This document discusses planning tools used in programming, focusing on pseudocode. It defines pseudocode as a way for programmers to develop program logic without worrying about syntax. The document then covers the six basic computer operations that can be represented in pseudocode: (1) receiving input, (2) outputting information, (3) performing arithmetic, (4) assigning values to variables, (5) comparing variables to select actions, and (6) repeating groups of actions. It provides examples and guidelines for writing effective pseudocode using keywords, indentation, and other conventions.
3. Pseudocode
• It Means:
• IMITATION or FALSE CODE
• It is an imitation of the computer instruction
• Using this programmer can concentrate on
developing logic without worrying about
syntax
• Easy to convert into programming language
4. Writing Pseudocode
Basic computer operations
There are six basic computer operations
1.computer can receive information
2.computer can put out information
3.computer can perform arithmetic
4.computer can assign a value to a variable or
memory location
5.computer can compare two variables and select
one of two alternate actions
6.computer can repeat a group of actions
5. 5
Six Basic Computer Operations
1 A computer can receive information
– When a computer is required to receive
information or input from a particular source,
whether it is a terminal, a disk or any other
device, the verbs Read and Get are used in
pseudocode
Read => Input from a record
Get => Input from keyboard
Example pseudocode
1.Read student name
2.Get system data
3.Read number1, number2
4.Get tax_code
6. 6
Six Basic Computer Operations
2 A computer can put out information
– When a computer is required to supply
information or output to a device, the verbs
Print, Write, Put, Output, or Display are used
in pseudocode
– Print => send output to printer
– Write => send out to file
– Put, Output, Display => send
to screen
Example pseudocode
1.Print ‘Program Completed’
2.Write customer record to master file
3.Output total tax
4.Display ‘End of data’
7. 7
Six Basic Computer Operations
3 A computer can perform arithmetic
– Most programs require the computer to perform some sort of
mathematical calculation, or formula, and for these, a
programmer may use either actual mathematical symbols or the
words for those symbols
– To be consistent with high-level programming languages, the
following symbols can be written in pseudocode:
+ for Add - for Subtract
* for Multiply / for Divide ( ) for Parentheses
– When writing mathematical calculations for the computer,
standard mathematical ‘order of operations’ applies to
pseudocode and most computer languages
8. 8
Six Basic Computer Operations
4 A computer can assign a value to a variable or
memory location
– There are three cases where you may write pseudocode
to assign a value to a variable or memory location:
1. To give data an initial value in pseudocode, the verbs
Initialize or Set are used
2. To assign a value as a result of some processing the symbols
‘=‘ or ‘←’ are written
3. To keep a variable for later use, the verbs Save or Store are
used
9. 9
Six Basic Computer Operations
4 A computer can assign a value to a variable
or memory location
Example pseudocode
1.Initialize total_price to zero
2.Set student_count to zero
3.Total_price = cost_price + sales_tax
4.Total_price cost_price + sales_tax
5.Store customer_num in last_customer_num
10. 10
Six Basic Computer Operations
5 A computer can compare two variables and
select one or two alternate actions
– An important computer operation available to the
programmer is the ability to compare two
variables and then, as a result of the comparison,
select one of two alternate actions
– To represent this operation in pseudocode, special
keywords are used: IF and ELSE
12. 12
Six Basic Computer Operations
6 A computer can repeat a group of actions
– When there is a sequence of processing steps that need to be
repeated, a special keyword, WHILE is used in pseudocode
– The condition for the repetition of a group of actions is
established in the WHILE clause, and the actions to be
repeated are listed beneath it
13. Repetition using WHILE
Start
count = 0
count
<10
add 1 to
count
write count
Write
“The End”
Stop
1. count = 0
2. WHILE count < 10
2.1 ADD 1 to count
2.2 WRITE count
3. WRITE “The End”
Mainline
1.count = 0
2.DOWHILE count < 10
2.1 DO Process
3.WRITE “The End”
Process
2.1 ADD 1 to count
2.2 WRITE count
Modular
14. Rules for Pseudocode
• Write only one statement per line
• Capitalize initial keyword
• Indent to show hierarchy
• End multiline structures
• Keep statements language
independent
15. One Statement Per Line
Each statement in pseudocode should
express just one action for the computer.
Pseudocode
READ name, hoursWorked, payRate
gross = hoursWorked * payRate
WRITE name, hoursWorked, gross
16. Capitalize Initial Keyword
In the example below note the words: READ and
WRITE. These are just a few of the keywords to use,
others include:
READ, WRITE, IF, ELSE, ENDIF, WHILE, ENDWHILE
Pseudocode
READ name, hoursWorked, payRate
gross = hoursWorked * payRate
WRITE name, hoursWorked, gross
17. Rules for Variable Names
• Begin with lowercase letter
• Contain no spaces
• Additional words begin with capital
• Unique names within code
• Consistent use of names
18. Indent to Show Hierarchy
• Sequence:
Keep statements in sequence all starting in the same column
• Selection:
Indent statements that fall inside selection structure, but not the keywords that form
the selection
• Loop:
Indent statements that fall inside the loop but not keywords that form the loop
Each design structure uses a particular
indentation pattern
READ name, grossPay, taxes
IF taxes > 0
net = grossPay – taxes
ELSE
net = grossPay
ENDIF
WRITE name, net
19. End Multiline Structures
See the IF/ELSE/ENDIF as constructed
above, the ENDIF is in line with the IF.
The same applies for WHILE/ENDWHILE
etc…
READ name, grossPay, taxes
IF taxes > 0
net = grossPay – taxes
ELSE
net = grossPay
ENDIF
WRITE name, net
22. The Selection Structure
amount < 100
interestRate = .06 interestRate = .10
yes no
IF amount < 100
interestRate = .06
ELSE
Interest Rate = .10
ENDIF
Pseudocode
23. The Looping Structure
In flowcharting one of the more confusing
things is to separate selection from looping.
This is because each structure use the
diamond as their control symbol. In
pseudocode we avoid this by using specific
keywords to designate looping
WHILE/ENDWHILE
REPEAT/UNTIL
24. WHILE / ENDWHILE
Start
count = 0
count
<10
add 1 to
count
write count
Write
“The End”
Stop
count = 0
WHILE count < 10
ADD 1 to count
WRITE count
ENDWHILE
WRITE “The End”
Mainline
count = 0
WHILE count < 10
DO Process
ENDWHILE
WRITE “The End”
Process
ADD 1 to count
WRITE count
Modular
25. REPEAT / UNTIL
Start
count = 0
count
<10
add 1 to
count
write count
Write
“The End”
Stop
count = 0
REPEAT
ADD 1 to count
WRITE count
UNTIL count >= 10
WRITE “The End”
Mainline
count = 0
REPEAT
DO Process
UNTIL count >= 10
WRITE “The End”
Process
ADD 1 to count
WRITE count
Modular
26. Advantages & Disadvantages
Flowchart Advantages:
Standardized
Visual
Pseudocode Advantages
Easily modified
Implements structured
concepts
Done easily on Word
Processor
Flowchart Disadvantages:
Hard to modify
Structured design elements not
implemented
Special software required
Time Consuming
Pseudocode Disadvantages:
Not visual
No accepted standard, varies from
company to company
27. Working with Fields
Calculations
+ add
- subtract
* multiply
/ divide
** or ^ exponentiation
( ) grouping
Selection
> greater than
< less than
= equal to
>= greater than or
equal to
<= less than or equal to
!= not equal to