c++ computer programming language datatypes ,operators,Lecture 03 04
- 2. 2 • Problem solving • Six steps towards problem solution • Basic problem solving concepts • Data types • Data literals • Variables • Constants • Rules for naming variable and constant • Operators
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- 4. 4 • In every day life people make decisions to solve many problems. • The problems may be unimportant as what to watch on TV or as important as choosing a new profession. • If a bad decision is made, time and resources are wasted. • So it is important that people know how to make decisions well.
- 5. 5 • There are six steps to follow to ensure the best decision: Evaluate the solution List instruction to solve problem Selectthe best solution Identify alternative solutions Understand the problem Identify the problem
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- 7. 7 • The first step towards solving a problem is to identify the problem. • If you don’t know what the problem is, you cannot solve it. • In a classroom situation, most problems have been identified for you and given to you in the form of written assignments or problems out of a book. However, when you are doing problem solving outside the classroom, you need to make sure you identify the problem before you start solving it.
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- 9. 9 • You must understand what is involved in the problem before you can continue toward the solution. • You cannot solve a problem if you do not know the subject. • For example, to solve a problem involving average of numbers, you must know how to calculate average; to solve a problem of trigonometry, you must know trigonometry.
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- 11. 11 • A single problem can be solved in many different ways. • Identify and list all the possible solutions to the problem. • For example there are multiple ways to sort the numbers as: • Insertion sort • Selectionsort • Bubble sort
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- 13. 13 • Analyze and identify the pros and cons of every alternative solution. • Choose the solution that is optimal and best matches with your requirements. • For example out of all the sorting options you choose bubble sort as your best solution.
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- 15. 15 • Write down general step by step procedure to solve the problem. • For example to solve problem of calculating average of three numbers: • Step 01 : Ask numbers a, b, and c from the user • Step 02 : Add a, b, c and store result insum • Step 03 : Divide sum by 3 and store result in avg • Step 04 : Display avg
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- 17. 17 • Finally evaluate and test the solution, means to check its result to see if it is correct and satisfies the needs. • For example, when a person needs a pen to write a letter, buying him marker may be a correct solution, but it may not be very satisfactory. • If the result is either incorrect or unsatisfactory, then the problem solver must review the list of instructions to see that they are correct or start the process all over again.
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- 20. • Every problem involves some sort of data in it. • The data can be: • Numbers • Integers (e.g. 24, 5874, -547) • Floating (e.g. 45.214, 0.2547, -658.748) • Characters (e.g. ‘a’, ‘f’, ‘#’, ‘?’, ‘!’, ‘w’) • String (e.g. “mehran”, “computer”, “MUET CSE”) • Logical (e.g. True and False, Yes and No, 0 and 1) • The type of data is known as data type of that data item. 20
- 21. Data Item Example Value Data Type Age of a person 35 Integer Current year 2014 Integer Radius of circle 27.58 Floating Value of PI 3.14159 Floating A vowel e Character A key on keyboard ? Character Person’s name Ahmed Ali String Address of an office Department of CSE-MUET String Is 1st number greater than 2nd? True or T or Yes or 1 Logical Is 7 less than 5 ? False or F or No or 0 Logical 21
- 22. Data Types Data Item Example Value Data Type Number of students Brand name of smartphone Is 5 an even number? Count of cars in parking Speed of a car Your grade in result Is 13 a prime number ? Title of book chapter Percentage of marks Option in MCQ 22
- 23. • A fixed value that any data type can take is called as literal. • A number literal is always written without quotes. (15, 68, 25.14, 578.14) • A character literal is always written in single quotes. (‘a’, ‘f’, ‘#’, ‘?’, ‘!’) • An string literal is always written in double quotes. (“mehran”, “computer”) • An logical literal is always written without quotes. (True, False, T,F,Yes, No, 1, 0) 23
