NUMBER SYSTEM
A numeral system is a writing system for
expressing numbers; that is, a mathematical notation for representing numbers
of a given set, using digits or other symbols in a consistent manner. The same
sequence of symbols may represent different numbers in different numeral
systems.
Two types of number systems are:
- Non-positional number systems
- Positional number systems
1. NON-POSITIONAL NUMBER SYSTEMS
Characteristics
- Use symbols such as i for 1, ii for 2, iii
for 3, iiii for 4, iiiii for 5, etc.
- Each symbol represents the same value regardless of its position in the number.
- The symbols are simply added to find out the value of a particular number.
Difficulty
- It is difficult to perform arithmetic with such a number system.
2. POSITIONAL NUMBER SYSTEMS
- The value of each digit is determined by:
- The digit itself
- The position of the digit in the number
- The base of the number system
(base = total number of digits
in the number system)
- The maximum value of a single digit is always equal to one less than the value of the base
Characteristics
- Use only a few symbols called digits.
- These symbols represent different values depending on the position they occupy in the number.
DECIMAL NUMBER SYSTEM
Characteristics
- A positional number system has 10 symbols
or digits (0, 1, 2, 3, 4, 5, 6, 7, 8, 9). Hence, its base = 10.
- The maximum value of a single digit is 9
(one less than the value of the base).
- Each position of a digit represents a specific power of the base (10)
- We use this number system in our day-to-day life.
Example
258610 = (2 x 103) + (5 x 102) + (8 x 101) + (6 x 100)
= 2000 + 500 + 80 + 6
BINARY NUMBER SYSTEM
Characteristics
- A positional number system has only 2 symbols or digits (0 and 1). Hence its base = 2.
- The maximum value of a single digit is 1 (one less than the value of the base).
- Each position of a digit represents a specific power of the base (2).
- This number system is used in computers.
Example
101012 = (1 x 24) + (0 x 23) + (1 x 22) + (0 x 21) x (1 x 20)
= 16 + 0 + 4 + 0 + 1
= 2110
Representing numbers in different number systems
In order to be specific about which number
system we are referring to, it is a common practice to indicate the base as a
subscript. Thus, we write:
101012 = 2110
BIT (Binary digiT)
- Bit stands for binary digit.
- A bit in computer terminology means either a 0 or a 1.
- A binary number consisting of n bits is called an n-bit number.
Characteristics
- A positional number system has total 8 symbols or digits (0, 1, 2, 3, 4, 5, 6, 7). Hence, its base = 8.
- The maximum value of a single digit is 7 (one less than the value of the base.
- Each position of a digit represents a
specific power of The base (8).
OCTAL NUMBER SYSTEMS
Since there are only 8 digits, 3 bits (23 = 8) are sufficient to represent any octal number in binary
Example
20578
= (2 x 83) + (0 x 82) + (5 x 81) + (7 x 80)
= 1024 + 0 + 40 + 7
= 107110
HEXADECIMAL NUMBER SYSTEM
Characteristics
- A positional number system has total 16 symbols or digits (0, 1, 2, 3, 4, 5, 6, 7, 8, 9, a, b, c, d, e, f). Hence its base = 16.
- The symbols a, b, c, d, e and f represent the decimal values 10, 11, 12, 13, 14 and 15 respectively.
- The maximum value of a single digit is 15 (one less than the value of the base).
- Each position of a digit represents a specific power of the base (16).
- Since there are only 16 digits, 4 bits (24 = 16) are sufficient to represent any hexadecimal number in binary.
Example
1af16 = (1 x 162) + (a x 161) + (f x 160)
= 1 x 256 + 10 x 16 + 15 x 1
= 256 + 160 + 15
= 43110
CONVERT A NUMBER'S BASE:
Another base number to decimal base
Method
Step 1: determine the column (positional)
value of each digit
Step 2: multiply the obtained column values
by the digits in the corresponding columns
Step 3: calculate the sum of these products
Example
47068 = ?10
Common values multiplied by the corresponding
digits
47068 = 4 x 83 + 7 x 82 + 0 x 81 + 6 x 80
= 4 x 512 + 7 x 64 + 0 + 6 x 1
= 2048 + 448 + 0 + 6
Sum of these products
= 250210
Base
Decimal base to another base
Division-remainder method
- Step 1: divide the decimal number to be converted by the value of the new base
- Step 2: record the remainder from step 1 as the right most digit (least significant digit) of the new base number.
