Data | Edexcel GCSE Computer Science (1CP2)

Data

128 questions
8 subtopics
Paper 1
Paper 1

Data is examined in Paper 1, Principles of Computer Science.

It covers binary, states and unsigned integers, two's complement, binary addition, overflow and shifts, hexadecimal, ASCII and the limits of binary representation, bitmap images, sound sampling and storage units, file sizes and compression.

Sample questions from Data

Answer each one closed book first, then open the answer.

Binary, states and unsigned integers

What is the smallest number of bits needed to give a unique code to each of 50 students?

Show the answer
Six bits are needed, since 2⁶ = 64 codes is enough for 50 students. Five bits give only 32 codes, which is too few.
Two's complement

Convert −45 to 8-bit two's complement.

Show the answer
The value −45 is 11010011 in 8-bit two's complement. Positive 45 is 00101101, its inverse is 11010010, and adding 1 gives 11010011.
Binary addition, overflow and shifts

How can you spot that overflow has happened when adding two 8-bit unsigned numbers?

Show the answer
Overflow has happened if a carry comes out of the most significant bit. The true answer would need a ninth bit.
Hexadecimal

Why is hexadecimal a better shorthand for binary than denary?

Show the answer
Each hex digit lines up with exactly four bits, so conversion is quick and exact. Denary digits do not match any fixed group of bits.
ASCII and the limits of binary representation

How do the ASCII codes for upper-case and lower-case letters differ?

Show the answer
Each lower-case letter's code is 32 more than its upper-case partner. The code for a is 97, while the code for A is 65.
Bitmap images

What colour depth does an image need to show 256 colours?

Show the answer
A 256-colour image needs a colour depth of 8 bits. Eight bits give 2⁸ = 256 patterns.
Sound sampling

What is the sample interval for a sample rate of 1,000 Hz?

Show the answer
The sample interval is 1 millisecond. The interval is 1 ÷ 1,000 = 0.001 seconds.
Storage units, file sizes and compression

Why is storage measured in binary multiples?

Show the answer
Memory and storage are addressed in binary, so capacities come in powers of 2. A binary multiple such as 1,024 = 2¹⁰ fits that structure exactly.

The 8 subtopics

One subtopic is one session. Work down the list.

Subtopic	What it covers	Questions
Binary, states and unsigned integers	Why computers use binary, the number of states n bits can represent, unsigned integers from 0 to 255, place values, and worked conversions between denary and binary.	16
Two's complement	Two's complement representation, the range −128 to +127, recognising negative values, worked conversions in both directions, and why the CPU uses it.	16
Binary addition, overflow and shifts	Rules for binary addition, worked 8-bit additions, overflow and its problems, logical left and right shifts, and arithmetic right shifts on negative numbers.	16
Hexadecimal	Hexadecimal digits and why programmers use them, why one digit stands for four bits, worked conversions between binary and hexadecimal, and web colours.	16
ASCII and the limits of binary representation	Character sets and 7-bit ASCII, working out codes from A = 65, upper and lower case, the limits of ASCII and Unicode, and the trade-off of using more bits.	16
Bitmap images	Pixels, resolution and colour depth, how many colours a given depth allows, the bitmap file size expression, and worked calculations in bytes and KiB.	16
Sound sampling	How analogue sound is sampled, amplitude, sample rate, sample interval and bit depth, their effect on quality and size, and worked sound file calculations.	16
Storage units, file sizes and compression	Bits, nibbles and bytes, kibibytes, mebibytes, gibibytes and tebibytes with worked conversions, and lossless and lossy compression including run-length encoding.	16

Data is 128 of the 680 questions in the guide.Get the guide, £7

How the guide is worked

Answering a question from memory stores it far better than reading the answer again. The guide runs that as a fixed procedure on one subtopic at a time, about twenty minutes a session.

Step 1 · Closed book
Cover the answers. Work through one subtopic and write down what you can. Leave blanks where you have nothing.
Step 2 · Open book
Go back to the top. Read each printed answer and write it out in full, including the ones you had right.
Step 3 · Closed book again
Same questions, same order, from memory. The gap between pass one and pass three is the session result.

Read the full method, the return schedule and the research behind it.