Home learning - Topics
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Networks
Ethical and Legal
Binary and Denary
Search and Sort Algorithms
SQL
LI: Revision for areas for development
Home learning – This week lesson 1
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Networks
Ethical and Legal
Binary and Denary (73-77)
Search and Sort Algorithms (43-48)
SQL
LI: Revision for areas for development
Binary / Denary Recap
• Computers can only process Binary Data. This means that only 0s and 1s can
be processed by a computer. (This is called a Base 2 system)
• We use a number system to count that uses :
0123456789
This is called a decimal or denary system (Base 10)
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Denary to Binary
• Remember when converting Denary (numbers we know – sometimes called
decimal) to Binary. Use the table below:
128
64
32
16
8
4
2
1
• If I was needing the number 80 representing in binary, you would start from
the left and add a 1 for all of the numbers you need to make that number.
128
64
32
16
8
4
2
1
0
1
0
1
0
0
0
0
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Denary to Binary
• When given a binary number to convert be careful. If the binary number is 4
digits, you will need the last 4 columns (bits). If I was given 1001, I would do
the following:
128
64
32
16
8
4
2
1
1
0
0
1
• You would then count the number where a 1 exists. There is a 1 under the 8
column so we add that to the total and we also add the 1.
8+1 = 9
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How to work out Hexadecimal from Denary (Method 1)
• If I started with a Denary number, in this case we will use 100. Convert it
to Binary
128
64
32
16
8
4
2
1
0
1
1
0
0
1
0
0
• Then we break the 8 bit number into two. This makes two nibbles of
4bits. The headings change for now too.
8
4
2
1
8
4
2
1
0
1
1
0
0
1
0
0
• Add the numbers and choose the Hex character from the table. The first
4 bit is 6, which stays the same. The second nibble is 4, so this stays as
this number. The hex number is therefore 64
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0=0
1=1
2=2
3=3
4=4
5=5
6=6
7=7
8=8
9=9
10=A
11=B
12=C
13=D
14=E
15=F
How to work out Hexadecimal from Denary (Method 2)
• If I started with a Denary number, in this case we will use 100.
• As Hexadecimal is Base16 (this means there are 16 possible options per
bit) we need to divide it by 16. The remainder is the second nibble.
• So…
100/16= 6 with a remainder 4.
As the numbers are lower than 10, we keep them as they are so the Hex
number is 64
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0=0
1=1
2=2
3=3
4=4
5=5
6=6
7=7
8=8
9=9
10=A
11=B
12=C
13=D
14=E
15=F
How to work out Denary from Hexadecimal
(Method 1 and 2)
• If we start with hexadecimal 64, we can change this back in two
ways
Method 1
64
Change it back to binary
8
4
2
1
8
4
2
1
0
1
1
0
0
1
0
0
Bring them back together and change the
headings back. Then add
128
64
32
16
8
4
2
1
0
1
1
0
0
1
0
0
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=100
Method 2
64
Take the first value and times it by
16 (if a letter convert it to its number from the
table)
The second digit needs to be
multiplied by 1
16 x 6 = 96
4x1=4
0=0
1=1
2=2
3=3
4=4
5=5
6=6
7=7
8=8
9=9
10=A
11=B
12=C
13=D
14=E
15=F
The exam paper
• Attempt Questions 1-4 on the exam paper
• I have also included an addition question to see how you go.
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Search Algorithms
There are two types of Algorithm to search for a value in a
list
Linear
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Binary
Linear Search
Jane has a list of numbers: 81, 42, 9, 76, 15
To find the number 76…you would need to check each
number and to write it you do the following:
81
76
42
76
9
76
76 = 76
STOP
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• Positives
• The list doesn’t have to
be in order.
• It will always find the
value
Negative
• May take a longer time
for larger lists
Binary Search
Jane has a list of numbers: 81, 42, 9, 76, 15
Put the numbers in order
9, 15, 42, 76, 81
• Then choose the median, which is 42. This is too low
so you would discard 42 and the numbers to the left.
• You would be left with 76, 81
• Choose the median, it would probably choose 81 and
it is not the correct value so it would choose the only
number lower as the answer.
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• Positives
• Much faster for larger
lists
Negative
• Needs to be in order
Sort Algorithms
There are three types of Algorithm to Sort the values in a list
Bubble
Bubble Sort Video
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Insertion
Merge
Insertion Sort Video
Merge Sort Video
The exam paper
• Attempt the remaining questions
• Don’t forget to answer and then check the markscheme at the end.
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