- Step 3: divide the quotient of the previous divide by the new bas
- Step 4: record the remainder from step 3 as the next digit (to the left) of the new base number
Repeat steps 3 and 4, recording remainders
from right to left, until the quotient becomes zero in step 3 note that the
last remainder thus obtained will be the most significant digit (msd) of the
new base number
Example
95210 = ?8
Solution:
8 |
952 |
Reminders |
|
119 |
0 |
|
14 |
7 |
|
1 |
6 |
|
0 |
1 |
Hence, 95210 = 16708
Some based to another based
- Step 1: convert the original number to a decimal number (base 10)
- Step 2: convert the decimal number so obtained to the new base number
Example
5456 = ?4
Solution:
Step 1: convert from base 6 to base 10
5456 = 5 x 62 +
4 x 61 + 5 x 60
= 5 x 36 + 4 x 6 + 5 x 1
= 180 + 24 + 5
= 20910
Step 2: convert 20910 to base 4
4 |
209 |
Reminders |
|
52 |
1 |
|
13 |
0 |
|
3 |
1 |
|
0 |
3 |
Hence, 20910 =
31014
So, 5456 =
20910 = 31014
Thus, 5456 = 31014
Shortcut method for converting:
Binary number to its equivalent octal number
- Step 1: divide the digits into groups of three starting from the right.
- Step 2: convert each group of three binary digits to one octal digit using the method of binary to decimal conversion.
Example
11010102 = ?8
Step 1: divide the binary digits into
groups of 3 starting from right
001 101 010
Step 2: convert each group into one octal
digit
0012 = 0 x 22 + 0 x 21 + 1 x 20 = 1
1012 = 1 x 22 + 0 x 21 + 1 x 20 = 5
0102 = 0 x 22 + 1 x 21 + 0 x 20 = 2
Hence, 11010102 = 1528
Octal number to its equivalent binary number
- Step 1: convert each octal digit to a 3 digit binary number (the octal digits may be treated as decimal for this conversion).
- Step 2: combine all the resulting binary groups (of 3 digits each) into a single binary number.
Example
5628 = ?2
Step 1: convert each octal digit to 3
binary digits
58 = 1012, 68 = 1102, 28 = 0102
Step 2: combine the binary groups
5628 = 101/5 110/6 010/2
Hence, 5628 = 1011100102
Binary number to hexadecimal number
- Step 1: divide the binary digits into groups of four starting from the right
- Step 2: combine each group of four binary digits to one hexadecimal digit
Example
1111012 = ?16
Step 1: divide the binary digits into groups
of four starting from the right
0011 1101
Step 2: convert each group into a
hexadecimal digit
00112 = 0 x 23 + 0 x 22 + 1 x 21 + 1 x 20 = 310 = 316
11012 = 1 x 23 + 1 x 22 + 0 x 21 + 1 x 20 = 310 = d16
Hence, 1111012 = 3d16
Hexadecimal to its equivalent binary number
- Step 1: convert the decimal equivalent of each hexadecimal digit to a 4 digit binary number.
- Step 2: combine all the resulting binary groups (of 4 digits each) in a single binary number.
Example
2ab16 = ?2
- Step 1: convert each hexadecimal digit to a 4 digit binary number
216 = 210 = 00102
A16 = 1010 = 10102
B16 = 1110 = 10112
- Step 2: combine the binary groups
2ab16 = 0010/2 1010/a 1011/b
Hence, 2ab16 = 0010101010112ractional numbers
10. FRACTIONAL NUMBERS
Fractional numbers are formed same way as decimal number
system
In general, a number in a number system with base b Would be written as:
An an-1… a0 . A-1 a-2 … a-m
And would be interpreted to mean:
An x bn + an-1 x bn-1 + … + a0 x b0 + a-1 x b-1 + a-2 x b-2 + … + a-m x b-m
The symbols an, an-1, …, a-m in above representation should be one of the b symbols
allowed in the number system
Formation of fractional & binary number system
Binary point
Position 4 3 2 1 0 . -1 -2 -3 -4
Position value
24 23 22 21 20 2-1 2-2 2-3 2-4
Quantity represented
16 8 4 2 1 ½ 1/4 1/8 1/16
Example
110.1012 = 1 x 22 + 1 x 21 + 0 x 20 + 1 x 2-1 + 0 x 2-2 + 1 x 2-3
= 4 + 2 + 0 + 0.5 + 0 + 0.125
= 6.62510
Number system (example)
Octal point
Position 3 2 1 0 . -1 -2 -3
Position value
83 82 81 80 . 8-1 8-2 8-3
Quantity represented
512 64 8 1 1/8 1/64 1/512
Example
127.548
= 1 x 82 + 2 x 81 + 7 x 80 + 5 x 8-1 + 4 x 8-2
= 64 + 16 + 7 + 5/8 + 4/64
= 87 + 0.625 + 0.0625
= 87.687510
Key words/phrases
- Base
- Least significant digit (lsd)
- Binary number system
- Memory dump
- Binary point
- Most significant digit (msd)
- Bit
- Non-positional number
- Decimal number system
- System
- Division-remainder technique
- Number system
- Fractional numbers
- Octal number system
- Hexadecimal number system
- Positional number system
Questions from this unit: