I haven't learned this in programming class before, but now I need to know it. What are some good resources for learning these numbers and how to convert them? I pretty much am going to memorise these like the times table.
In our everyday decimal system, the base number, or radix is 10
.
A number system's radix tells us how many different digits are in use.
In decimal system we use digits 0
through 9
.
The significance of a digit is radix ^ i
, where i
is digit's position counting from right, starting at zero.
Decimal number 6789
broken down:
6 7 8 9 radix ^ i
│ │ │ │ ──────────────
│ │ │ └── ones 10 ^ 0 = 1
│ │ └───── tens 10 ^ 1 = 10
│ └──────── hundreds 10 ^ 2 = 100
└─────────── thousands 10 ^ 3 = 1000
ones tens hundreds thousands
───────────────────────────────────────────────
(9 * 1) + (8 * 10) + (7 * 100) + (6 * 1000)
= 9 + 80 + 700 + 6000
= 6789
This scheme will help us understand any number system in terms of decimal numbers.
Hexadecimal system's radix is 16
, so we need to employ additional digits A...F
to denote 10...15
.
Let's break down hexadecimal number CDEFh
in a similar fashion:
C D E F radix ^ i
│ │ │ │ ──────────────
│ │ │ └── ones 16 ^ 0 = 1
│ │ └───── sixteens 16 ^ 1 = 16
│ └──────── 256:s 16 ^ 2 = 256
└─────────── 4096:s 16 ^ 3 = 4096
ones sixteens 256:s 4096:s
───────────────────────────────────────────────
(Fh * 1) + (Eh * 16) + (Dh * 256) + (Ch * 4096)
= (15 * 1) + (14 * 16) + (13 * 256) + (12 * 4096)
= 15 + 224 + 3328 + 49152
= 52719
We have just converted the number CDEFh
to decimal (i.e. switched base 16
to base 10
).
In binary system, the radix is 2
, so only digits 0
and 1
are used.
Here is the conversion of binary number 1010b
to decimal:
1 0 1 0 radix ^ i
│ │ │ │ ──────────────
│ │ │ └── ones 2 ^ 0 = 1
│ │ └───── twos 2 ^ 1 = 2
│ └──────── fours 2 ^ 2 = 4
└─────────── eights 2 ^ 3 = 8
ones twos fours eights
───────────────────────────────────────────────
(0 * 1) + (1 * 2) + (0 * 4) + (1 * 8)
= 0 + 2 + 0 + 8
= 10
Octal system - same thing, radix is 8
, digits 0...7
are in use.
Converting octal 04567
to decimal:
4 5 6 7 radix ^ i
│ │ │ │ ──────────────
│ │ │ └── ones 8 ^ 0 = 1
│ │ └───── eights 8 ^ 1 = 8
│ └──────── 64:s 8 ^ 2 = 64
└─────────── 512:s 8 ^ 3 = 512
ones eights 64:s 512:s
───────────────────────────────────────────────
(7 * 1) + (6 * 8) + (5 * 64) + (4 * 512)
= 7 + 48 + 320 + 2048
= 2423
So, to do a conversion between number systems is to simply change the radix.
To learn about bitwise operators, see http://www.eskimo.com/~scs/cclass/int/sx4ab.html.
1: http://en.wikipedia.org/wiki/RadixIn our everyday decimal system, the base number, or radix is 10
.
A number system's radix tells us how many different digits are in use.
In decimal system we use digits 0
through 9
.
The significance of a digit is radix ^ i
, where i
is digit's position counting from right, starting at zero.
Decimal number 6789
broken down:
6 7 8 9 radix ^ i
│ │ │ │ ──────────────
│ │ │ └── ones 10 ^ 0 = 1
│ │ └───── tens 10 ^ 1 = 10
│ └──────── hundreds 10 ^ 2 = 100
└─────────── thousands 10 ^ 3 = 1000
ones tens hundreds thousands
───────────────────────────────────────────────
(9 * 1) + (8 * 10) + (7 * 100) + (6 * 1000)
= 9 + 80 + 700 + 6000
= 6789
This scheme will help us understand any number system in terms of decimal numbers.
Hexadecimal system's radix is 16
, so we need to employ additional digits A...F
to denote 10...15
.
Let's break down hexadecimal number CDEFh
in a similar fashion:
C D E F radix ^ i
│ │ │ │ ──────────────
│ │ │ └── ones 16 ^ 0 = 1
│ │ └───── sixteens 16 ^ 1 = 16
│ └──────── 256:s 16 ^ 2 = 256
└─────────── 4096:s 16 ^ 3 = 4096
ones sixteens 256:s 4096:s
───────────────────────────────────────────────
(Fh * 1) + (Eh * 16) + (Dh * 256) + (Ch * 4096)
= (15 * 1) + (14 * 16) + (13 * 256) + (12 * 4096)
= 15 + 224 + 3328 + 49152
= 52719
We have just converted the number CDEFh
to decimal (i.e. switched base 16
to base 10
).
In binary system, the radix is 2
, so only digits 0
and 1
are used.
Here is the conversion of binary number 1010b
to decimal:
1 0 1 0 radix ^ i
│ │ │ │ ──────────────
│ │ │ └── ones 2 ^ 0 = 1
│ │ └───── twos 2 ^ 1 = 2
│ └──────── fours 2 ^ 2 = 4
└─────────── eights 2 ^ 3 = 8
ones twos fours eights
───────────────────────────────────────────────
(0 * 1) + (1 * 2) + (0 * 4) + (1 * 8)
= 0 + 2 + 0 + 8
= 10
Octal system - same thing, radix is 8
, digits 0...7
are in use.
Converting octal 04567
to decimal:
4 5 6 7 radix ^ i
│ │ │ │ ──────────────
│ │ │ └── ones 8 ^ 0 = 1
│ │ └───── eights 8 ^ 1 = 8
│ └──────── 64:s 8 ^ 2 = 64
└─────────── 512:s 8 ^ 3 = 512
ones eights 64:s 512:s
───────────────────────────────────────────────
(7 * 1) + (6 * 8) + (5 * 64) + (4 * 512)
= 7 + 48 + 320 + 2048
= 2423
So, to do a conversion between number systems is to simply change the radix.
To learn about bitwise operators, see http://www.eskimo.com/~scs/cclass/int/sx4ab.html.
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