2 beginning problem solving concepts for the computer
1. Data Structures and Algorithms
Constants and
Variables
Constants
@ a value, that is, a specific alphabetical and/or
numeric value, that never changes during the
processing 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 location
to hold the value of each variable name found in a
program
@ can be any data type, just as constant
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2. Data Structures and Algorithms
Constants and
Variables
Rules for Naming and Using Variables
@ Name a variable according to what it reperesents,
that is, HOURS for hours worked, PAYRATE for rate
of pay, and so on.
@ Do not use spaces in a variable name. If a space is
needed, use the underline character.
@ Do not use a dash (or any symbol that is used as a
mathematical operator) in a variable name. The
computer will recognize these symbols as
mathematical operators, turn your variable into
two or more variables, and treat your variable as
a mathematical expression.
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3. Data Structures and Algorithms
Constants and
Variables
Rules for Naming and Using Variables
@ After you have introduced a variable name that
represents a specific data item, this exact variable
name must be used in all places where the data
item is used.
@ Be consistent when using upper- and lowercase
characters.
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4. Data Structures and Algorithms
Data Types
Data
@ unorganized facts
Information
@ what is returned to the user as output, or
processed data
Input Data Output
DATA Processed into REPORT
Information
Checks
Calaculates
Deposits Balance Sheet
the balance
Bk. Chgs.
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5. Data Structures and Algorithms
Data Types
Data Type Data Set Examples
Numeric: Integer All whole numbers 3570 , -54
All real numbers (whole +
Numeric: Real decimal) 3792.91, 474526.23
CHARACTER
(surrounded by All letters, numbers, and "A","a", "M", "1",
quotation marks) special symbols "88","&", "#"
STRING (surrounded Combinations of more
by quotation marks) than one character "waahhh", "876860"
LOGICAL TRUE FALSE TRUE FALSE
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6. Data Structures and Algorithms
Data Types
Data Data Type
The price of an item: 12.50, 34.00 Numeric: real
An account number: "A8693" Character String
A 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
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7. Data Structures and Algorithms
Data Types
Rules for Data Types
@ The data that define the value of a variable or a
constant will most commonly be one of three data
types: numeric, character (including character
string), or logical.
@ The programmer designates the data type during
the programming process. The computer then
associates the variable name with the designated
data type.
@ Data types cannot be mixed.
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8. Data Structures and Algorithms
Data Types
Rules for Data Types
@ Each of the data types uses what is called a data
set. The numeric data uses the set of all base 10
numbers, the plus sign (+), and the negative sign
(-); the character type uses the set of data
consisting of the words TRUE and FALSE. The use
of any data outside the data set results in an error.
@ Any numeric item that must be used in calculations
resulting in a numeric results must be designated
as numeric data type. All other numbers should be
designated as character or character-string data
types, even if data are all numbers.
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9. Data Structures and Algorithms
Functions
@ small sets of instructions that perform
specific tasks and return values
@ usually built into a computer language or
application
@ used as parts of istructions in a solution
Classes of Functions:
a Mathematical
a String
a Conversion
a Statistical
a Utility
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10. Data Structures and Algorithms
Functions
Example Result
SQRT(4) 2
Mathematical ABS (-3) 3
ROUND (5.678) 6
INTEGER (5.789) 5
Example Result
String 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
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11. Data Structures and Algorithms
Functions
Example Result
Conversion VALUE ("57") +57
STRING (+57) "57"
Statistical Example Result
AVERAGE (1,2,3,4) 2.5
MAX (1,2,3,4) 4
MIN (1,2,3,4) 1
SUM (1,2,3,4) 10
Utility Example Result
DATE 6/22/03
TIME 2:55:03
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12. Data Structures and Algorithms
Operators
@ the data connectors within expressions and
equations
@ tell the computer how to process the data
@ tell the computer what type of processing
(mathematical,logical or whatever) needs to be
done
Types of Operator
@ Mathematical - include addition, subtraction,
multiplication, division, integer division, modulo
division, powers, and functions
@ Relational - = , <, >, >=, <=, <>
@ Logical - AND, NOT, and OR
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14. Data Structures and Algorithms
Operators
Logical
A Not A
T F
F T
A B A AND B
T T T
T F F
F T F
F F F
A B A OR B
T T T
T F T
F T T
F F F
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15. Data Structures and Algorithms
Operators
Hierarchy of Operations
( ) Reorders the hierarchy; all operations are
completed within the parentheses using the same
hierarchy.
1. Functions
Mathematical:
2. Power
3. , MOD
4. *, /
5. +, -
Relational:
6. =, <, >, <=, >=, <>
Logical:
7. NOT
8. AND
9. OR
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16. Data Structures and Algorithms
Expressions and
Equations
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 the
variable on the left-hand side of the equal sign is
assigned the value of the expression on the right-
hand side
@ the equal sign does not mean equals; instead it
means replaced by or is assigned the value of
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17. Data Structures and Algorithms
Expressions and
Equations
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