Give two reasons why computers use binary numbers to represent and store data.(2)
- A two state system is easy to represent using electrical signals.
- Fewer rules need to be built into the processor for arithmetic operations.
- It is also easy to represent a two state system on storage devices, eg. CD-ROM
Represent 0111 0100 in decimal.(1)
- 0 + 64 + 32 + 16 + 0 + 4 + 0 + 0= 116
Describe how graphics are stored using a bit-mapped package.(2)
- A bit map is a grid of pixels.
- Each pixel has a binary value representing its colour.
- All pixels in the image are stored even if they have not been assigned a colour.
An image is 4 x 6 inches, has a resolution of 800 dpi and each pixel can display 65,536 different colours. Calculate the storage requirements of this image. Express your answer using suitable units. Show all working. (3)
- (4×800)x(6×800)x16
- =3200x4800x16 = 245760000 bits
- /8 = 30720000 bytes / 1024 =
- 30000 Kb / 1024 = 29.3 Mb
State two advantages of storing the above image as a vector graphic rather than a bit-map.(2)
- The image can be resized without pixelation
- The file size will be much smaller as only a description of how to draw the object is stored, not each pixel.
- Individual objects can be edited without affecting the rest of the image (non-destructive editing)
Represent 13.25 in floating point notation. Express the mantissa in 16-bits and the exponent in 8-bits.(2)
- 1101.01
- Mantissa = 1101 0100 0000 0000
- Exponent = 0000 0100
- 1101 0100 0000 0000 x 2 0000 0100
What is meant by the term lossless compression?(1)
- File size of graphic is reduced without any visible reduction in graphic quality
Explain how the Unicode system overcomes the limitations of ASCII.(1)
- Unicode uses 16-bits compared to ASCII’s 7-bit representation. This allows all the world’s character sets to be represented instead of just 128 characters.
How many different colours could be represented with a bit depth of one byte(1)
- 1 byte = 8 bits
- 28 = 256
- 256 different colours can be represented
