Roles of variables represent tacit knowledge, i.e., knowledge that experts have but cannot articulate unless especially prompted to do so. As a consequence, even though you - as an expert - know the roles, you do not know that you know. In particular, even though you know what a counter - a special case of the role stepper - is, the names of many roles are not immediately clear and the recognition of the role of a variable is at first not obvious.
This page contains example programs that can be used to familiarize oneself with the role concept and the names of roles so that this tacit knowledge becomes more available. You can do this by identifying the role of each variable in the following programs yourself. Our interpretations are provided on a separate page.
program squares (input, output);
(* Print two squares *)
var distance : integer; (* Distance between squares *)
begin
write('Enter the distance between squares: '); readln(distance);
writeln;
writeln('***', ' ' : distance, '***');
writeln('* *', ' ' : distance, '* *');
writeln('***', ' ' : distance, '***')
end.
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Determine appropriate role for
each of the variables:
| Possible roles are: |
program time (input, output);
(* Transform time to seconds *)
type
hour = 0..23;
minute = 0..59
second = 0..59;
var hours : hour; (* Hour of the time *)
mins : minute; (* Minute of the time *)
secs : second; (* Second of the time *)
begin
write('Enter time (hour min sec , e.g., 13 30 5): ');
readln(hours, mins, secs);
writeln ('At ', hours : 2, '.', mins : 2, '.',
secs : 2, secs + (60 * (mins + 60 * hours)) : 6,
' seconds has elapsed.')
end.
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Determine appropriate role for
each of the variables:
| Possible roles are: |
program multiplication (input, output);
(* Print a multiplication table *)
var size, (* Size of table *)
row, (* Row index *)
col: integer; (* Column index *)
begin
write('Enter size: '); readln(size);
writeln (' ' : 15, 'Multiplication table ');
write (' ' : 4);
for col := 1 to 10 do write(col : 4);
writeln;
for row := 1 to size do begin
write(row : 4);
for col := 1 to 10 do write(row*col : 4);
writeln
end
end.
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Determine appropriate role for
each of the variables:
| Possible roles are: |
program occur (input, output);
(* Count occurences of a value in an array *)
const
last = 7;
type
ArrayType = array [1..last] of integer;
var
value: ArrayType; (* Array of values *)
i, (* Array index *)
key, (* Value to search for *)
count: integer; (* Count of occurences *)
begin
writeln('Enter ', last, ' values: ');
for i := 1 to last do read(value[i]);
readln;
write('Enter value to search for: ');
readln(key);
count := 0;
for i := 1 to last do
if value[i] = key then count := count + 1;
writeln('There are ', count, ' occurences of ',
key, ' in the array');
end.
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Determine appropriate role for
each of the variables:
| Possible roles are: |
program square (input, output);
(* Drawing a square *)
const maxSide = 78; (* Max length for sides *)
var character : char; (* Character to be used for drawing *)
side, (* Length of sides *)
i, j : integer; (* Counters for side lengths *)
begin
write('Enter character for drawing: '); readln(character);
write('Enter side length : '); readln(side);
while (side < 1) or (side > maxSide) do begin
writeln('Length incorrect. Re-enter: '); readln(side)
end;
writeln;
for i := 1 to side do begin
for j := 1 to side do write(character);
writeln
end
end.
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Determine appropriate role for
each of the variables:
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program histogram (input, output);
(* Draw a histogram *)
const longest = 40; (* Longest bar *)
var amount : array [1..12] of real; (* Data for drawing *)
max : real; (* Maximum data element *)
month, (* Current month *)
i : integer;
begin
for month := 1 to 12 do begin
write('Enter amount for month ', month : 2, ': ');
readln(amount[month]);
if i = 1 then max := amount[1]
else if max < amount[month] then max := amount[month]
end;
writeln;
for month := 1 to 12 do begin
write(month : 2, ': ');
for i := 1 to round(amount[month] / max * longest)
do write('*');
writeln
end
end.
