Download Topic 3 - Smooth Operators Fact Sheet

Topic 3 – Fact Sheets
Pseudocode
Pseudocode is a type of simplified code that represents a programming language used to write
algorithms (an algorithm is a logical sequence of steps for performing an action). Using pseudocode
makes it easier to work out a problem and find solutions before coding is used.
Pseudocode does not have a specific syntax and is not a programming language but is a simplified form
of code that helps to simplify problems in the planning stages of a program. Pseudocode uses standard
tags (called notations) such as:





INPUT – user should enter some text (e.g. INPUT "user inputs name")
OUTPUT – this indicates something that is output to screen (e.g. OUTPUT "Welcome, Bod!")
WHILE – this is used to repeatedly request information until a condition has been met and is
referred to as a condition-controlled loop (see Topic 2)
FOR – this is used within count-controlled loops and will be repeated subject to the range (see
Topic 2)
IF, THEN, ELSE – used to test a statement and make a decision
If we want to write a program that will ask for the user's name and return a welcome message, the
pseudocode may look like this:
OUTPUT "Enter your password"
INPUT user inputs password
STORE password in password variable
IF password = "Bod1" THEN
OUTPUT "Welcome Bod"
ELSE
OUTPUT "Incorrect! Please re-enter password to proceed"
Conditions – True or False
A condition is a statement or calculation which is either true or false. For example, the following
statement '1 is greater than 2' is false, whereas the statement '2 is greater than 1' is true.
Statements can use operators such as AND, OR and NOT. For example, ‘1 is greater than 2 AND 2 is
greater than 1' makes a false statement. The statement '1 is greater than 2 OR 2 is greater than 1'
makes a TRUE statement because one of the conditions is true. The NOT operator can be used to refine
statements further. For example, 'Chester NOT Liverpool' will find data that matches the Chester
criterion and not Liverpool.
Expressions
In programming there are expressions, operators and conditions. The greater than expression is
expressed as the operator > (e.g. 2 > 1). This statement uses a comparison to compare the numbers and
makes a decision based on the criteria. As Boolean is based on algebra, numbers can be represented as
letters (called variables because the value is subject to change); for example, x > y where x is 2 and y is 1.
Boolean operators vary in different languages, such as Python.
KS3 Computing Activity Worksheets (Fact Sheets)Page 1 of 3
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Expression
Equals
Greater than
Comparison operator
=
>
Less than
<
Greater than or equal to
>=
Less than or equal to
Does not equal
Expression
And
Or
Not
<=
<>
Boolean operator
AND
OR
NOT
Python
==
!=
Python
and
or
not
Truth Tables and Logic Gates
Truth tables help you to see how the input of a logic gate relates to its output using the Boolean
operators AND, OR and NOT. Logic gates are switches within circuits which are either TRUE = 1 or
FALSE = 0.
AND = each input must match criteria
OR = one or both inputs must match criteria
NOT = output is opposite of input
Example of truth table using Boolean operator AND where A AND B equal Z:
A
0
1
1
0
B
0
0
1
1
Z
0
0
1
0
Example of truth table using Boolean operator OR where A OR B equal Z:
A
0
1
0
1
B
0
0
1
1
Z
0
1
1
1
Example of truth table using Boolean operator NOT where A is NOT equal to Z:
A
0
1
Z
1
0
KS3 Computing Activity Worksheets (Fact Sheets)Page 2 of 3
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Examples of logic gates:
AND gate: X AND Z must each meet the criteria Y otherwise FALSE (0)
X
Y
Z
Look at the example below of a truth table that has been turned into a logic gate where A DOES NOT
EQUAL Z
A
0
Z
1
NOT gate:
Output is opposite of input
A
Z
OR gate:
One or both inputs must match criteria
A
Y
Z
KS3 Computing Activity Worksheets (Fact Sheets)Page 3 of 3
© ZigZag Education, 2016