Computer Science G9 Important Points

How are analogue sound waves converted to digital?

1) record audio with set sample rate, bit depth
2) measure the amplitude and frequency of the audio
3) The ADR converts this information into binary values

Sampling

Taking measurements of a sound wave at regular but different intervals of time

Fidelity

Relationship between original sound and recording

What affects fidelity?

1) Sample rate
2) bit depth (bits used to store each sample)

Advantages of digital recording over analogue?

Cheap to record
Easily copied, edited, shared (portable)
Do not physically deteriorate

Formula for calculating image file size

length x width x color depth

Formula for calculating sound file size

sample rate x bit depth x duration of recording x no of channels

Bandwidth

The amount of data that can be carried on a network in a given period of time

Lossy compression

Compressing a file where some of the data is removed, and the original file cannot be recovered

Loseless compression

Compressing a file such that it can decompressed without any loss of data

How is lossy compression performed on images?

The computer makes tiny differences in colors to the same colors to rewrite it using fewer bits (less color depth).

How is lossy compression performed on audio?

The computer removes wavelengths of audio we cannot hear and small different in volume and frequency that we cannot distinguish.

Algorithm

a process or set of rules to be followed in calculations or other problem-solving operations, especially by a computer.

Syntax errors

Typos and other small mistakes in code

Logical errors

The programmer uses the wrong strategy resulting to incorrect results

Runtime error

An error that occurs whilst the program is running

Presence check

Check if a value is between two values

Present check

Check if a value is present or not

Length check

Check if a text is too short or long

Pattern check

Whether an input matches certain criteria

Lookup check

Whether the input is one of the predefined values in an array of values