PseudocodeSkill Area 305.2

Materials Prepared by Dhimas Ruswanto, BMm

Lecture Overview

• Pseudocode• Pseudocode (Sequence)• Pseudocode (Selection)• Pseudocode (Iteration)• Examples

Pseudocode• Pseudocode consists of short,

English phrases used to explain specific tasks within a program’s algorithm.

Pseudocode• Used to provide an outline description of

the specification for the software module• Contain a natural language of

expressions embedded in syntactic structures taken from programming language– IF…THEN…ELSE– REPEAT..UNTIL

• Not intended to be executed by a computer, must be interpreted by people.

PSEUDOCODESEQUENCE

Pseudocode (Sequence)

• When we write programs, we assume that the computer executes the program starting at the beginning and working its way to the end.

• This is a basic assumption of all algorithm design.

• We call this SEQUENCE.

Pseudocode (Sequence)

• In pseudo-code it looks like this:Statement1;Statement2;Statement3;Statement4;Statement5;Statement6;Statement7;Statement8;

Pseudocode (Sequence)

• For example, for making a cup of tea:

Organise everything together;Plug in kettle;Put teabag in cup;Put water into kettle;Wait for kettle to boil;Add water to cup;Remove teabag with spoon/fork;Add milk and/or sugar;Serve;

Pseudocode (Sequence)

• Or as a program:BEGINPROGRAM MakeACupOfTea: Organise everything together; Plug in kettle; Put teabag in cup; Put water into kettle; Wait for kettle to boil; Add water to cup; Remove teabag with spoon/fork; Add milk and/or sugar; Serve;END.

PSEUDOCODESELECTION

Pseudocode (Selection)

• What if we want to make a choice– example, do we want to add sugar or not to

the tea? • We call this SELECTION.

Pseudocode (Selection)

• So, we could state this as:

IF (sugar is required) THEN add sugar; ELSE don’t add sugar;ENDIF;

Pseudocode (Selection)

• Or, in general:

IF (<CONDITION>) THEN <Statements>; ELSE <Statements>;ENDIF;

Pseudocode (Selection)

• Or to check which number is biggest:

IF (A > B) THEN Print A + “is bigger”; ELSE Print B + “is bigger”;ENDIF;

Pseudocode (Selection)

• Adding a selection statement in the program:BEGIN

PROGRAM MakeACupOfTea: Organise everything together; Plug in kettle; Put teabag in cup; Put water into kettle; Wait for kettle to boil; Add water to cup; Remove teabag with spoon/fork; Add milk; IF (sugar is required) THEN add sugar; ELSE do nothing; ENDIF; Serve;END.

PSEUDOCODEITERATION

Pseudocode (Iteration)

• What if we need to tell the computer to keep doing something until some condition occurs?

• Let’s say we wish to indicate that the you need to keep filling the kettle with water until it is full.

• We need a LOOP, or ITERATION.

Pseudocode (Iteration)

WHILE (a true condition)STATEMENTor STATEMENT BLOCK concluded with

ENDWHILE

REPEATstatementstatement

UNTIL (condition is true)FOR (starting state, final state, increment)

Statement

Statement ENDFOR

WHILE Loop

REPEAT UNTIL Loop

FOR Loop

Pseudocode (Iteration)

• So, we could state this as:WHILE (Kettle is not full) DO keep filling kettle;ENDWHILE;

• Or to print out the numbers 1 to 5:A = 1;WHILE(A > 5) DO Print A; A = A + 1;ENDWHILE;

What is the benefit of using loop?

Get first entryIf this is the required entry

Then write down phone numberElse get next entryIf this is the correct entry

then write done entryelse get next entry

if this is the correct entry

We may rewrite this as follows:

Get first entry;Call this entry N;WHILE N is NOT the required entryDO Get next entry;

Call this entry N;ENDWHILE;

Consider the problem of searching for an entry in a phone book with only condition:

Pseudocode (Iteration)

• Or as a program:

BEGINPROGRAM MakeACupOfTea: Organise everything together; Plug in kettle; Put teabag in cup; WHILE (Kettle is not full) DO keep filling kettle; ENDWHILE; Wait for kettle to boil; Add water to cup; Remove teabag with spoon/fork; Add milk; IF (sugar is required) THEN add sugar; ELSE do nothing; ENDIF; Serve;END

PSEUDOCODEEXAMPLES

Examples• So let’s say we want to express the following

algorithm:– Read in a number and print it out.

BEGINPROGRAM PrintNumber:Use variables: A OF TYPE Integer Read A; Print A;END

Examples• So let’s say we want to express the

following algorithm:– Read in a number and print it out double the

numberBEGINPROGRAM PrintDoubleNumber:Use variables: A,B OF TYPE Integer Read A; B = A*2; Print B;END

Examples• So let’s say we want to express the following algorithm to

print out the bigger of two numbers:– Read in two numbers, call them A and B. Is A is bigger

than B, print out A, otherwise print out B.

BEGINPROGRAM PrintBiggerOfTwo:Use variables: A,B OF TYPE Integer Read A; Read B; IF (A>B) THEN Print A; ELSE Print B; ENDIF;END

Examples

• So let’s say we want to express the following algorithm to print out the bigger of three numbers:– Read in three numbers, call them A, B and C.

• If A is bigger than B, then if A is bigger than C, print out A, otherwise print out C.

• If B is bigger than A, then if B is bigger than C, print out B, otherwise print out C.

ExamplesBEGINPROGRAM BiggerOfThree:Use variables: A,B,C OF TYPE Integer Read A; Read B; Read C; IF (A>B) THEN IF (A>C) THEN Print A; ELSE Print C; END IF; ELSE IF (B>C) THEN Print B; ELSE Print C; END IF; END IF;END

Examples• So let’s say we want to express the following

algorithm:– Print out the numbers from 1 to 5

BEGINPROGRAM Print1to5:Use variables: A OF TYPE Integer A = 1; WHILE (A != 6) DO Print A; A = A + 1; ENDWHILE;END

Examples

BEGINPROGRAM ComputeSum:Use variables: number1, number2, sum

OF TYPE IntegerDISPLAY “Enter the numbers”ACCEPT number1, number2Sum:=number1 + number2DISPLAY “SUM”END

Examples

BEGINPROGRAM CategoryOfInsurance:Use variables: category OF TYPE character

insurance OF TYPE stringACCEPT categoryDO CASE of category

CASE category = UDISPLAY Insurance := “not available”

CASE category = ADISPLAY Insurance := “double”

CASE category = BDISPLAY Insurance := “normal”

CASE category = MDISPLAY Insurance := “medically dependent”

OTHERWISE DISPLAY “entry is invalid”ENDCASEEND

ExamplesBEGINPROGRAM NumberRange0-100:Use variables: number

OF TYPE IntegerREPEAT

DISPLAY “Enter a numberbetween 0and 100”

ACCEPT numberUNTIL number <0 or number >100END

ExamplesCreate a flowchart for inputting your employee’s name. If the first letter starts from A to J then display “ First Category” , if K to T then display “ Second Category” otherwise display Third Category

If student's grade is greater than or equal to 60Print "passed“ else Print "failed“

Set the counter to 0. If the counter is more than 10 then customer receives free value meal otherwise no free value meal.