All of the letters, symbols and digits that a computer system can represent
Which term is the name of the standard seven-bit code developed in the 1960s to represent the English alphabet?
ASCII
What is meant by 7-bit ASCII?
A character set that stores each character as a seven-bit code and can represent 128 characters
What is the name for a single letter, digit or symbol that a computer can represent?
Character
What is the name for the unique seven-bit pattern that a computer stores to represent one particular character?
ASCII code
How many different characters can be represented using 7-bit ASCII?
128 characters
Capital A has the ASCII code 65. What is the ASCII code for capital E?
69
A standard keyboard needs codes for around 98 different characters. What is the minimum number of bits needed to give each one its own code?
7
What is a limitation of using 7-bit ASCII to represent characters?
Only 128 different characters can be represented, so some languages cannot be stored
A program inputs the character '7', which is stored using the ASCII code 55. What must the program do to use this value as a number in a calculation?
Convert the character to an integer
The 16-character string 'Computer Science' is stored using 7-bit ASCII. How many bytes are needed to store it?
14 bytes
The digit 0 has the ASCII code 48. What is the ASCII code for the digit 6?
54
Why does each character in a character set need its own unique code?
So that any stored code can be decoded back to a single character
A program stores the text AaA using 7-bit ASCII. How many different codes are stored?
Two, because the letters A and a are different characters
A text file contains the symbol # as well as letters and digits. Why can the symbol be stored in the file?
It is a character in the ASCII set with its own code
Which term describes the number of bits used to store the colour of each pixel in an image?
Colour depth
What is meant by a bitmap image?
An image made up of a grid of pixels, each stored as a binary value for its colour
What is meant by a monochrome image?
An image where each pixel is stored using a single bit
Which two factors determine the file size of a bitmap image?
The number of pixels and the number of bits per pixel
What is a pixel in a bitmap image?
The smallest identifiable area of an image
In a bitmap image, what does the binary value stored for each pixel represent?
The colour of that pixel
A bitmap image uses a colour depth of 4 bits per pixel. How many different colours can it represent?
16 colours
An image is 20 pixels wide and 30 pixels high and uses 8 bits per pixel. How many bits are needed to store it?
4800 bits
What does the resolution of a bitmap image describe?
The number of pixels in its width and height
A photograph is saved again at a higher resolution while keeping the same colour depth. What is the effect?
The image shows more detail and needs more storage
An image is saved using a lower colour depth but the same resolution. What is the effect?
Fewer colours are available and the file is smaller
A pixel is stored using 24-bit colour. How are these bits used?
8 bits each for red, green and blue
A photo of the sky is saved as a bitmap using only 2 bits per pixel. Why does it look worse than the original?
Only four colours can be stored, so the shades appear in bands
A monochrome image is stored using one bit per pixel, where 1 represents black and 0 represents white. One row of the image is stored as 0110. What does this row show?
One white pixel, two black pixels, one white pixel
A designer wants every pixel in an image to be able to show 256 different colours. How many bits are needed to store each pixel?
8 bits
A pixel is stored using 32 bits. Three groups of 8 bits store its red, green and blue values. What is the last group of 8 bits used for?
To store how transparent the pixel is
A photograph is saved again using a higher colour depth at the same resolution. Why does the quality of the image improve?
Each pixel can be given more possible colour values
Which statement correctly compares resolution and colour depth?
Resolution counts the pixels while colour depth counts the bits per pixel
Four images are described by their dimensions. Which image has the highest resolution?
1920 by 1080
A monochrome icon is 8 pixels wide and 8 pixels high. How many bits are needed to store it?
64 bits
Which term describes the number of measurements taken from an analogue sound wave each second?
Sample rate
What is meant by the bit depth of a digitised sound?
The number of bits used to record each measurement of the sound wave
What is meant by the amplitude of an analogue sound wave?
The height of the wave at the point at which it is measured
Which term describes the length of time between one measurement of a sound wave and the next?
Sample interval
What is meant by a sample in digitised sound?
A measurement of the amplitude of a sound wave at a given time
Which unit is used to measure the number of measurements taken from a sound wave each second?
Hertz
Which component converts an analogue sound signal into digital data so that a computer can store it?
An analogue to digital convertor
Which statement describes the difference between analogue and digital sound signals?
Analogue signals are continuous and digital signals are discrete
Which term means the same as bit depth?
Sample resolution
A sound file is described as having a sample rate of 44,100 Hz. What does this value tell you?
44,100 samples are taken every second
Why must an analogue sound wave be sampled before a computer can store it?
A computer can only store discrete binary values
A computer plays a stored music file through speakers. Which component converts the digital data back into an analogue signal?
A digital to analogue convertor
A recording is made again with a higher sample rate but the same bit depth and duration. What is the result?
More samples are taken so the sound file becomes larger
A sound is recorded for 3 seconds at a sample rate of 1,000 Hz and a bit depth of 8 bits. What is the file size in bits?
24,000 bits
A sound wave is sampled every 0.002 seconds. What is the sample rate of the recording in hertz?
500 Hz
A recording is made using a very low bit depth. Why does this reduce the quality of the sound file?
Each wave height is rounded to one of a few values
A sound is stored using a 3-bit bit depth. How many different values can be used to record the amplitude of each sample?
8
Why does recording with a low sample rate reduce the quality of the digitised sound?
The wave is measured less often so rapid changes are missed
A sound is recorded for 4 seconds at a sample rate of 500 Hz. How many samples are stored in the recording?
2,000
Two recordings of the same sound use the same sample rate and last the same time. Recording A has a bit depth of 16 bits and recording B has a bit depth of 8 bits. Which statement is true?
A is a larger file and records each wave height more accurately
Why is a digitised recording never an exact copy of the original analogue sound?
The wave is measured at intervals and each value is rounded