PseudoCode

Pseudocode is a way of writing code that does not rely on a particular syntax or programming

language. This means that pseudocode is the stuff you write out before you tackle a difficult

problem. If you are a beginner programmer, you have probably needed to write out the problem

in layman’s terms first to truly grasp it.

It is a detailed yet readable description of what a computer program or algorithm must do,

expressed in a formally-styled natural language rather than in a programming language.

Pseudocode is sometimes used as a detailed step in the process of developing a program.

It is possible to write programs that will convert a given pseudocode language into a given

programming language.

PseudoCode Components

Computation/Assignment

Compute var1 as the sum of x and y

Assign expression to var2

Increment counter1

Input/Output

Input: Get var1, var2, …

Output: Display var1, var2, …

Selection

Single-Selection IF

1. IF condition THEN (IF condition is true, then do subordinate statement 1, etc. If

condition is false, then skip statements)

1.1 statement 1

1.2 etc.

Double-Selection IF

2. IF condition THEN (IF condition is true, then do subordinate statement 1, etc. If

condition is false, then skip statements and execute statements under ELSE)

2.1 statement 1

2.2 etc.

3. ELSE (else if condition is not true, then do subordinate statement 2, etc.)

3.1 statement 2

3.2 statement 3

4. SWITCH expression TO

4.1 case 1: action1

4.2 case 2: action2

4.3 etc.

4.4 default: actionx

Repetition

5. WHILE condition (while condition is true, then do subordinate statements)

5.1 statement 1

5.2 etc.

DO - WHILE structure (like WHILE, but tests condition at the end of the loop. Thus,

statements in the structure will always be executed at least once.)

6. DO

6.1 statement 1

6.2 etc.

7. WHILE condition

FOR structure (a specialized version of WHILE for repeating execution of statements a

specific number of times)

8. FOR bounds on repetition

8.1 statement 1

8.2 etc.

Pseudocode Example

Express an algorithm to get two numbers from the user (dividend and divisor), testing to make

sure that the divisor number is not zero, and displaying their quotient using pseudocode

1. Declare variables: dividend, divisor, quotient

2. Prompt user to enter dividend and divisor

3. Get dividend and divisor

4. IF divisor is equal to zero, THEN

4.1. DO

4.1.1. Display error message, "divisor must be non-zero"

4.1.2. Prompt user to enter divisor

4.1.3. Get divisor

4.2. WHILE divisor is equal to zero

5. ENDIF

6. Display dividend and divisor

7. Calculate quotient as dividend/divisor

8. Display quotient

Practice Examples

1. Write pseudo code that reads two numbers and multiplies them together and print out their

product.

Read num1 , num2

Set multi to num1*num2

Write multi

2. Write pseudo code that tells a user that the number they entered is not a 5 or a 6.

Read isfive

If(isfive = 5 or isfive = 6)

Write "your number is a 5 or 6"

Else

Write "your number is not 5 or 6"

3. Write pseudo code that performs the following: Ask a user to enter a number. If the number is

between 0 and 10, write the word blue. If the number is between 10 and 20, write the word red.

if the number is between 20 and 30, write the word green. If it is any other number, write that it

is not a correct color option.

Write "Please enter a number"

Read colornum

If (colornum >0 and colornum <= 10)

Write blue

else If (colornum >0 and colornum <= 10)

Write blue

else If (colornum >0 and colornum <= 10)

Write blue

else

Write "not a correct color option"

4. Write pseudo code to print all multiples of 5 between 1 and 100 (including both 1 and 100).

Set x to 1

While(x < 20)

write x

x = x*5

5. Write pseudo code that will count all the even numbers up to a user defined stopping point.

Read count

Set x to 0;

While(x < count)

Set even to even + 2

x = x + 1

write even

6. Write pseudo code that will perform the following.

a) Read in 5 separate numbers.

b) Calculate the average of the five numbers.

c) Find the smallest (minimum) and largest (maximum) of the five entered numbers.

d) Write out the results found from steps b and c with a message describing what they

are:

Write "please enter 5 numbers"

Read n1,n2,n3,n4,n5

Write "The average is"

Set avg to (n1+n2+n3+n4+n5)/5

Write avg

If(n1 < n2)

Set max to n2

Else

Set max to n1

If(n3 > max)

Set max to n3

If(n4 > max)

Set max to n4

If(n5 > max)

Set max to n5

Write "The max is"

Write max

If(n1 > n2)

Set min to n2

Else

Set min to n1

If(n3 < min)

Set min to n3

If(n4 < min)

Set min to n4

If(n5 < min)

Set min to n5

Write "The min is"

Write min

Curriculum

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Pseudo Code Notes

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