N5 Computer Systems

N5 Computing Science

Computer Systems

By Miss Lyon

Computer Systems

• Data Representation ​

• Computer Structure

• ​Security Precautions

• ​Environmental Impact

Using 8-bit extended ASCII to represent text in a computer system.

Text

Converting binary numbers to denary and vice versa

Describing ​floating point representation

Numbers

Data Representation

Binary to Denary

Each bit in a binary number has a place value. The right-most bit always has the value - 1. Each bit after is found by doubling the value on the right.

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Take your 8 bit binary number and place under each of the column headings. Add up the values with a 1 in that column.

Multiple Choice

What denary number is being represented in binary? 0000  1010 

• 6
• 8
• 10
• 12

Multiple Choice

What is 1111 1111 in denary?

• 225

• 244

• 255

• 222

Denary to Binary

Begin with the same column headings (place values)

Then determine if the denary number greater than or equal to the place value

​Yes:

• enter a 1 below the place value

• subtract the place value from the denary number - this is the remainder

No:​

• enter a 0 below the place value

Repeat these steps working from left to right until the remainder equals 0​

Multiple Choice

How is the number 5 represented in binary?

• 00000001
• 00000011
• 00000101
• 00001001

Multiple Choice

How is the number 128 represented in binary?

• 1000 0000

• 0000 0001

• 1111 1111

• 1100 0000

Floating Point Representation​

Real numbers are numbers with a decimal point.

To store a real number the computer moves the decimal point to the left hand side.

The number is then stored in 2 parts, the mantissa and the exponent.

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​

Multiple Choice

0.100101 x 2⁵

What is the mantissa?

• 100101

• 2

• 5

Multiple Choice

0.100101 x 2⁵

What is the exponent?

• 100101

• 2

• 5

Extended ASCII (8 bit)

Extended ASCII uses 8 bits to represent each character and can represent 256 characters.

​

• ​Some characters are printable (A, b, !, 2)

• Some characters are control (​ctrl, backspace, escape)

• You can calculate the storage requirement of a word by assigning 8 bits to every character​

  E.g. DOG 3 characters x 8 bits = 24 bits

Multiple Choice

This is a printable character

• shift

• alt

• delete

• A

Multiple Choice

How many bits are used per character in extended ASCII?

• 6

• 8

• 7

• 4

Multiple Choice

How many bits are required to store the word HELLO ?

• 5 bits

• 40 bits

• 8 bits

• 48 bits

Describe common vector objects and attributes

Graphics - Vector

Describe how bitmapped method of graphics representation

Graphics - Bitmap

Data Representation

Bitmapped Graphics

• A bit-mapped graphic is stored as a 2D array of pixels

• The resolution of a bit-mapped graphic is its total number of pixels

• The colour of each pixel is stored as a binary value

​

• The bit depth of the image is the number of bits used to store each colour - as bit-depth increases, file size increases

​

​

Vector Graphics

​Objects:

• rectangle

• ellipse

• line

• polygon

​

​

​Attributes:

• co-ordinates

• fill colour

• line colour

​​

Vector graphics represent images using shape objects.

Each object has attributes which describe how it is to be drawn.

​

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Multiple Choice

An image made up of pixels

• Bitmapped
• Vector

Multiple Choice

Line colour, fill colour, x/y coordinates are vector...

• attributes

• objects

• things

• items

Multiple Choice

An advantage of using a bitmap graphic

• can be edited at pixel level

• they can be pixelated

Multiple Choice

What vector object is this an example of?

• circle

• ellipse

• line

• rectangle

Describe the purpose of computer buses:

• data bus

• address bus​

Buses

Describe the purpose of processor components:

• ALU

• Control Unit

• ​Registers

Processor

Computer Structure

Processor Components

Manages the flow of data around the computer, sends control signals to other parts of the system

Control Unit

Arithmetic and Logic Unit - carries out any calculations, comparisons and logic

ALU

Registers

Fast temporary storage locations on the processor,

​stores data being used by the CPU

Multiple Choice

Which of the following is not part of the processor?

• ALU

• Control Unit

• Registers

• RAM

Multiple Choice

Which part of the processor stores data?

• ALU

• Registers

• Control Unit

• RAM

Multiple Choice

Which part of the processor carries out comparisons

• Control Unit

• Arithmetic and Logic Unit

• Registers

• RAM

Multiple Choice

Which part of the processor sends out control signals?

• Control Unit

• Arithmetic and Logic Unit

• Registers

• RAM

Multiple Choice

Which part of the processor is responsible for carrying out mathematical calculations

• ALU

• Control Unit

• CPU

• Registers

Buses and Memory

Each memory location has its own unique address which is used by the address bus to read/write data to the correct place.

Memory Locations

• Carries data to and from memory to the processor

• ​is bi-directional because data can travel in both directions

Data Bus

Address Bus

• Tells memory which memory location is being read from and written to

• only goes in one direction

Multiple Choice

What bus is used to carry data to and from the processor from memory?

• Data Bus

• Control Bus

• First Bus

• Address Bus

Multiple Choice

This is used to carry the unique memory location of data from the processor to memory

• Address Bus

• Control Bus

• Data Bus

• First Bus

Translators

Translators (interpreters and compilers) translate high level language code to binary (machine code)

Compiler: translates in one go.

Advantages:

• Program only needs to be compiled once

• The compiler does not need to remain in memory once compiled, as the object code can run independently

Disadvantage:

• Harder to debug because all of the errors are reported once the program has been compiled

Interpreter: translates one line at a time.

Advantage:

• Errors are flagged after each line has been interpreted making debugging easier

Disadvantages:

• Slower - statements in a loop are translated repeatedly

• Interpreter must remain in memory to allow the program to run

Multiple Choice

What is this description of " this translates the whole program only after every line has been written"

• Compiler

• interpreter

• translator

• HLL

Multiple Choice

Translators are used to convert High Level Language code to Machine Code

• True

• False

Multiple Choice

Machine code is another name for...

• binary

• High Level Language

• Python

• Java

Multiple Choice

Which of the following is NOT an example of a high level language

• binary

• Python

• Java

• Visual Basic

Encryption is the process of scrambling data so that it is unreadable by any unauthorised person.

​A key is requried to decrypt the data

Encryption​

A firewall protects a network against unauthorised access by monitoring network traffic and deciding what gets through

Firewalls

Security Precautions

Multiple Choice

What is the name of the security precaution that makes data unreadable to anyone without the key?

• firewall

• encryption

• anti-virus

• encipher

Environmental Impact

Energy Use​

Energy use of computer systems can be reduced through:

• ​monitor settings

• ​power down settings

• ​computers on stand-by

Multiple Choice

Which of the following would not be a method of saving energy

• using a screensaver

• turning down the brightness on the monitor

• activate stand by mode

• use power saving settings on the hard drive