Unit-8 Programming

Programming
Concepts in
Pseudocode
DECLARE Statement
• It is the way of introducing a variable
to the program/pseudocode.
DECLARE A: INTEGER
DECLARE B: REAL
COMMENTS in pseudocode
• It is used to label and documenting the
lines in pseudocode.
• It is represented by ‘//’ symbol.

// Pseudocode to add two numbers

DECLARE A: INTEGER
DECLARE B: INTEGER
DECLARE C: INTEGER
C A+B
VARIABLE
• It is a name given to a container
carrying a value(String, integer, Real,
Boolean, Char etc.) to which helps in
developing a program.
• The value of the variable can be
changed during the execution of the
program.
A 10 # 10 is assigned to variable
A
CONSTANT in Pseudocode
• It is a container which stores the
value permanently without being
changed during the exceution of
program.
Example:
• CONSTANT PI : 3.14
OUTPUT statement
• It is used to print the result from the
pseudocode in the form of integer
value, real value, string value etc.
onto the screen..
Example:
OUTPUT “Good Morning”
INPUT statement
• It is used to accept data from the
user into the pseudocode through the
keyboard.
Example:
OUTPUT “Enter the age of the person”
INPUT Age
BASIC DATA TYPES
1.Integer: It represents a whole
number value e.g: 10,20 etc.
2.Real: It represents a decimal
(floating) value e.g: 5.2, 9.6 etc
3.Char: It represents a single alphabet
value e.g: ‘a’, ‘b’, etc.
4.String: It stores the collection of
alphabets e.g: ‘ royal’ etc.
5.Boolean: It stores the value either
TRUE or FALSE.
Why do we need data types?
• In order for a computer system to
process and store data
effectively
• data to be stored in an
appropriate way,
• data to be manipulated
effectively,
• automatic validation in some
cases.
Computer Programming
Languages
• Machine language: Based on binary
number(0,1).
• Assembly language: Based on
symbols & hardware related english
words.
• High level language: It is based on
english words to develop a program. It
is easy to use and learn.
• e.g: PYTHON, JAVA, VISUAL BASIC etc.
 # Pseudocode to find volume
of a cylinder
DECLARE Radius: INTEGER
DECLARE Height: REAL
DECLARE Vol: REAL
CONSTANT PI: 3.142
INPUT “Enter the radius”, Radius
INPUT “Enter the height”, Height
Vol (PI * Radius * Radius * Height)
OUTPUT” The volume of cylinder is ”, Vol
# Python program to find
volume of cylinder
CONSTANT PI = 3.142
Radius = float(input("Please enter the
radius of the cylinder "))
Length = float(input("Please enter the
length of the cylinder "))
Volume = Radius * Radius * Length * PI
print("Volume of the cylinder is ",
Volume)
Flow of Control
1. Sequence
2. Selection / Conditional
statements
3. Iteration / Loop /Repetitive
construct
Sequence
• An algorithm contains instructions that are
carried out one after another, and the
sequence determines the order that these
instructions are carried out. For example, a
basic algorithm for making a cup of tea
might look like this:
• 1. Boil the kettle.
• 2. Put a teabag in a mug.
• 3. Pour water into the mug.
• 4. Add sugar and milk.
• 5. Stir.
• 6. Drink the tea.
• #Pseudocode to find Volume of a
cuboid
• DECLARE L : INTEGER
• DECLARE B : REAL
• DECLARE H : INTEGER
• DECLARE Volume: REAL
• Volume (L * B * H)
• OUTPUT ”The volume of cuboid is :”,
Volume
Selection/ Conditional
statement
• Selection is a very useful technique,
allowing different routes through the
steps of a program

• Selection was demonstrated in

pseudocode with the use of IF and
CASE statements
IF…THEN…ELSE…ENDIF
It is the conditional statement to select
between two flow of control.

Example:

IF Age > 17
THEN
OUTPUT "You are an adult“
ELSE
OUTPUT "You are a Child“
ENDIF
CASE…OF…OTHERWISE…
ENDCASE
• Case statements are used when there are multiple
choices to be made or select from.
• Example:
• CASE OF OpValue
• "+" : Answer¨Number1 + Number2
• "-" : Answer¨Number1 - Number2
• "*" : Answer¨Number1 * Number2
• "/" : Answer¨Number1 / Number2
• OTHERWISE OUTPUT "Please enter a
valid choice“
• ENDCASE
Iteration/Loops
• When some actions performed as part of
an algorithm need repeating this is called
iteration. Loop structures are used to
perform the iteration.
• Types of loops
1. Count-controlled loops (for a set number
of repetitions)
2. Pre-condition loops – condition given at
the beginning & may have no iterations
3. Post-condition loops – condition given at
the end & always has at least one
iteration
TYPES OF LOOPS
• FOR…TO…NEXT
• WHILE … DO …ENDWHILE
• REPEAT … UNTIL
String Handling
• Strings are used to store text.
• Every string contains a number of
characters, from an empty string,
which has no characters stored, to a
maximum number specified by the
programming language.
• The characters in a string can be
labelled by position number starting
with either 0 or 1.
String Library Methods
• LENGTH(): It is used to count the characters
in a string
Example: LENGTH(“Python”)
Output will be 6

• SUBSTRING(): It is used to extract the part

of a string.
Example: SUBSTRING(“Computer
Science”,10,7)
Output will be Science
• UCASE(): It converts a string in uppercase.
Example:
UCASE(Computer)
Output will be COMPUTER

• LCASE(): It converts a string in lowercase.

