Pseudocode Skill 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.

Pseudocode Sequence

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: 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 and/or sugar; Serve; END.

Pseudocode SeLECTION

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.

Pseudocode ITERATION

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) STATEMENT or STATEMENT BLOCK concluded with ENDWHILE WHILE Loop REPEAT statement UNTIL (condition is true) REPEAT UNTIL Loop FOR (starting state, final state, increment) Statement ENDFOR 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 entry If this is the required entry Then write down phone number Else get next entry If this is the correct entry then write done entry else get next entry if this is the correct entry Consider the problem of searching for an entry in a phone book with only condition: Get first entry; Call this entry N; WHILE N is NOT the required entry DO Get next entry; ENDWHILE; We may rewrite this as follows:

Pseudocode (Iteration) BEGIN PROGRAM 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 Or as a program:

Pseudocode eXAMPLES

Examples So let’s say we want to express the following algorithm: Read in a number and print it out. BEGIN PROGRAM 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 number BEGIN PROGRAM PrintDoubleNumber: Use variables: A,B OF TYPE Integer Read A; B = A*2; Print B; END

Examples BEGIN PROGRAM PrintBiggerOfTwo: 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. BEGIN PROGRAM 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.

Examples BEGIN PROGRAM BiggerOfThree: Read A; Read B; Read C; 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; END

Examples So let’s say we want to express the following algorithm: Print out the numbers from 1 to 5 BEGIN PROGRAM Print1to5: Use variables: A OF TYPE Integer A = 1; WHILE (A != 6) DO Print A; A = A + 1; ENDWHILE; END

Examples BEGIN PROGRAM ComputeSum: Use variables: number1, number2, sum OF TYPE Integer DISPLAY “Enter the numbers” ACCEPT number1, number2 Sum:=number1 + number2 DISPLAY “SUM” END

Examples BEGIN PROGRAM CategoryOfInsurance: Use variables: category OF TYPE character insurance OF TYPE string ACCEPT category DO CASE of category CASE category = U DISPLAY Insurance := “not available” CASE category = A DISPLAY Insurance := “double” CASE category = B DISPLAY Insurance := “normal” CASE category = M DISPLAY Insurance := “medically dependent” OTHERWISE DISPLAY “entry is invalid” ENDCASE END

Examples BEGIN PROGRAM NumberRange0-100: Use variables: number OF TYPE Integer REPEAT DISPLAY “Enter a number between 0 and 100” ACCEPT number UNTIL number <0 or number >100 END

Examples Create 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 60 Print "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.