AS Level · Topics 1–2
Represent information and transmit it
Connect number representations, multimedia size, compression, and network delivery.
Lessons distinguish AS topics 1–12 from A Level topics 13–20. Examples include Cambridge pseudocode and Python.
Interpret the bit pattern
An eight-bit unsigned value ranges from 0 to 255. With two's complement, the most significant bit has weight -128, so the same eight bits can represent -128 to 127. Always state the representation before converting a pattern.
For an uncompressed bitmap, multiply width, height, and bits per pixel. For sampled sound, multiply sample rate, duration, resolution, and channels. Convert bits to bytes and use the units requested by the question before rounding.
Explain a transmission choice
Lossless compression keeps every detail needed to reconstruct the original; lossy compression trades information for smaller files. Choose based on the data: changing a bit in a program is different from losing a small visual detail in a photograph.
A network's addressing, routing, transmission medium, and protocols solve different problems. Explain which characteristic addresses the scenario's need. A fast local link does not remove congestion elsewhere in an internet path.
Check yourself
What does 11111001 represent as an eight-bit two's-complement integer?Show answer
-7. Its unsigned value is 249, and 249 - 256 = -7.
References used to build these lessons
We used these official documents as references when building this course's lessons. They are the sources for the syllabus structure and course requirements.
Cambridge International · 9618 · Exams 2027–2029