Computer Science GCSE notes

Data Representation

Define the term binary.
A language that a computer can understand is made up of “0” and “1”
ON and OFF, 0 turns off, 1 turns on, and a computer uses switches and electricity to
turn it on
The binary is base 2 because there are only 2 numbers
English is too complex for the computer so it converts it to binary

Denary is in base 10 because it has 10 numbers, 0-9, which gives you 10 digits

2 types of translators:
Compiler
Interpreter

-​ The interpreter executes one after the other
-​ The compiler will scan the code if there are no errors and execute them
simultaneously.

Advantages of the compiler:
-​ less time-consuming and more time efficient
The disadvantage of the compiler:
-​ https://docs.google.com/document/d/1AaZT6e1yhdGVk1xFCtxjAQk_62vi6VPNV-
Qr_O6_G8I/editit's less accurate.

Advantages of the interpreter:
-​ more accurate
Disadvantages of the interpreter:
-​ takes its less time efficient

5th September

-​ Binary goes from the highest weight to the lowest weight
-​ Denary has its values on the right, the maximum number you represent is 9

8-bit binary digits - multiply by 2, because it base 2 since it's only got 2 numbers

,VISUAL METHOD:
-​ Write out your 8-bit binary numbers
1,2,,4,8,16,32,64,128
-​ What is the biggest number that is closest to the number you are trying to
represent
-​ Turn on the digit you are going to use
-​ Subtract to find the number the remaining numbers that you need to represent
-​ Repeat step 3+4

BASE 2 METHOD

-​ If it is a whole number from the division, no decimal, then it is going to be “0”
-​ If its a decimal you round it up to “1”

QUESTIONS:



no. 128 64 32 16 8 4 2 1

56 0 0 1 1 1 0 0 0

67 0 1 0 0 0 0 1 1

121 0 1 1 1 1 0 0 1

220 1 1 0 1 1 1 0 0

223 1 1 0 1 1 1 1 1

1.​ 128+32+8+4+1 = 173
2.​ 128+64+32+16+4 = 244
3.​ 128+32+16+8+4+2+1 = 191
4.​ 128+8+4+2 = 142
5.​ 128+32+16+8+2+1 = 187

Analogue data = a continuous stream of data that is processed by humans.

Hexadecimal is a 16-base, so it includes 0-9 and then the letters A-F

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
A B C D E F

,What is half a bit:
4 bits is referred as a nibble
And 8 bits is referred as a byte




Converting from deanery to hexadecimal:

-​ Convert to its binary form
-​ Split the 8-bit binary into half
-​ Convert that into its hexadecimal form using its hexadecimal system

QUESTIONS:



128 64 32 16 8 4 2 1

57 0 0 1 1 1 0 0 1

8 4 2 1 8 4 2 1

3 9



128 64 32 16 8 4 2 1

111 0 1 1 0 1 1 1 1

8 4 2 1 8 4 2 1

6 F



128 64 32 16 8 4 2 1

139 1 0 0 0 1 0 1 1

8 4 2 1 8 4 2 1

8 B

, 128 64 32 16 8 4 2 1

250 1 1 1 1 1 0 1 0

8 4 2 1 8 4 2 1

F A



128 64 32 16 8 4 2 1

222 1 1 0 1 1 1 1 0

8 4 2 1 8 4 2 1

D E



128 64 32 16 8 4 2 1

1A 0 0 0 1 1 0 1 0

8 4 2 1 8 4 2 1

ANS: 1 10
26



128 64 32 16 8 4 2 1

FC 1 1 1 1 1 1 0 0

8 4 2 1 8 4 2 1

ANS:
252