pseudo code basics

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Information about pseudo code basics
Education

Published on March 15, 2014

Author: sabiksabz

Source: slideshare.net

Description

This will help you to learn the basics about pseudo code

PLANNING TOOLS

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

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