Example:
LCASE(Computer)
Output will be computer
• ISUPPERCASE(): It checks whether
a string is in uppercase or not.
Example:
ISUPPERCASE(Computer)
Output will be False

• ISLOWERCASE(): It checks
whether a string is in lowercase or
not.
Example:
ISLOWERCASE(computer)
Output will be True
Arithmetic Operators
Logic Operators

All programming languages make use of

logical operators to decide which path to take
through a program.
Boolean operators
• All programming languages make use
of Boolean operators to decide
whether an expression is true or
false.
• # Pseudocode to find average marks
of FIVE subjects of a student.
• DECLARE Marks : INTEGER
• DECLARE Total: INTEGER
• DECLARE Average : REAL
• FOR I 1 TO 5
• INPUT “Enter the marks”, Marks
• Total Total+ Marks
• NEXT I
• Average Total/5
• OUTPUT” The Average marks is”,
Average
• # Pseudocode to find average marks of five
subjects of ten students.
• DECLARE Marks : INTEGER
• DECLARE Total: INTEGER
• DECLARE Average : REAL
• FOR I 1 TO 10 # no. of students
• FOR J 1 TO 5 # no. of subjects
• INPUT “Enter the marks”, Marks
• Total Total+ Marks
• NEXT J
• Average Total/5
• OUTPUT ”The Average marks of student”, I,
Average
• Average 0
• Total 0
NEXT I
Use of nested statements
• Selection and iteration statements
can be nested one inside the other.
This powerful method reduces the
amount of code that needs to be
written and makes it simpler for a
programmer to test their programs.

• One type of construct can be nested

within another – for example,
selection can be nested within a
SUBROUTINES(Procedures
and functions)
• When writing an algorithm, there are
often similar tasks to perform that make
use of the same groups of statements.
• Instead of repeating these statements
and writing new code every time they
are required, many programming
languages make use of subroutines,
also known as named procedures or
functions.
PROCEDURE
• A procedure is a set of programming
statements grouped together under a
single name that can be called to
perform a task at any point in a
program.
• It would not return any value to the
main program.
FUNCTION
• A function is a set of programming
statements grouped together under a
single name that can be called to
perform a task at any point in a
program.
• In contrast to a procedure, a function
will return a value back to the main
program.
PARAMETERS
• Parameters are the variables that
store the values of the arguments
passed to a procedure or function.
Some but not all procedures and
functions will have parameters.
Syntax of PROCEDURE(without
parameters)

Procedure will be called by CALL

statement
Syntax of PROCEDURE(with
parameters)
FUNCTIONS
• A function is just like a procedure except
it always returns a value. Just like a
procedure it is defined once and can be
called many times within a program.
• Unlike procedures, function calls are not
standalone and instead can be made on
the right-hand side of an expression.
• The keyword RETURN is used as one of
the statements in a function to specify
the value to be returned. This is usually
the last statement in the function
definition.
Syntax of FUNCTION(with
parameter)
• Because a function returns a value, it
can be called by assigning the return
value directly into a variable as
follows:

NOTE: Procedure calls are single

standalone statements. Function calls
are made as part of an expression, on
the right-hand side.
LOCAL VARIABLE
• A local variable can only be used by
the part of the program it has been
declared in – its scope is restricted to
that part of the program.
• It is defined in a FUNCTION or
PROCEDURE.
GLOBAL VARIABLE
• A global variable can be used by
any part of a program – its scope
covers the whole program.
Library routines
• The Funtions that are ready to be
incorporated into a program. These
routines are fully tested and ready for use.
• A programming language IDE usually
includes a standard library of functions
and procedures.
• These standard library routines perform
many types of task – such as the string
handling functions like SUBSTRING(),
LENGTH() etc.
• MOD – returns remainder of a
division
• DIV – returns the quotient (i.e. the
whole number part) of a division
• ROUND – returns a value rounded to
a given number of decimal places
• RANDOM – returns a random
number.
Here are some examples of these library
routines
• in pseudocode:
• Value1 MOD(10,3) returns the
remainder of10 divided by3
• Value2 DIV(10,3) returns the
quotient of10 divided by3
• Value3 ROUND(6.97354, 2) returns
the value rounded to2 decimal places
• Value4 RANDOM() returns a random
number between 0 and1 inclusive
• Value5 DIVMOD() returns both
answers,the first answer is DIV and the
second answer is MOD
Creating a maintainable program
A maintainable program should:
1. Always use meaningful identifier names
for variables, constants, arrays,
procedures, functions.
2. be divided into modules for each task
using:
– procedures
– functions
3. be fully commented using your
programming language’s commenting
feature.
•
Array
• An array is a data structure
containing several elements of the
same data type.
• These elements can be accessed
using the same identifier(array)
name.
• The position of each element in an
array is identified using the array’s
index(location)
One dimensional array
• A one-dimensional
array can be
referred to as a list.

Here is an example
of a list with 10
elements in it where
the first element has
an index of zero.
• When a one-dimensional array is
declared in
pseudocode( Declaration)
• the name of the array
• the first index value
• the last index value
• and the data type
How to declare a new array called MyList ?

Adding the number 27 to the fourth position in

the array MyList as follows:
How to input an ONE-DIMENSIONAL
array from the user?
How to input an TWO-
DIMENSIONAL array from the user?
File Handling
• Data stored in a file can thus be
accessed by the same program at a
later date or accessed by another
program.
• Computer programs store data that
will be required again in a file
Why do we need a file?
• While any data stored in RAM will be
lost when the computer is switched
off, when data is saved to a file it is
stored permanently.
WRITING INTO A FILE
udocode to write a text input by the user into
named “Mytext.txt”
READING FROM A FILE
Pseudocode to read the text from the file
named “Mytext.txt” and print it onto the
screen.