Stretch tasks Algorithms, Flowcharts and Pseudocode

Round 1: Quiz Blitz

1. A diamond A diamond holds a condition with two labelled outputs.
2. A parallelogram Reading data in and sending data out both use a parallelogram.
3. 10 1 + 2 + 3 + 4 = 10.
4. SET x TO 5 Assignment is SET ... TO.
5. True It tests its condition after the body.
6. False It tests first, so it can run zero times.
7. Hello Priya & joins values together.
8. Returns a value A function uses RETURN. A procedure does a job and returns nothing.
9. Not equal to = compares for equality and <> for not equal.
10. A column for each variable; A new row every time a value changes The history of values is the working, and the working earns marks.
11. 7 Indices start at 0, so scores[1] is the second element.
12. Inside, it would reset on every pass A total set to 0 inside the loop loses everything added so far.

Round 2: Quick Fire

1. • An algorithm is a sequence of steps, in any form
   • A program is an algorithm written in a programming language so a computer can run it
   Model answer

   An algorithm is a precise sequence of steps that solves a problem, which can be written as a flowchart or pseudocode. A program is an algorithm written in a particular programming language, such as Python, so that a computer can run it.

2. • WHILE tests its condition before the body, so it may run zero times
   • REPEAT ... UNTIL tests after the body, so it always runs at least once
   Model answer

   A WHILE loop tests its condition before the body, so it can run zero times. A REPEAT ... UNTIL loop tests its condition after the body, so it always runs at least once.

3. • The password is only read once, so the condition never changes
   • Add a RECEIVE inside the loop
   Model answer

   The password is only read once, before the loop, so inside the loop it never changes and the condition stays true forever. A RECEIVE password FROM (STRING) KEYBOARD line must be added inside the loop, so the user is asked again on every pass.

4. • One column for each variable, and for output
   • A new row every time a value changes, never overwriting
   • Work one line at a time, using the current values
   Model answer

   Draw one column for each variable and one for output, and write the starting values in the first row. Work through the algorithm one line at a time, adding a new row every time a value changes rather than overwriting it, so the working shows even if one value is wrong.

Round 3: Big Think

1. • A loop that runs 10 times
   • RECEIVE a number inside the loop
   • Set the total to 0 before the loop
   • Add each number to the total
   • Test whether the number is below 0
   • Add 1 to a count of negatives
   • Send the total to the display after the loop
   • Send the count of negatives to the display
   Model answer

   PSEUDOCODECopy

   SET total TO 0
   SET negatives TO 0
   FOR index FROM 1 TO 10 DO
       RECEIVE number FROM (INTEGER) KEYBOARD
       SET total TO total + number
       IF number < 0 THEN
           SET negatives TO negatives + 1
       END IF
   END FOR
   SEND total TO DISPLAY
   SEND negatives TO DISPLAY

2. • A diamond must hold a condition, not a statement
   • Such as attempts < 3
   • The statement belongs in a process rectangle
   • Both branches must be labelled Yes and No
   • Otherwise nobody can tell which way the algorithm goes
   • The loop arrow must rejoin above the input
   • Otherwise the same wrong password is tested forever
   • So the user is asked again each time
   Model answer

   A decision diamond must contain a condition with two possible answers, such as attempts < 3, not a statement. The statement 'add one to attempts' belongs in a process rectangle. Both branches out of the diamond must be labelled Yes and No, otherwise nobody can tell which way the algorithm goes. The loop arrow must rejoin above the input, so the user is asked again each time. Rejoining below the input means the same wrong password is tested forever.

This or That

1. A rounded rectangle The terminal symbol is a rounded rectangle, one at each end.
2. WHILE WHILE tests first. REPEAT tests after the body, so it always runs once.
3. FOREACH FOREACH visits each element of a data structure in turn.
4. Edexcel OCR writes print(total). Edexcel writes SEND ... TO DISPLAY.
5. A function A procedure does a job but returns nothing.
6. Above the input Rejoining below the input tests the same value forever.
7. 3 Indices start at 0, so scores[3] is the fourth element.
8. Add a new row The history is the working, and the working earns the marks.

Memory Match

• A 2 Algorithm: Precise steps that always finish
• B 4 Trace table: Records each variable after every step
• C 6 Decision symbol: A diamond holding a condition
• D 3 Terminal symbol: Rounded rectangle for START and STOP
• E 1 Function: A subprogram that returns a value
• F 5 Procedure: A subprogram that returns nothing

Sort It

1. Terminal STOP STOP sits in a rounded rectangle too.
2. Terminal START START sits in a rounded rectangle.
3. Input or output Read the password Reading data in uses a parallelogram.
4. Input or output Enter the user's age Input uses a parallelogram.
5. Input or output Display 'Access granted' Sending data out uses a parallelogram.
6. Process Set count to 0 An assignment is a process.
7. Input or output Print the total Output uses a parallelogram.
8. Process Add one to attempts A statement belongs in a process box, never a diamond.
9. Decision age >= 18? A comparison is a decision.
10. Process total = total + price A calculation is a process rectangle.
11. Decision Is the password correct? A yes or no question is a decision.
12. Decision count > 10? A condition with two answers goes in a diamond.