# Paper 1 Revision

Create an expression

In the exam you may be asked to 'create an expression' to show something. This simply means to show the sum. So if you are told a program to calculate the size of a rectangle height 500 width 400 the expression would simply be....

500 X 400

Colour Depth

24-bits are used to represent the colour in the file. All colours are combinations of RGB. Each of R, G, B is 8bits / 8bits areallocated to the three primary colours, red, green, blue. 3 colours x 8bits each = 24 bits. 24-bits are used to represent the colour of each pixel.

One of the colours used in an image is ‘cadet blue’.‘Cadet blue’ in binary is 0101 1111 1001 1110 1010 0000. Convert 0101 1111 1001 1110 1010 0000 to hexadecimal.

Hexadecimal numbers are 0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,15. A-F replace the values 10 to 15.

Convert each 4 digit binary number (nibble) to decimal.

 8 4 2 1 0 1 0 1

So to calculate the first number (4x1)+(1x1)=5.

5F9EA0

Practice converting binary into hex and vice versa.

1100 0011 0010 1110

1010 0101 1111 0111

1101 1010 1100 0011

1F 9E DD C1

6B B6 A1 7C

9A B8 7C 3D

Next......

Convert the denary number 60 to 8-bit binary.

 128 64 32 16 8 4 2 1

Convert the 8-bit binary number 0010 0011 to denary.

Show the result of..

0010 0011 + 0100 1010

0011 0110 + 0110 0010

0110 0110 + 0100 1011

0011 0010 + 0110 1110

Truth Tables

A player earns a badge for every 100 questions they answer correctly, providing this includes at least 10 hard questions or 30 medium questions. This can be expressed as (NQ >= 100) and (HQ >= 10 or MQ >= 30).Complete the truth table.

Embedded Systems

Embedded system control car headlights by: A sensor could be used (with a microprocessor) to determine light levels to activatea switch/ turn on/off the headlights.

Explain how an embedded system could control windscreen wipers.

Explain how an embedded system could control the lights in a classroom.

Bits

A bit can have two different states.State how many bits are needed to represent the 26 capital letters A to Z.Give a reason for your answer.

5-bits are needed. Because 4-bits only represents 16 values and because 5-bits represent up to 32 values.

How many bits are needed to represent ascii values (128)?

Time = number of bits / bits per second:       81×1024×1024×8

54×1000×1000

What if the network speed was 78?

What if the audiobook file was 128MB?

Encryption

Make sure you know what encryption is and why it is used.

Complete the table using a Caesar Cipher algorithm.

Explain one special condition a Caesar Cipher algorithm must handle.

Networks

Find out 3 reasons for connecting devices to networks.

Find out 3 reasons why an organisation should use wireless connectivity for their network.

A network specialist might perform 'penetration testing' research this term and add it to your notes.

A network specialist might also carry out a code review. Find out what this would involve and again add to your notes.

Compilers and interpreters translate source code written in programming languages. State four other features of a compiler.

Routers have an important role in how the internet functions.Describe how a router directs data on the internet.

Compression

A lossy compression algorithm reduces the size of a file by removing data. Explain why data loss is acceptable when using lossy compression.

A run-length encoding (RLE) algorithm reduces the size of a file based on runs of repeated items. For example, wwwbbbwwbbbbbbwwww would be reduced to 3w3b2w6b4w. Explain why RLE may NOT be a good choice for encoding a text file.

Storage

Research 3 features of each of the following storage types....

Cloud

Solid State

Magnetic

Optical

(ROM or RAM?)____________ stores BIOS / bootstrap / start-up.

(ROM or RAM?)____________ stores currently executingprograms and data.

Virtualisation uses layers of abstraction to hide the details of hardware devices and processes from the end user. ‘Cloud storage can be viewed as a virtualisation.’ Research this statement and add the details to your notes.

Hardware & Software

John von Neumann proposed the concept of a stored program. State the two items he proposed to store in main memory.

Find out what each of these CPU parts do....

• Bus
• Control Unit
• Arithmetic Logic Unit
• Register

Q: Describe how the operating system uses scheduling to allocate processor time.

A: All processes are held in a queue, Processes are prioritised, Processes are switched on each clock cycle.

Now: Create a diagram to illustrate this process and add it to your revision notes.

• Find out what utility software does and add this to your notes.
• Find out what the term unpatched software means and add it to your notes.
• Find out what read only access means.