Lesson 2 McManus COP1006 1

 Computational ◦ problems involving some kind of mathematical processing  Logical ◦ Problems involving relational or logical processing  Repetitive ◦ Problems involving repeating a set of mathematical and/or logical instructions. McManusCOP10062

 The building blocks of equations and expressions ◦ Constants ◦ Variables ◦ Operators ◦ Functions McManusCOP10063

 A value ◦ a specific alphabetical and/or numeric value ◦ Does not change during the processing of all the instructions in a solution  Can be of any data type ◦ Numeric, alphabetical or special symbols  Examples ◦ 3, 5, 10, “Mulder”, “Scully”, “+”, “-”, “/” ◦ Note: “” indicates datum rather than variable name McManusCOP10064

 In some programming languages, constants can be named ◦ Provides protection to the constant value and other areas of the program. ◦ Cannot be changed once given initial value  Example ◦ SalesTaxRate = 6 ◦ Commission_Rate = 6 ◦ Note: no spaces within variable names McManusCOP10065

 May change during processing  A name is assigned to each variable used in a solution. ◦ The name references the memory area where the value is stored.  May be of any data type  Examples ◦ Age, LastName, Address, PayRate McManusCOP10066

 Use mnemonic terms, that is, the name means something ◦ Use PayRate not Z  Do not use spaces ◦ Either combine terms (PayRate) or include an underscore to separate (Pay_Rate)  Do not use special symbols  Be consistent! ◦ Some languages are case sensitive ◦ PayRate, Pay_Rate, PAYRATE, or PAY_RATE  Use appropriate naming convention McManusCOP10067

 Data ◦ Raw, organized facts  Information ◦ Meaningful output McManusCOP10068

 Most common types ◦ Numeric ◦ Character ◦ Logical  Most languages include other data types ◦ Date ◦ Currency ◦ User-defined McManusCOP10069

Data TypeData SetExamples IntegerAll whole numbers RealAll real numbers (whole + decimal) Character (uses quotation marks) All letters, numbers, and special symbols “A”, “a”, “1”, “5”, “+”, “%” String (uses quotation marks) Combinations of more than one character “Mulder” “Scully” “ ” LogicalTrue or FalseTrue False McManusCOP100610

 Include all types of numbers ◦ Integers  3, 5, -5, 0, -1 and 32,767 ◦ Real numbers (floating point numbers)  ,  Scientific Notation  2.3E5 or 5.4E-3, where E stands for the Power of 10 ◦ Can be Positive or Negative McManusCOP100611

 Alphanumeric data set ◦ Consists of  all single-digit numbers,  letters, and  special characters available to the computer ◦ contained within quotation marks McManusCOP100612

 EBCDIC – Extended Binary Coded Decimal Information Code ◦ Used on IBM mainframes  ASCII - American Standard Code for Information Interchange ◦ 256 characters(1 byte)  First 128 – standard  Second 128 – specific to computer  Unicode(2 bytes) ◦ Replacing ASCII as standard on PC’s McManusCOP See Appendix C

 Made up of one or more characters.  Contained within quotation marks  Cannot be used within calculations McManusCOP100614

 “123” is not the same thing as 123 ◦ The first one is a string ◦ The second one is a number  Becomes important when deciding when a piece of data is a string or a number ◦ Ex. Social Security Numbers  The first one contains 11 characters and is left aligned whereas the second contains 9 numbers and is right aligned McManusCOP100615

 The computer’s particular coding scheme (ASCII, Unicode, or EBCDIC) converts the character to its associated ordinal number ◦ Note: Uppercase letters have a smaller ordinal values than lowercase letters  “A” = 193 whereas “a” = 129 (Unicode 16-bit)  “A” = 65 whereas “a” = 97 (ASCII 8-bit)  Once converted, each character, one at a time, can be compared McManusCOP100616

 Joins character data or string data together  Operators: + and & ◦ Dependent on programming language ◦ & can mix data types ◦ + cannot mix data types (also known as Join)  Examples ◦ FName & “ ” & MI & “ ” & LName ◦ “James” + “ ” + “T.” + “ ” + “Kirk” = “James T. Kirk” ◦ “James” & “ ” & “T.” & “ ” & “Kirk” = “James T. Kirk”  Note the space at the end of the T. McManusCOP100617

 Consists just two pieces of data ◦ True and False ◦ Different programming languages also allow  Yes and No  1 (True) and 0 (False)  On and Off McManusCOP100618

 Dependent on programming language, numerous other pre-defined data types are available. ◦ Examples  Dates01/01/1900 January 1, 1900  Times03:35:05 PM15:35:05  Currency ◦ Note: This is how the data will be stored, not how it is formatted. McManusCOP100619

