How does this program to count vowels work? - pascal

Question

I want to understand this code, especially PROCEDURE
PROGRAM vowels;
USES crt;
{Program that counts the number of vowels in a sentence}
CONST space=' ';
maxchar=80;
TYPE vowel=(a,e,i,o,u);
VAR buffer:ARRAY[1..maxchar] of char;
vowelcount:ARRAY[vowel] of integer;
PROCEDURE initialize;
VAR ch:vowel;
BEGIN
FOR ch:=a TO u DO
BEGIN
vowelcount[ch]:=0;
END;
END;
PROCEDURE textinput;
VAR index:integer;
BEGIN
writeln('Input a sentence');
FOR index:=1 TO maxchar DO
IF eoln THEN buffer[index]:=space
ELSE read(buffer[index]);
readln;
END;
PROCEDURE analysis;
VAR index:integer;
ch:vowel;
BEGIN
index:=1;
WHILE index<>maxchar+1 DO
BEGIN
IF buffer[index] IN ['a','e','i','o','u'] THEN
BEGIN
CASE buffer[index] OF
'a':ch:=a;
'e':ch:=e;
'i':ch:=i;
'o':ch:=o;
'u':ch:=u;
END;
vowelcount[ch]:=vowelcount[ch]+1;
END;
index:=index+1;
END;
END;
PROCEDURE vowelout;
VAR ch:vowel;
BEGIN
clrscr;
writeln;
writeln(' a e i o u');
FOR ch:=a TO u DO
write(vowelcount[ch]:4);
writeln;
END;
BEGIN
initialize;
textinput;
analysis;
vowelout;
END;

Answer 1

Overall: Okay this code is counting the number of vowels supplied in the input string.
Lets Begin....
TYPE vowel=(a,e,i,o,u); VAR
buffer:ARRAY[1..maxchar] of char;
vowelcount:ARRAY[vowel] of integer;
This code is defining a list of the vowels in english (a,e,i,o,u).
PROCEDURE initialize; VAR ch:vowel;
BEGIN FOR ch:=a TO u DO BEGIN
vowelcount[ch]:=0; END; END;
It then defines a variable to collect the number of each vowel, called vowelcount. That variable is an array, looks sort of like this:
vowelcount[a]=0;
vowelcount[e]=0;
vowelcount[i]=0; #... etc
Then the procedure "Analysis" is defined. This takes the input from the screen (which will be called later on in the program) and steps through each letter in the input.
WHILE index<>maxchar+1 DO BEGIN IF
buffer[index] IN ['a','e','i','o','u']
THEN BEGIN CASE buffer[index] OF
'a':ch:=a; 'e':ch:=e; 'i':ch:=i;
'o':ch:=o; 'u':ch:=u; END;
If any of those letters happens to be in the list of letters than matches a vowel, then it will add one to the number in the vowelcount array above. (vowelcount[ch]:=vowelcount[ch]+1) where ch is the matched letter. As you can see this is only triggered if it is a valid vowel (IF buffer[index] IN ['a','e','i','o','u'] )
Finally. The main code of the program, or what is actually run:
BEGIN clrscr; writeln; writeln(' a e i
o u'); FOR ch:=a TO u DO
write(vowelcount[ch]:4); writeln; END;
BEGIN initialize; textinput; analysis;
vowelout; END.
This basically strings the application together, starting by clearing the screen (in a dos prompt) and then outputting the vowels onto the screen. It then adds some formatting and outputs the current count of vowelcount (as above).
It will then request your input and finally it will output the contents of vowelcount again, which has been updated with the vowelcounts from the input you made.