Published on March 15, 2014
Planning Tools • ALGORITHMS • FLOW CHARTS • PSEUDO CODE • DECISION TABLES
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
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 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 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 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 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 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 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
The Selection Structure amount < 100 interestRate = .06 interestRaate = .10 yes no 1. IF amount < 100 1.1 interestRate = .06 2. ELSE 2.1 Interest Rate = .10Pseudocode
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
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
Rules for Pseudocode • Write only one statement per line • Capitalize initial keyword • Indent to show hierarchy • End multiline structures • Keep statements language independent
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
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
Rules for Variable Names • Begin with lowercase letter • Contain no spaces • Additional words begin with capital • Unique names within code • Consistent use of names
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
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
Types of Logic Structure • Sequence • Selection • Iteration
Sequence • Performing instruction one after another
The Selection Structure amount < 100 interestRate = .06 interestRate = .10 yes no IF amount < 100 interestRate = .06 ELSE Interest Rate = .10 ENDIF Pseudocode
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
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
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
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
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
Page 1 of 4 - Pseudocode Tutorial: The Basics - posted in Other Programming Tutorials: Introduction:-Well a user here asked me to make a pseudocode ...
Pseudocode: An Introduction Flowcharts were the first design tool to be widely used, but unfortunately they do not very well reflect some of the concepts ...
Pseudocode is a compact and informal high-level description of a program using the conventions of a programming language, but intended more for humans.
Pseudocode An Introduction Rules for Pseudocode Write only one statement per line One Statement Per Line Each statement in pseudocode should express just ...
Page 1 of 16 Pseudo code Tutorial and Exercises – Teacher’s Version Pseudo-code is an informal way to express the design of a computer program or an ...
6 minute tutorial illustrating pseudocode basics.
Objectives: To introduce common words and keywords used when writing pseudocode. Six basic computer operations. To define the three basic control ...