Programming – Pascal: Essential skills 1
 

Learning Outcomes:

•  Apply algorithms of counting, accumulating, swapping, searching, sorting and merging in writing programs.

 

Character handling

 

ASCII Character list (extract):

Character	ASCII
‘0’	48
‘1’	49
‘A’	65
‘a’	97

 

Functions:

ord(‘A’) à 65

chr(65) à ‘A’

 

Essential skills:

Convert uppercase to lowercase: chr(ord(‘A’)+32) or lowercase(‘A’)

Convert lowercase to uppercase: chr(ord(‘a’)-32) or upcase(‘a’)

Covert ‘1’ to 1: ord(‘1’)-48

Covert ‘A’ to 1: ord(‘A’)-64

 

Relevant past paper:

DSE ICT Elect B(SP-2017):  SP 2bc.

CE CIT Elect A(2005-2011): 2007 1a, 4bc. 2008 4ab.

 

Counting/Accumulating

 

var counter, i:integer; begin    counter:=0;                                        (* initiation *)    for i:= 1 to 5 do                 counter := counter +1      (* count the number of loops *) end.

 

Relevant past paper:

CE CIT Elect A(2005-2011): 2008 4d. 2010 3a.

 

Swapping

 

Suppose A[1] = 5, A[2] = 10.

var temp:integer;                            (* a temporary variable is usually needed *) begin    temp := A[1];    A[1] := A[2];    A[2] := temp end.

begin                                                  (* a temporary variable is not necessary for numbers *)    A[1] := A[1] + A[2];                            (* A[1] = 15 *)    A[2] := A[1] – A[2];                            (* A[2] = 15 – 10 = 5 *)    A[1] := A[1] – A[2]                             (* A[1] = 15 – 5 = 10 *) end.

Now A[1] = 10, A[2] = 5.

 

Relevant past paper:

DSE ICT Elect B(SP-2017):  SP 3abc.

CE CIT Elect A(2005-2011): 2010 2b. 2011 2a.