J277/01, Computer Systems, June 2023

Q1 (a)

Computers represent data in binary form

Tick (✓) one box to identify the statement about binary that is true.

 

• Binary digits can only be the values 0, 1 and 2

• The left-most bit of a binary integer has the smallest value

• The left-most bit of a binary integer has the smallest value

• Binary is used because computers are made of switches that can only be on or off

Q1 (b) i

What is the value in Denary of the 8-bit number 00000111 ?

It's value in Hexadecimal is 7.

Q1 (b) ii

What is the value in 8-bit binary of Denary 49?

It's value in Hexadecimal is 31.

Q1 (b) iii

What is the Denary value of the 8-bit binary 01100110. It's value in Hexadecimal is 66.

Q1 (b) iv

What is the Hexadecimal value of the 8-bit binary 11110100?

It's value in denary is 244.

Q1 (d)

Tick (✓) one box to identify the largest file size.

 

• 2 000 000 bytes

• 2300 KB

• 200 MB

• 0.1 GB

Q1 (e)

Complete the binary addition by adding these two 8-bit binary numbers.

Answer explanation

Some responses converted each binary number to denary, added these, and then converted them back to binary. This allowed them to access the final answer mark, but not the mark for showing their working. The mark for showing working out required candidates to show how the data was carried.

Q1 (f)

Identify the binary shift that has been applied to the 8-bit binary number 10110000 to get the result 10000000.

A ​ (a)   ​ (b)   place ​ (c)  

• left
• 3
• shift
• right
• 2
• rotate
• up
• 4

Answer explanation

This question was often answered well. For full marks, candidates needed to accurately identify that it was a left 3-place shift. Some responses only gave the direction, i.e. left, and did not note the number of marks (2) that can identify the level of response required

Q 2(a) i

A student is performing a range of actions on the internet using their computer.
A range of protocols are used for the transmission of data by the student’s computer, and the web servers they are accessing.

• HTTP / HTTPS

• Requesting to view a news webpage from a web server

• IMAP / POP

• Downloading a large text document from a web server

• HTTPS

• Downloading a text document from a web server

• FTP

• Requesting to view a news webpage from a web server

Q 2(a) ii

      ii.        Some protocols have layers.

Give two reasons why protocols have layers.

• Separates tasks so they can be developed independently

• One layer can be changed without affecting the others

• A developer can focus on all layers

• Groups tasks so they can be developed together

Answer explanation

Candidates were often able to show an understanding of layers but could not say why layers are used. The most common responses referred to the need for independence between layers, and that it provides the ability to change one layer without having to change/impact on any other layers.