05) mathematics for general computing.pptx
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Mathematics for General Computing
Department of Mathematics &
Computer ScienceFaculty of Natural Sciences
The Open University of Sri Lanka
April 27, 2023 DMCS 1
What is a Number System? “A 'number system' is a set of numbers, (in
the broadest sense of the word), together with one or more operations, such as addition or multiplication” Wikipedia
Ex: Natural numbers, Integers, Rational Numbers, Complex numbers, Binary, Octal, Decimal, etc..
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Decimal Number SystemContain 10 digits
0, 1, 2, 3, 4, 5, 6, 7, 8, 9
Called as 10 base number system
April 27, 2023DMCS
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3 2 7
102 101 100
10 x Bigger
Binary Number SystemWe use the decimal system in everyday life
because it seems more natural (we have ten fingers and ten toes).
For the computer, the binary system is more natural because of its electrical nature (On versus Off).
Has only two digits1, 0
April 27, 2023DMCS
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Octal Number SystemContain 8 digits
0, 1, 2, 3, 4, 5, 6, 7Programs often display data in octal format
because it is relatively easy for humans to read
Easily be translated into binary formatBy contrast, decimal format is the easiest
format for humans to read, but translating between decimal and binary formats is relatively difficult. April 27, 2023
DMCS5
Hexadecimal Number SystemContain 16 digits
0, 1, 2, 3, 4, 5, 6, 7,8, 9, A, B, C, D, E, FEasier for humans to read hexadecimal
numbers than binary numbersHexadecimal numbers have either an 0x
prefix or an h suffix
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Conversion between Number systemDecimal to binaryDecimal to OctalDecimal to HexadecimalBinary to DecimalOctal to DecimalHexadecimal to DecimalOctal to BinaryHexadecimal to Binary
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Decimal to BinaryE.g.: convert decimal number 65 to binary
6510 = 1000001b
Sample footer 8
65232 - 1
216 - 0
2 8 - 0
2 4 - 0
2 2 - 0
2 1 - 0
Binary to Decimal 1 0 0 0 0 0 1
1 x 1 = 1 = 65
20
21
26
25
24
23
22 2
x 0= 0 +
4 x 0= 0 +
8 x 0 = 0 +
16x 0 =0 +
32x 0 = 0 +
64x 1 = 64 +
Decimal to OctalE.g.: convert decimal number 65 to octal
6510 = 101oct
Sample footer 10
658 8 - 18 1 - 0
Octal to Decimal 1 0 1
= 65
82
81
80 1x 1 =1 +
8x 0 = 0 +
64x 1 = 64 +
Decimal to HexadecimalE.g.: convert decimal number 65 to octal
6510 = 41hex
Sample footer 12
6516 4 - 1
Hexadecimal to Decimal 4 1
= 65
161
160 1x 1 =1
16x 4 = 64 +
Octal to Binary
3 4 5 6
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011
100
101
110
3456 oct = 011100101110b
Hexadecimal to Binary
3 F 7 A
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0011 1111 0100
1010
3F7Ahex = 0011111101001010b
Bits and BytesComputer can understand only On or Off
value as On – 1 Off -0Therefore binary number system is used in
computer system5V (ON)
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0V (OFF)
Cont…
The word bit is a shortening of the words "Binary digIT”
8 bits = 1 byte 10110011 10111000 11110011 we have 24 bits
that is equal to 3 bytes Eight-bit can represent 256 values (28 values, 0–
255)
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Cont… When you start talking about lots of bytes, you get
into prefixes like kilo, mega and giga, as in kilobyte, megabyte and gigabyte
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ASCII ASCII - American Standard Code for Information
Interchange American Standard Institute has introduced coding
system to number all characters and numbers by giving it a label between 0 and 255.
Ex: A – 65 , B – 66 To store a character we need to calculate binary
equivalent of ASCII number and send it to computer Ex: A -65 – 01000001
There are other number system as EBCDIC, Extended Binary Coded Decimal Interchange Code adopted by IBM
April 27, 2023 Sample footer 19
Cont… ASCII is fine for the most common English characters,
numbers and punctuation but is a bit limiting for the rest of the world
Therefore Unicode standards are using These days the Unicode standard defines values for
over 100,000 characters
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