SET 2 Flashcards
Explain signed bit and it’s problems
The most significant bit is set to 1 for negative and 0 for positive
-problems: two values for 0, discontinuity in numbers
Give two advantages of using two compliment
- One value for 0
- continuity of numbers
How to store decimal numbers
Using floating point with the mantisa and exponent
In floating point notation what determine the accuracy of the number
Number of bits allocated to the mantissa
Describe how BMS images are stored
- As a grid of pixels each pixel has a binary representation in memory
- Whole screen stored
- number of bits for each pixel determines the range of colours available
Describe how vector images are stored
As objects and their attributes
E.g rectangle (start X,Y, length,breadth, line, fill)
The advantages of Vector over BM graphics
- Can layer objects
- Can scale up without loss of resolution
- Can edit individual attributes is easily
The advantages of BM over vector graphics
- Can edit at pixel level
- More realistic, for photographs
Add a circle to an image describe effect on file size of both BM and vector images
- Vector file size will increase as additional object stored
- BM no change to file size as stores whole screen with no layering
Give advantages and disadvantages of floating point notation
Advantage: can Store very large and very small numbers
Disadvantage: Accuracy may be reduced depending on the number of bits available
What determines the range of real numbers
Number of bits allocated to exponent
Explain bit depth
- Number of bits used to store each pixel
- determines the range of colours
If you increase the bit depth of a photo after it was taken, why is there no improvement
Picture will only have colours that were available need to do it before taking photo
Describe two effects of reducing the bit depth of an image
Reduces file size
reduces range of colours available
Explain resolution
Number of pixels making up an image measured in DPI
What do the first 32 to ASCII codes represent
Control characters ( non-printable) E.g escape
Why do computers use binary
- Only 4 arithmetic rules so Simple calculations
- Only two values so robust
What is a parity bit
- A parity bit or check bit is the simplest form of error detection
- A bit added to the end of binary code that indicates whether the number of 1s in the binary number is even or odd
Name five types of computers
Laptop tablet smartphone desktop mainframe
State three criteria to consider when buying a laptop
- RAM capacity ( 3 GB or more) -Processor speed ( 3 GHz or faster)
- Hard disc capacity ( 300 GB or more)
Give advantages of a touch screen as an input device
- Don’t need any extra hardware such as keyboard
- Touch screens work well with icon driven systems
- Little data to enter so easily and less chance of error
Give disadvantages of a touch screen as an input device
- Users must be able to accurately select targets on touchscreens, and avoid accidental selection of adjacent targets
- Not suitable for entering large amounts of data
- Not robust: can break easily if dropped
- More expensive than alternatives such as mouse or keyboard
Why is it important that hardware is scalable
If a company expands then they need to be able to cope with sudden increase in number of users
Name three software consideration
- Open source vs proprietary source
- licensing
- portability
