This document discusses different types of control structures used in algorithms including: 1. Sequence, binary selection, multiway selection, and iteration which are matched to descriptions. Binary selection involves two choices, multiway selection allows more than two choices, and iteration repeats instructions. 2. Control structures like sequence, iteration/repetition, and selection (binary and multiway) are identified in sample algorithms involving counting loops and conditional statements. 3. The last part asks to identify the control structure other than sequence used in additional sample algorithms.

1. Algorithms Sheet 2
Identifying Control Structures

2. 1. Match the terms sequence, binary
selection, multiway selection and
iteration to the descriptions that follow:
(a) a decision taken in an algorithm which can
go either of two ways
binary selection
(b) decision taken in an algorithm which allows
decision
more than two choices
more than two
multiway selection

3. 1. Match the terms sequence, binary
selection, multiway selection and
iteration to the descriptions that follow:
decision
(a) a decision taken in the processing done by an ATM
to either withdraw, deposit or check account balance,
depending on the key pressed more than two
multiway selection
(d) a loop in a process which repeats the same
repeats
instructions a number of times
iteration

4. 1. Match the terms sequence, binary
selection, multiway selection and
iteration to the descriptions that follow:
always
(e) a part of a program where we always add 1 to
a counter and then print
sequence
(f) a portion of a program that is done over and
over and
over again and only stops when the count
over again,
reaches zero
iteration

5. 2. Identify two of the control structures
used in each of the following algorithms
(a)
Count = 0 sequence
REPEAT iteration/repetition
DoTheLoop
Add 1 to Count sequence
UNTIL Count = 5

6. 2. Identify two of the control structures
used in each of the following algorithms
(b)
WHILE Count <= 5 iteration/repetition
Add 1 to Count sequence
DoTheLoop
END WHILE

7. 2. Identify two of the control structures
used in each of the following algorithms
(c)
Get NextVideo sequence
IF category = ‘X’ selection (binary)
THEN print ‘You cannot watch this!’
ELSE DoBorrowProcess
Print details
END IF

8. 2. Identify two of the control structures
used in each of the following algorithms
(d)
REPEAT iteration/repetition
Enter Number sequence
IF Number > highest selection
THEN set highest to Number
END IF
UNTIL no more Numbers

9. 2. Identify two of the control structures
used in each of the following algorithms
(e)
WHILE more input iteration/repetition
Select input selection (multiway)
CASE 1
DoWithdrawals
CASE 2
DoDeposits
CASE 3
DoAccountBalance
CASE other
DoErrorProcess
END select
Get input sequence
END WHILE

10. 3.
Identify the
control structure
other than
sequence
used in the
following
algorithms:

11. 3.
Identify the
control structure
other than
sequence
used in the
following
algorithms:

12. 3.
Identify the
control structure
other than
sequence
used in the
following
algorithms:

13. 3.
Identify the
control structure
other than
sequence
used in the
following
algorithms:

14. Remember
You need to know how to apply
this information, so see me for
further help if you think it is
necessary for you.