 User-defined Data types ◦ Defined by the user as a new data type  Examples  Records Employee_Record Fname Lname SSN End McManusCOP100620

 Programmer designates the data type  Data types cannot be mixed ◦ Called data typing  All data to be used in calculations must be declared as a numeric data type  Each data type uses a data set or domain ◦ Integers – typically > 0 -> but is programming language dependent ◦ Characters – all alphanumeric characters included in the computer’s coding scheme ◦ Logical – the words “true” and “false” McManusCOP100621

 Small sets of instructions that perform specific tasks and return values.  Two types: ◦ Pre-defined  Built into a computer language or application. ◦ User-defined McManusCOP100622

 Benefits ◦ Reduces the amount of code that needs to be written, thus reducing errors of repetition ◦ Shortens the development time ◦ Improves readability McManusCOP100623

 Data usually placed within parentheses that the function uses without altering the data ◦ In Sqrt(n), the n represents the parameter, in this case a number ◦ In Value(s), the s represents a string McManusCOP100624

 Mathematical  String  Conversion  Statistical  Utility  Specific to each programming language…a partial list follows McManusCOP100625

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McManusCOP Error is a special function that appears in most languages and upon execution return control to the program when (not if) system errors occur.

 The data connectors within expressions and equations.  Two types of operations ◦ Unary  Negation ◦ Binary  Addition, Subtraction, Multiplication, Floating Point Division and Integer Division McManusCOP100631

 Mathematical ◦ +, -, *, / ◦ \, Mod ◦ ^, and ◦ functions  Relational ◦, =, =, <>  Logical ◦ And, Or, Not, XOR, EQV McManusCOP100632

 Integer Division (\) ◦ Regular Floating Point Division, except only the whole number part of the answer is returned. ◦ If given a Floating Point number, the number is rounded—first—before division occurs.  Modulo Division (Mod) or Modulus ◦ The remainder part of the answer is returned. McManusCOP100633

 Returns either the keywords True or False or  Returns a non-zero or zero value. ◦ -9, -1, 1, 2 are equivalent to True ◦ 0 is equivalent to False  Is stored in two bytes McManusCOP100634

 Perform comparisons  variable - relational operator - variable ◦ Ex. If Y > Z then... ◦ = equal ◦ <> not equal ◦ < less than ◦ > greater than ◦ <= less than or equal to ◦ >= greater than or equal to McManusCOP100635

 And, Or, XOR, Not, EQV  Boolean Expressions are used ◦ To create more complicated Boolean Expressions. ◦ If a = b AND c < d Then …  They are defined by using Truth Tables… ◦ Know the significance of each! McManusCOP100636

 Significance: The only time the result is True is if both A and B are True. McManusCOP100637

 Significance: The only time the result is False is if both A and B are False. McManusCOP100638

 Also called the “logical complement” or “logical negation”  Significance: Whatever the value of A is, NOT A will be the opposite. McManusCOP100639

 Significance: The only time the result is True is if A and B are different and False if both A and B are the same. McManusCOP100640

 Significance: The only time the result is True is if A and B are the same and False if both A and B are the different. McManusCOP100641

 Data and Operators are combined to form expressions and equations  To evaluate these in the proper order, a hierarchy of operations, or Order of Precedence, is used. ◦ Note: Whenever you want to clarify an equation, use the parentheses! McManusCOP100642

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 Evaluate the following:  A = True, B = False, C = True, D = False A or B or C and D and A and B and (not C) or (not D)  To do this, we create what’s called an Evaluation Tree… McManusCOP100644

McManusCOP A or B or C and D and A and B and (not C) or (not D) False True False True

 Expressions ◦ Process the data and the operands, through the use of the operators ◦ Does not store the resultant (answer) ◦ Examples Price * SalesTaxRate (Hours – 40) * Wage * 1.5 Length * Width McManusCOP100646

 Same as an expression, except the equation stores the resultant (answer) in a memory location  “takes on the value of” not equals ◦ Examples SalesTax = Price * SalesTaxRate OvertimePay = (Hours – 40) * Wage * 1.5 Area = Length * Width ◦ SalesTax is the memory location where the answer will be stored  Often called Assignment Statements McManusCOP100647

 Destructive Read-In ◦ The value stored in the variable on the left-hand side of the equals sign is replaced by the result of the expression on the right-hand side.  Non-Destructive Read-In ◦ Values used on the right-hand side are protected from being changed. McManusCOP SalesTax = Price * SalesTaxRate D R-I ND R-I ND R-I

 Algebraic Expressions cannot be represented in the computer.  They must be converted to a form the computer will recognize.  Thus, Straight Line Form McManusCOP = (X – Y) / ( (X + Y)^2 / (X – Y )^2 ) straight line form

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