b_book1.gif (162 bytes) Data - Coding systems
b_html1.gif (183 bytes)Numeric EBCDIC

Encoding text data - EBCDIC

Extended character set
With Third Generation computers (1960's) came the request for :-
  • Word Processing - Lowercase (a..z)
  • Data Communications - Control Characters

A 7 bit code gives a range of 128 characters, satisfying these two requirements.

  • EBCDIC Extended Binary Coded Data Interchange Code.
  • Has a code for every number, character, and sign, including unprintable characters such as FORM FEED, BACKSPACE etc.
  • Different codes from ASCII, so cannot be used on the same machine as ASCII.

EBCDIC - Extended Binary Coded Decimal Interchange Code
IBM developed a 9 bit code for representing characters. This code is primarily used by mini and mainframe computer systems. All characters are represented using 8 bit positions, plus a check bit. The eight bit positions are divided into a zone portion (four bits) and numeric portion (four bits). With 8 bits 256 characters may be represented. These include upper and lowercase letters, numeric digits, special characters (*,&,$, etc), and certain control characters (eg Bell)

Example D,d,$

Check Bit

| Zone Portion | Numeric Portion

C

| Z | Z | Z | Z | 8 | 4 | 2 | 1
| 1 | 1 | 0 | 0
| 1 | 0 | 0 | 0
| 0 | 1 | 0 | 1 		| 0 | 1 | 0 | 0
| 0 | 1 | 0 | 0
| 1 | 0 | 1 | 1		 11000100 = D
10000100 = d
01011011 = $

The unit of eight bits is commonly called a byte, and is usually the smallest addressable unit of information in a computer.

EBCDIC table

The following table illustrates a subset of the EBCDIC code.

Ch Hex

Ch Hex

Ch Hex

Ch Hex

Ch Hex

Ch Hex

Ch Hex

<space>40
. 4B
< 4C
( 4D
+ 4E
| 4F
& 50
! 5A
$ 5B
* 5C
) 5D
; 5E
' 5F

- 60
/ 61
, 6B
% 6C
6D
> 6E
? 6F
\ 79
: 7A
# 7B
@ 7C
' 7D
= 7E
" 7F

a 81
b 82
c 83
d 84
e 85
f 86
g 87
h 88
i 89
j 91
k 92
l 93
m 94

n 95
o 96
q 98
r 99
s A2
t A3
u A4
v A5
w A6
x A7
y A8
z A9
{ C0

A C1
B C2
C C3
D C4
E C5
F C6
G C7
H C8
I C9
J D1
K D2
L D3
M D4

N D5
O D6
P D7
Q D8
R D9
S E2
T E3
U E4
V E5
W E6
X E7
Y E8
Z E9

0 F0
1 F1
2 F2
3 F3
4 F4
5 F5
6 F6
7 F7
8 F8
9 F9

Exercise 1

Decode the following advertisement:

COMPUTER PERSONNEL

E5C1C3C1D5C3C9C5E240C5E7C9E2E340E3C8D9D6E

4C7C8D6E4E340D5C5E640E9C5C1D3C1D5C440C6D6D9

40C5E7D7C5D9C9C5D5C3C5C440D7D9D6C7D9C1D4D4

C5D9E240C1D5C440C1D5C1D3E8E2E3E24B40C6D6D9

40C6E4D9E3C8C5D940C4C5E3C1C9D3E240C7C9E5C5

40C4C1E5C540E6C1D2C5D5E2C9C1E640C140C3C1D3

D340D5D6E640D6D540E6C7E3D540F7F2F160F1F5F1

4B40C1D3D340C1D7D7D3C9C3C1E3C9D6D5E240C1D9

C540E3D9C5C1E3C5C440C9D540E3C8C540E2E3D9C9

C3E3C5E2E340C3D6D5C6C9C4C5D5C3C54B4040404C

C9C4D7C540D7C5D9E2D6D5D5C5D340E2C5D9E5C9

C3C5E240D3E3C44B

Advertisement in the Evening Post, May 1981

 

Answers

Answer 1

Vacancies exist throughout New Zealand for experienced programmers and analysts. For further details give Dave Waikinsaw a call now on Wgtn 721-151. ALL Personnel Services Ltd.

[Rev 9/9/98] 27/4/97 © 1997-98 V/2-Com (Verhaart), P O Box 8415, Havelock North, New Zealand.