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Determine appropriate role for
each of the variables:
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program diceGame (input, output);
(* Simulate a dice game. *)
var die1, die2, (* Values of dice thrown *)
total1, total2: integer; (* Sums of values of each player *)
firstPlayer: boolean; (* First player's turn ? *)
begin
Randomize;
total1 := 0;
total2 := 0;
firstPlayer := True;
while (total1 < 100) and (total2 < 100) do begin
die1 := Random(6) + 1;
die2 := Random(6) + 1;
if firstPlayer then write('First') else write('Second');
writeln(' player throws: ', die1, die2);
if firstPlayer then
total1 := total1 + die1 + die2
else
total2 := total2 + die1 + die2;
firstPlayer := not firstPlayer;
end;
write('Player ');
if total1 > total2 then write('First') else write('Second');
write(' player won the game.')
end.
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Determine appropriate role for
each of the variables:
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program closest (input, output);
(* Find the closest number *)
var original, (* Closest to this one *)
data, (* Current input data *)
closest: integer; (* Closest found so far *)
begin
write('Enter any number: '); readln(original);
write('Enter a positive number (negative to end): ');
readln(data);
closest := data;
while data >= 0 do begin
if abs(data-original) < abs(closest-original)
then closest := data;
write('Enter a positive number (negative to end): ');
readln(data);
end;
if closest < 0
then writeln('No positive value entered.')
else writeln('The closest to ', original, ' was ', closest)
end.
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Determine appropriate role for
each of the variables:
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program growth (input, output);
(* Growth of capital on a bank account *)
var capital, (* Capital on the bank account *)
percent, (* Interest rate *)
factor, (* Factor for yearly growth *)
interest: real; (* Interest in current year *)
years, (* Time to consider *)
i : integer; (* Year counter *)
inputOk : Boolean; (* Is input valid ? *)
begin
write('Enter capital (positive or negative): '); readln(capital);
inputOk := false;
while not inputOk do begin
write('Enter interest rate (%): '); readln(percent);
write('Enter time (years) : '); readln(years);
inputOk := (percent > 0) and (years > 0);
if not inputOk then begin
writeln;
writeln('Invalid data. Re-enter.')
end
end;
writeln;
factor := percent / 100;
for i := 1 to years do begin
interest := capital * factor;
capital := capital + interest;
writeln('After ', i : 2, 'years: interest is ',
interest : 11 : 2,
' and total capital is ', capital : 12 : 2)
end
end.
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Determine appropriate role for
each of the variables:
| Possible roles are: |
program saw (input, output);
(* Read a sequence of values and check if they form a 'saw':
adjacent values go up and then down. *)
const
last = 7;
type
ArrayType = array [1..last] of integer;
var value: ArrayType; (* Values to be checked *)
i: integer; (* Index of array *)
up, (* Current direction is up ? *)
Ok: Boolean; (* Does saw property still hold ? *)
begin
writeln('Enter ', last, ' values:');
for i:=1 to last do read(value[i]);
up := value[1] < value[2];
Ok := value[1] <> value[2];
i := 2;
while Ok and (i < last) do begin
Ok := (up and (value[i] > value[i+1])) or
(not up and (value[i] < value[i+1]));
up := not up;
i := i + 1
end;
write('Values ');
if not Ok then write('do not ');
writeln('form a saw.')
end.
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Determine appropriate role for
each of the variables:
| Possible roles are: |
program smoothedAverage (input, output);
(* Largest average of three consecutive months *)
var month: integer; (* Current month *)
current, previous, preceding, (* Data for three months *)
average, (* Current average *)
largest: real; (* Largest one found so far *)
begin
write('Enter 1. value: '); readln(preceding);
write('Enter 2. value: '); readln(previous);
write('Enter 3. value: '); readln(current);
largest := (current + previous + preceding) / 3;
for month := 4 to 12 do begin
preceding := previous;
previous := current;
write('Enter ', month, '. value: '); readln(current);
average := (current + previous + preceding) / 3;
if average > largest then largest := average
end;
writeln('Largest three month average was ', largest)
end.
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Determine appropriate role for
each of the variables:
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program number (input, output);
(* Read a number with embedded commas, e.g., 123,456 *)
const
sep = ',';
var c: char; (* The character read *)
val: integer; (* Accumulated value of number *)
begin
val := 0;
write('Enter number: ');
read(c);
while ((c >= '0') and (c <= '9')) or (c = sep) do begin
if c <> sep
then val := val * 10 + ord(c) - ord('0');
read(c)
end;
writeln('Value is ', val)
end.
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Determine appropriate role for
each of the variables:
| Possible roles are: |
Last updated: February 8, 2006