082-Engineering-Mathematics-Anthony-Croft-Robert-Davison-Martin-Hargreaves-James-Flint-Edisi-5-2017

1.3 Number bases 11
Solutions
1 (a) 8 (b) 9 (c) 5 (d) 361
1 1
(e) 4 (f) (g) (h) 3
16 2
(i) 8 (j) 0.1 (k) 27
2 (a) 15.8489 (b) 0.2853
(c) 88.1816 (d) 3.8159
3 (a) x 11 (b) −x 3 (c) x
1 1 1
(d) (e)
x x 8 (f)
x 12
4 (a) x 1/6 (b) 2x (c)
(d)
1
2x
3
y
(e) ab 3 c 2 (f) 16t 2
1.3 NUMBERBASES
The decimal system of numbers in common use is based on the 10 digits 0, 1, 2, 3, 4,
5, 6, 7, 8 and 9. However, other number systems have important applications in computerscienceandelectronicengineering.Inthissectionweremindthereaderofwhatis
meant by a number in the decimal system, and show how we can use powers or indices
with bases of 2 and 16 to represent numbers in the binary and hexadecimal systems
respectively.Wefollowthisbyanexplanationofanalternativebinaryrepresentationof
a number known as binarycoded decimal.
1.3.1 Thedecimalsystem
Thenumbersthatwecommonlyuseineverydaylifearebasedon10.Forexample,253
can bewrittenas
253=200+50+3
= 2(100) + 5(10) + 3(1)
= 2(10 2 ) + 5(10 1 ) + 3(10 0 )
In this form it is clear why we refer to this as a ‘base 10’ number. When we use 10 as a
basewesaywearewritinginthedecimalsystem.Notethatinthedecimalsystemthere
are10digits:0,1,2,3,4,5,6,7,8,and9.Youmayrecallthephrase‘hundreds,tensand
units’ and as we have seen these are simply powers of 10. To avoid possible confusion
with numbers using other bases, we denote numbers in base 10 with a small subscript,
forexample, 5192 10
:
5192 10
= 5000 +100 +90 +2
= 5(1000) + 1(100) + 9(10) + 2(1)
= 5(10 3 ) + 1(10 2 ) + 9(10 1 ) + 2(10 0 )
Notethat,inthepreviousline,aswemovefromrighttoleft,thepowersof10increase.
1.3.2 Thebinarysystem
Abinarysystemusesthenumber2foritsbase.Abinarysystemhasonlytwodigits,0
and 1, and these are called binary digits or simply bits. Binary numbers are based on
powersof2.Inacomputer,binarynumbersareusuallystoredingroupsof8bitswhich
wecall abyte.