5 Data (a) Describe one effect of using lossy compression to reduce the size of a file - Edexcel - GCSE Computer Science - Question 5 - 2023 - Paper 1

An image cannot be accurately represented using one bit per pixel because one bit can only represent two colors (typically black and white). This is insufficient for most images that contain various shades and colors, which require more bits to accurately depict all the details.

The reason the results of an arithmetic shift right and a logical shift right will differ is that a logical shift fills the empty bits with zeros, while an arithmetic shift maintains the sign bit (the leftmost bit) and fills the empty bits based on its value. This characteristic changes how negative numbers are treated in binary representation.

The binary pattern 0100 0010 converts to denary as follows:

$ext{2}^6 + ext{2}^1 = 64 + 2 = 66$

Thus, the denary equivalent is 66.

The binary pattern 0101 1011 converts to hexadecimal by grouping the bits into groups of four:

• 0101 = 5
• 1011 = B

Therefore, the hexadecimal equivalent is 5B.

With 6 bits, the number of unique values that can be represented is:

$2^6 = 64$

Therefore, there are 64 unique values.

To find the total number of bytes required to store the file, we can use the following expression:

$ext{Total storage} = ( ext{Number of rows} imes ext{Number of columns} imes ext{bits per integer}) + ext{kibibytes}$

In this case, it becomes:

$ext{Total storage} = (100 imes 600 imes 32/8) + 1 ext{ KiB}$

This gives the total bytes needed.

To draw the graph, label the x-axis as 'Time (s)' and the y-axis as 'Amplitude'. For values on the x-axis, plot from 0 to 1 second, marking intervals of 0.1 seconds. For the amplitude, represent each sample as an X at the corresponding height. Finally, connect the samples to show the digital form.