fundamental programming lect 3

Instructor : Muhammad Haris

All Rights Reserved to Department of Computer Science – GCU Lahore

Programming Fundamentals

Tasks (from previous lecture)

Calculate area of a rectanglearea = base height

Find Cube of a Number Calculate Marks Percentage

(marks obtained / total marks) 100

Calculate Sales Taxamount (tax percent / 100)

Find “no. of minutes” and “no. of seconds” for given “no of years”

Programming Fundamentals | Lecture-3 2

Power of Computer Programs Once given the input

They perform the instructions (or no. of steps as instructed by the programmer) themselves and give the desired output○ No matter how complex the problem is and

how long they have to work on it


Now We Will Further Explore Their Power

Consider this Problem

Find absolute value after subtracting one number from anotherDifference = number1 – number2


Difference of Two numbers


START

READ number1, number2

difference = number1 - number2

DISPLAY difference

STOP

Will result in a negative value if number1 is

smaller than number2

Is This Solution Correct?


START



DISPLAY difference

STOP

difference = difference * -1

Analyze the Problem

There exists two conditionsCondition-1

○ Difference is positiveCondition-2

○ Difference is negative


What is to be Done? There exists two conditions

Condition-1○ Difference is positive

Do not do any conversion, because value is already positive

Condition-2○ Difference is negative

Convert it into a positive value by multiplying it by “-1”


Should we design two different solutions?

9Programming Fundamentals | Lecture-1

What is Required?

Need to design a solution in such a way which can decide for itself whether to multiply the difference by “-1” or not (by checking the value of difference)

The graphical shapes which we have learned so far are insufficient to provide this kind of “decision making”


Decision Box


Decision Rule

YesNo

Always in the form whose answer is

“Yes” or “No”


START



DISPLAY difference

STOP

difference = difference * -1

difference < 0YesNo

Power of Computers

Decision MakingProgrammers can instruct computers to

make decisions while solving a problem○ As the complexity of problems increases,

decision making process become more extensive

This way computers prove very useful by performing laborious tasks of decision making


Another Example

Find smaller of two numbers Input

number1number2

Outputsmaller

ProcessingCompare the numbers with each other and

decide which one is smaller



START


DISPLAY smaller

STOP

smaller = number1

number1 < number2YesNo

smaller = number2

Alternative


START


STOP

DISPLAY number1

number1 < number2YesNo

DISPLAY number2

Comparison Operators

< (less than) > (greater than) <= (less than equal to) >= (greater than equal to) == (equal to) != (not equal to)


Output a Message


DISPLAY “This is a message”

Try it Yourself

Find whether a number is negative or not?

Find whether two numbers are equal or not?

Multiply two numbers if their difference is greater than 0


Some Keywords

Look for these keywords in problem statement in order to determine the usage of decision boxIfIf and only ifWhether


Tasks (to be done by next lecture) Find whether the sum of two numbers is

greater than 50 Find whether the sum of two numbers is

greater than the third number? Divide a number by another if only if the

second number is not equal to “0” Determine whether a student is “passed” or

“failed” from his marksA student securing marks less than 50 is

considered “failed”



BE PREPAREDFOR QUIZ

IN NEXT LECTURE

fundamental programming lect 3

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