Higher Computing
Computer Systems
Homework 2
Higher Computing – Computer Systems (2)
1. There are two main ways that negative numbers can be represented in
a computer system. Name both of them.
Signed bit and Two’s Complement
2. What are the 3 steps in converting a positive whole number into Two’s
Complement.
Write down the +ve version of the number, flip the bits, add 1
3. What is the name of the process used to represent real numbers?
Floating point representation
4. What is a mantissa? Give an example.
The ‘number’ = .1101011
5. What is an exponent? Give an example.
The ‘power’ = x21101
6. How can you increase the precision of the number being stored?
Increase the number of bits available for the mantissa
7. What range of numbers can be represented in floating point if 4 bytes
is available for the mantissa and 1 byte for the exponent (ignore two’s
complement).
0 to 4 294 967 295 (232)
or .1111 1111 1111 1111 1111 1111 1111 1111 x 21111 1111
8. What is a:
a. Character
a letter number of nonprintable keystroke
b. Character set all the characters that can be represented on a
standard keyboard
c. Control character ASCII code 0-32 – nonprintable characters
9. What does ASCII stand for?
American Standard Code for Information Interchange
10. How many characters can true ASCII represent?
128
11. Give a reason for your answer to 10.
True ASCII only uses 7 bits
12. What is Unicode?
Another method of representing text in a computer
13. State one advantage of Unicode over ASCII?
More languages/characters can be represented
14. What is the name given to ASCII where it uses 8 bits?
Extended ASCII
Higher Computing
Computer Systems
Homework 2
15. In ASCII what range of numbers (decimal will do) represent all the
control characters?
0 - 32
16. Any information displayed on a computer screen is made up of tiny
dots. What are these called (Full name please)?
Picture Elements
17. What does each of these tiny dots represent in a computer?
1 bit
18. In a black and white bit-mapped graphic describe how any image is
constructed referring to ‘bits’ in your answer.
Bits represented as black are coded as 1’s and bits represented as
white are coded 0’s
19. Describe ‘Bit-Depth’
The number of bits used to represent a colour
20. Why is it necessary to compress files particularly graphic files?
To save storage space/make file transfer faster
21. What is the name given to the type of graphic where objects are
drawn on the screen?
Vector
22. What Bit-depth is needed to represent ‘True Colour’?
24
23. Name a lossless compressed graphic file type.
Gif
24. An A4 page (10x8) is to be scanned at 300dpi in 65,536 colours. What
is the storage requirement of the resulting file? Express your answer
in Megabytes showing all working.
No. of pixels per square inch= 300x300
No of square inches= 10x8
No of pixels= 10x8x300x300 = 7200000 pixels.
Total memory= 7200000x16 = 115200000 bits
115200000/8= 14400000 Bytes
14400000/1024= 14062.5 Kilobytes
14062.5/1024= 13.73 Megabytes