- 24. Data Literal Type of Literal “Ali” String ‘b’ Character 25.2 Floating “87.5” String ‘4’ Character 4 Integer 4.0 Floating “true” String false Logical “mehran” String 24
- 25. • In programming, a variable is the memory (RAM) location that can store the data temporary. • Every program uses some sort of data and each data item is stored temporarily in the variables. • Every variable has: • Name • Data type • Value 25
- 26. • Consider two of the examples. • In first example, we have a variable whose name is radius, its data types is floating and its value is 25.5. • In second example, we have a variable whose name is option, its data type is character and its value is b. • The name of the variable is called as the identifier. 25.5 radius b option 26
- 27. • The data type of the variable defines that what type of the data will be stored in a variable. • Once the data type of variable is defined, it cannot hold any value of other data type. • The value of the variable is changeable but its data type is not. 27
- 28. • In programming, a constant is a variable whose value remains fixed through out the program. • In certain programs some sort of data remains unchangeable through out the program, hence we use constants to stored that data so that it can not be altered. 28
- 29. • Consider three of the examples. • In first example, we have a constant whose name is PI, its data types is floating and its value is 3.141. • In second example, we have a constant whose name is E (Euler’s number), its data type is floating and its value is 2.718. 3.141 PI 2.718 E 29
- 30. • In third example, we have a constant whose name is SPEEDOFLIGHT, its data types is floating and its value is 3 x 108. 3E8 SPEEDOFLIGHT 30
- 31. • The name of any variable for constant is called as identifier. • There are certain rules to follow when setting the identifier. • Rule 1: May contain letters (A-Z, a-z), digits (0-9) or an underscore sign. • Rule 2: It must start with letter or underscore sign. • Rule 3: Should not contain any space in between. • Rule 4: Should not be like any keyword of language like, int, cout, float. • Rule 5: It is case sensitive i.e. radius is not same as Radius or RADIUS. 31
- 32. • Rule 6: Must be unique i.e. no any two variables have same identifier. • Rule 7: Must be relevant i.e. var1 is inappropriate identifier to store the area of circle, use area of area_circle instead. • Rule 8: The identifier for constant is written with all capital letters. i.e. PI, SPEEDOFLIGHT, E etc. 32
- 33. Identifier Valid/Invalid Remarks first_number Valid first number Invalid Must not contain space in between number_1 Valid 1st_number Invalid Must start with a letter or underscore sign first# Invalid Must not contain invalid character $ int Invalid Must not be like keyword firstNumber Valid int_first_number Valid first_number_$ Invalid Must not contain invalid character # 1st_# Invalid Must start with a letter or underscore sign Must not contain invalid character # 33
- 34. Rules for naming Variables and Constants Identifier Valid/Invalid Remarks number of items #_of_items price/item number_items itemCount item#Price itemPrice_1 5_itemPrice ITEM_PRICE $_per_item 34
- 35. • Computer performs several operations on the data. The operations are represented by symbols known as operators. • Operands are the data on which the operation is performed. • Operand may be constant or stored in one of the variable. 35
- 36. • Example 1: a + b • + is the operator • a and b are the operands • Both a and b are variables • Example 1: 2 * length • * is the operator • 2 and length are the operands • 2 is constant and length is avariable 36
- 37. Operator Symbol Example Operation Resultant Addition + 10 + 26 36 Subtraction - 10 - 8 2 Multiplication * 4 * 20 80 Division / 25/5 5 Remainder/Modulus % 13 % 5 3 Power ^ 2^4 16 37
- 38. Operator Symbol Example Operation Resultant Greater Than > 5 > 6 false Less Than < 10 < 15 true Greater Than or Equals To >= 41 >= 90 true Less Than or Equals To <= 16 <=16 true Equals To == 15 == 19 false Not Equals To != 14 != 80 true 38
- 39. Operator Symbol Example Operation Resultant AND & true & true true true & false false false & true false false & false false OR ¦ true ¦ true true true ¦ false true false ¦ true true false ¦ false false NOT ! ! true false ! false true 39
- 40. A B A & B True True True True False False False True False False False False 40
- 41. A B A ¦ B True True True True False True False True True False False False 41
- 42. A ! A True False False True 42