2 beginning problem solving concepts for the computer

Beginning Problem-Solving Concepts for the Computer Page 1 of 17

Data Structures and Algorithms

Constants andVariables

Constants@ a value, that is, a specific alphabetical and/or

numeric value, that never changes during theprocessing of all the instructions in a solution

@ can be any type of data - numeric, alphabetical,or special symbols

Variable

@ may change during processing

@ the computer sets up a specific memory locationto hold the value of each variable name found in aprogram

@ can be any data type, just as constant




Rules for Naming and Using Variables

@ Name a variable according to what it reperesents,that is, HOURS for hours worked, PAYRATE for rateof pay, and so on.

@ Do not use spaces in a variable name. If a space isneeded, use the underline character.

@ Do not use a dash (or any symbol that is used as amathematical operator) in a variable name. Thecomputer will recognize these symbols asmathematical operators, turn your variable intotwo or more variables, and treat your variable asa mathematical expression.



@ After you have introduced a variable name thatrepresents a specific data item, this exact variablename must be used in all places where the dataitem is used.

@ Be consistent when using upper- and lowercasecharacters.

Rules for Naming and Using Variables




Data Types

Data@ unorganized facts

Information

@ what is returned to the user as output, orprocessed data

DATAData

Processed intoInformation

REPORT

ChecksDepositsBk. Chgs.

Calaculatesthe balance Balance Sheet

Input Output



Data Types

Data Type Data Set ExamplesNumeric: Integer All whole numbers 3570 , -54

Numeric: RealAll real numbers (whole +

decimal) 3792.91, 474526.23CHARACTER (surrounded by

quotation marks)All letters, numbers, and

special symbols"A","a", "M", "1",

"88","&", "#"

STRING (surrounded by quotation marks)

Combinations of more than one character "waahhh", "876860"

LOGICAL TRUE FALSE TRUE FALSE



Data Types

Data Data Type

The price of an item: 12.50, 34.00 Numeric: real

An account number: "A8693" Character StringA quantity: 10,345 Numeric: integer

The name of a school: "STI" Character String

A credit check: TRUE, FALSE Logical

A date: 06/21/03 or "01/11/81 Date or Character String



Data Types

Rules for Data Types

@ The data that define the value of a variable or aconstant will most commonly be one of three datatypes: numeric, character (including characterstring), or logical.

@ The programmer designates the data type duringthe programming process. The computer thenassociates the variable name with the designateddata type.

@ Data types cannot be mixed.



@ Each of the data types uses what is called a dataset. The numeric data uses the set of all base 10numbers, the plus sign (+), and the negative sign(-); the character type uses the set of dataconsisting of the words TRUE and FALSE. The useof any data outside the data set results in an error.

@ Any numeric item that must be used in calculationsresulting in a numeric results must be designatedas numeric data type. All other numbers should bedesignated as character or character-string datatypes, even if data are all numbers.

Rules for Data Types

Data Types



Functions

@ small sets of instructions that performspecific tasks and return values

@ usually built into a computer language orapplication

@ used as parts of istructions in a solution

Classes of Functions:

a Mathematicala Stringa Conversiona Statisticala Utility



Functions

Mathematical

Example ResultSQRT(4) 2ABS (-3) 3

ROUND (5.678) 6INTEGER (5.789) 5

StringExample Result

MID(S, 3, 2) where S = "THOMAS" "OM"

LEFT (S,3) where S = "THOMAS" "THO"

RIGHT (S, 3) where S= "THOMAS" "MAS"

LENGTH(S) where S = "THOMAS" 6



Functions

ConversionExample Result

VALUE ("57") +57STRING (+57) "57"

Statistical Example ResultAVERAGE (1,2,3,4) 2.5

MAX (1,2,3,4) 4MIN (1,2,3,4) 1SUM (1,2,3,4) 10

Utility Example ResultDATE 6/22/03TIME 2:55:03



Operators

@ the data connectors within expressions andequations

@ tell the computer how to process the data

@ tell the computer what type of processing(mathematical,logical or whatever) needs to bedone

Types of Operator@ Mathematical - include addition, subtraction,

multiplication, division, integer division, modulodivision, powers, and functions

@ Relational - = , <, >, >=, <=, <>

@ Logical - AND, NOT, and OR



Operators

Operation Resultant3.0 + 5.2 8.27.5 - 4.0 3.58.0 * 5.0 409.0/4.0 2

9\4 29 MOD 4 1

3 ^ 2 9

Mathematical

Relational

Operation Resultant3 = 2 FALSE5>1 TRUE

5 = 1 FALSE7 <= 8 TRUE9>=12 FALSE10 < 2 TRUE8<>8 FALSE



Operators

A Not AT FF T

A B A AND BT T TT F FF T FF F F

A B A OR BT T TT F TF T TF F F

Logical



Operators

Hierarchy of Operations( ) Reorders the hierarchy; all operations arecompleted within the parentheses using the samehierarchy.

1. Functions

Mathematical:2. Power3. \, MOD4. *, /5. +, -

Relational:6. =, <, >, <=, >=, <>

Logical:7. NOT8. AND9. OR



Expressions andEquations

Expression@ processes data, the operands, through the use of

operators

@ example: LENGTH * WIDTH

Equation@ stores the resultant of an expression in a memory

location in the computer through the equal (=) sign

@ example: AREA = LENGTH * WIDTH

@ often called assignment statements because thevariable on the left-hand side of the equal sign isassigned the value of the expression on the right-hand side

@ the equal sign does not mean equals; instead itmeans replaced by or is assigned the value of

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2 beginning problem solving concepts for the computer