This document introduces different types of algorithms including sequences, selections, and iterations. Sequences present a list of instructions to follow in order. Selections use if/then/else statements to make choices or repeat instructions conditionally. There are two types of iterations: count-controlled loops that repeat a set number of times, and condition-controlled loops that repeat until a condition is met. Common iteration structures include for, while, do while, and repeat until loops. The document provides examples of each type of algorithm structure.

1. L.O: SWBAT INTRODUCTION
TO FLOW CHARTS.

2. Sequences:
The most basic algorithm uses sequences
to present a list of instructions to be
followed one after the other, step by step.
An algorithm is a plan, a set of step-by-step instructions that a
computer follows to solve a problem.
To solve the problem, the instructions have to be followed in the right
order.
If the instructions are not carried out in the right order, you won’t get
the result you expected!
1.Start
2.unlock the door
3.open the door
4.enter the room
5.switch on the light
6.close the door behind you
7.stop

3. Selection:
1. IF the door is locked, THEN
unlock the door, ELSE do
nothing (go to next instruction)
2. IF the door is closed, THEN
open the door, ELSE do nothing
3. Enter the room
4. IF the room is dark, THEN
switch on the light, ELSE do
nothing
5. Close the door behind you
A selection is used to make choices based on information.
An algorithm can be made more intelligent by using IF, THEN
and ELSE to repeat instructions or move to different parts of
the program.

4. Iteration
• Iteration is the process of looping or repeating
sections of a program.
• There are two types of iteration: count-controlled
and condition-controlled.
• Count-controlled loops repeat the same steps a
specific number of times,
• regardless of the outcome.
• But a condition-controlled loop will keep repeating
the steps over and over…and over…and over…and
over, until it gets a specific result.

5. For loop (Count-controlled loop)
• The count-controlled loop can be described as a
FOR loop. The program repeats the action FOR a
number of times.
Here is an example using pseudocode:
Make “count” = 0
For as long as “count” is in the range of 0 to 5
Print “I am in loop number: ” and the value
contained in “count” together on a line
Increment “count” by 1

6. Condition-controlled loops
A program could be made more intelligent by
programming it to avoid hazards. For
example, if the robot vehicle is 3 cm from the
edge of the table and you tell it to move
forwards 5 cm, it will drive off the edge of the
table. To stop this from happening, you might
write a condition-controlled loop like this:
move forward
repeat until (touching table edge)

7. WHILE loops
Condition-controlled loops are also called WHILE
loops or WHILE-ENDWHILE statements. A WHILE
loop code is repeated based on a certain
condition. The condition could be 'true' or 'false'.
The WHILE loop executes while a condition is
true. Whether the condition is met or not is
checked at the beginning of the loop. If the
condition is 'true' it repeats, if not then the code
is not executed.
For example, to stop the robot from driving off
the edge of a table, you might write a WHILE loop
like this:
Move forward WHILE I am not
touching the table edge

8. DO WHILE loops
A similar condition-controlled loop is a DO
WHILE loop. This method differs from a
WHILE condition-controlled loop in that the
condition is checked at the end of the loop. If
the condition is ‘true’, the loop repeats.
Thus, the code in the loop is executed at
least once.
count = 1
do
print(count)
count+=1
while count <4

9. REPEAT UNTIL loops
REPEAT UNTIL loops are condition-controlled
loops that are found in older languages such as
BASIC or PASCAL. The principal is the same as a
DO WHILE loop, in that the condition is checked
at the end of the loop, thus the behaviour is the
same. Consider this pseudo-code example:
count = 1
repeat
print(count)
count+=1
until count >3

10. Infinite loops
Condition-controlled loops can result in
intentional or unintentional infinite loops. If we
wanted to loop indefinitely, we could set a
condition that would never be met, thus iterating
infinitely. The following examples would result in
an infinite loop:

11. Infinite loops
WHILE:
count = 1
while count <>0:
print(count)
count +=1

12. Infinite loops
DO WHILE:
count = 1
do
print(count)
count+=1
while count <>0

13. Infinite loops
REPEAT UNTIL:
count = 1
repeat
print(count)
count+=1
until count =0