it can be run

Translator programs

An interpreter translates and
executes one instruction at a time

It doesn’t save the translated code so has to be translated every time you want to run the program

It identifies errors as soon as the line is translated so is useful for debugging code and removing
mistakes

A compiler translates and executes the entire program in one operation

It saves the translated code so it
doesn’t have to be translated every time you want to run the program

Errors are only identified once all
the code is translated so compilers are best for producing a final version of software for release to customers

Multiple Select

Which are advantages of an interpreter?

• The user does not need a translator program to run the machine code therefore the program runs quicker and takes up less memory and processor time.

• Program will stop running when it encounters an error so it is easy to spot errors during the translation.

• The machine code is saved so the program only needs to be translated once.

Multiple Select

Which are advantages of compilers?

• The user does not need a translator program to run the machine code therefore the program runs quicker and takes up less memory and processor time.

• Less intensive on computer resources as don't need the translator and programming environment in future.

• 
  Never need to translate it again.

Environmental Impact

There are environmental implications of manufacturing and using computer devices.
These can be reduced by
recycling devices
switching off when not in use
using power down settings
using eco mode
reducing screen brghtness

Multiple Select

Which of the following are ways to reduce environmental impact of computers?

• Using solar or wind power to charge batteries
  

• Recycling old computer systems
  

• Dimming screen, going to standby or shutting down when not in use
  

• Uninstalling apps, turning off WiFi, GPS and Bluetooth

Security Risks

To reduce security risks, we use

Firewalls to filter incoming and outgoing data.
Encryption to encode data whilst being sent so that if intercepted it is unreadable and therefore worthless

Multiple Choice

What is a firewall?

• A network device that filters and checks all incoming and outgoing network traffic
  

• A network device that encrypts all data being sent so that, if intercepted, it cannot be read
  

• A network device that uses 2-factor authentication to verify your identity
  
  

• A network device that finds IP addresses based on URLs

Dropdown

​

Select answer

is a way to conceal information by altering it so that it appears to be random ​

Select answer

. Encryption is essential for ​

Select answer

on the Internet.