URL encoding

Web addresses can be written using hexadecimal rather than denary. Hexadecimal codes are preceded by a % sign. For example, the word “www.ruknuddin.com” is written as:

r           u          k          n          u          d          d          i           n         

in hex             %72    %75    %6B    %6E    %75    %64    %64    %69    %6E

w

w

w

.

r

u

k

n

u

d

d

i

n

.

c

o

m

%77

%77

%77

%2E

%72

%75

%6B

%6E

%75

%64

%64

%69

%6E

%2E

%63

%6F

%6D

Some characters are not allowed in URL. URL encoding converts characters into a format that can be transmitted over the Internet.

For example

Ø  %20 – is used in URL in place of <space> not allowed in a URL, %20 is the coding for a space (32 in denary)

Ø ? – separates the URL from all parameters or variables

e.g. for query to search inqilab patel in Google

https://www.google.com.pk/search?q=inqilab%20patel

here “q” is variable for query “?” separates it from URL “https://www.google.com.pk/search”

while“%20”  is used for the space between “inqilab” and “patel” and

? to separate   Variable from URL

 Example Question 2:

Consider the URL:

http://cie.org.uk/computerscience.html

(i) Give the meaning of the following parts of the URL.

http ....................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
cie.org.uk ...........................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
computerscience.html .......................................................................................................
...........................................................................................................................................
....................................................................................................................................... [3]
(ii) Sometimes the URL contains the characters %20 and ?.

Describe the function of these characters.

%20 ...................................................................................................................................
...........................................................................................................................................
? ........................................................................................................................................
...................................................................................................................................... [2]

Characters can be represented in a computer by a numerical code.
The following list shows 16 characters with their numerical codes in denary:

a = 97             d = 100           h = 104           m = 109          t = 116
b = 98             e = 101           i = 105            o = 111           u = 117
c = 99             g = 103           k = 107           r = 114            w = 119

. = 46 (code for the full stop)

Web addresses can be written using hexadecimal rather than denary. Hexadecimal codes are preceded by a % sign. For example, the word “c a g e” is written as:

either              99        97        103     101    (in denary)

or                     %63   %61    %67    %65    (in hexadecimal)
(a) Complete the conversion of the following web address into hexadecimal: [3]

w

w

w

.

c

i

e

.

o

r

g

.

u

K

%77

%77

%77

b) Complete the web address from the given hexadecimal codes: [3]

%77	%77	%77	%2E	%72	%6F	%63	%6B	%69	%63	%74	%2E	%63	%6F	%6D
w	w	w