The document discusses different types of loop structures used in problem solving with loops, including while/while-end loops, repeat/until loops, and automatic counter loops. It also covers topics like incrementing, accumulating, nested loops, indicators, and recursion. Flowcharts and algorithms are provided as examples to illustrate the various loop structures.

1. Data Structures and Algorithms
Problem Solving
with Loops
The Loop Logic Structure
A third logic structure for designing decisions is the
loop structure. The loop logic structure is the repeating
structure.
Types of Loop Structures
@ WHILE / WHILE-END
@ REPEAT / UNTIL
@ AUTOMATIC COUNTER LOOP
Incrementing
The task of incrementing, or counting, is done by
adding a constant, such as 1 or 2, to the value of a
variable. To write the instruction to increment a
variable, you use an assignment statement. For
example:
COUNTER = COUNTER + 1 or C = C+ 1
Problem Solving with Loops *Property of STI
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2. Data Structures and Algorithms
Problem Solving
with Loops
Accumulating
Another task that a program must often perform is
accumulating, or summing a group of numbers. The
process of accumulating is similar to incrementing,
except a variable instead of a constant is added to
another variable, which holds the value of the sum or
total. The instruction for accumulating is the
following :
SUM = SUM + VARIABLE
PRODUCT = PRODUCT * NUMBER
Problem Solving with Loops *Property of STI
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3. Data Structures and Algorithms
Problem Solving
with Loops
WHILE / WHILE - END
The first of the three types of loop structures is the
WHILE/WHILE-END structure. This type of loop tells
the computer that while the condition is TRUE, repeat
all instructions between the WHILE and the WHILE-
END. The form of the algorithm is the following:
WHILE <CONDITION(S)>
INSTRUCTION
INSTRUCTION
.
.
.
WHILE-END
Problem Solving with Loops *Property of STI
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4. Data Structures and Algorithms
Problem Solving
with Loops
Flowchart Diagram of WHILE/WHILE-END
Problem Solving with Loops *Property of STI
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5. Data Structures and Algorithms
Problem Solving
with Loops
Decision Equivalent to WHILE/WHILE-END
Problem Solving with Loops *Property of STI
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6. Data Structures and Algorithms
Problem Solving
with Loops
Problem : Create the algorithm and the flowchart to
find the average age of all the students in a class.
Problem Solving with Loops *Property of STI
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7. Data Structures and Algorithms
Problem Solving
with Loops
Repeat/Until
The second type of loop structure is the REPEAT/UNTIL
structure. This type of loop tells the computer to
repeat the set of instructions between the REPEAT and
the until, until a condition is TRUE. The format of the
REPEAT/UNTIL algorithm is the following:
Repeat
Instruction
Instruction
.
.
.
Until <condition(s)>
Problem Solving with Loops *Property of STI
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8. Data Structures and Algorithms
Problem Solving
with Loops
Flowchart Diagram of REPEAT/UNTIL
Problem Solving with Loops *Property of STI
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9. Data Structures and Algorithms
Problem Solving
with Loops
Decision Equivalent to REPEAT/UNTIL
Problem Solving with Loops *Property of STI
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10. Data Structures and Algorithms
Problem Solving
with Loops
Problem : Create the algorithm and the flowchart to
find the average age of all the students in a class.
Problem Solving with Loops *Property of STI
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11. Data Structures and Algorithms
Problem Solving
with Loops
Automatic – Counter Loop
The third type of loop structure is the automatic-
counter loop. This type of loop increments or
decrements a variable each time the loop is repeated.
The form of the algorithm for the automatic counter-
loop is the following :
LOOP:COUNTER = BEGIN TO END STEP S
INSTRUCTION
INSTRUCTION
.
.
.
LOOP-END: COUNTER
Problem Solving with Loops *Property of STI
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12. Data Structures and Algorithms
Problem Solving
with Loops
Decision Equivalent to Automatic-Counter Loop
Problem Solving with Loops *Property of STI
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13. Data Structures and Algorithms
Problem Solving
with Loops
Problem : Create the algorithm and the flowchart to
find the average age of all the students in a class.
Problem Solving with Loops *Property of STI
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14. Data Structures and Algorithms
Problem Solving
with Loops
Nested Loops
Loops can be nested like decisions can. Each loop must
be nested inside the loop just outside it. The general
rules regarding loops, such as where the condition is
processed and how indentation and brackets are used,
hold true for nested loops as well as single loops.
The inner loops do not have to be the same types of
loop structures as the outer loops; that is, a WHILE/
WHILE-END may be nested inside a REPEAT/UNTIL loop,
or vice versa.
Problem Solving with Loops *Property of STI
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15. Data Structures and Algorithms
Problem Solving
with Loops
Nested Loops
Problem Solving with Loops *Property of STI
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16. Data Structures and Algorithms
Problem Solving
with Loops
Problem Solving with Loops *Property of STI
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17. Data Structures and Algorithms
Problem Solving
with Loops
Indicators
Indicators – are logical variables that a programmer
sets within a program to change the processing path
or to control when the processing of a loop should end.
They are sometimes called flags, switches, or trip
values.
Recursion
Another type of loop structure is recursion. Recursion
occurs when a module or a function calls itself.
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18. Data Structures and Algorithms
Problem Solving
with Loops
Problem Solving with Loops *Property of STI
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