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# 2 beginning problem solving concepts for the computer

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### 2 beginning problem solving concepts for the computer

1. 1. Data Structures and Algorithms Constants and VariablesConstants @ 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 symbolsVariable @ 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 constantBeginning Problem-Solving Concepts for the Computer Page 1 of 17
2. 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.Beginning Problem-Solving Concepts for the Computer Page 2 of 17
3. 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.Beginning Problem-Solving Concepts for the Computer Page 3 of 17
4. 4. Data Structures and Algorithms Data TypesData @ unorganized factsInformation @ 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.Beginning Problem-Solving Concepts for the Computer Page 4 of 17
5. 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 FALSEBeginning Problem-Solving Concepts for the Computer Page 5 of 17
6. 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 StringBeginning Problem-Solving Concepts for the Computer Page 6 of 17
7. 7. Data Structures and Algorithms Data TypesRules 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.Beginning Problem-Solving Concepts for the Computer Page 7 of 17
8. 8. Data Structures and Algorithms Data TypesRules 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.Beginning Problem-Solving Concepts for the Computer Page 8 of 17
9. 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 solutionClasses of Functions: a Mathematical a String a Conversion a Statistical a UtilityBeginning Problem-Solving Concepts for the Computer Page 9 of 17
10. 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" 6Beginning Problem-Solving Concepts for the Computer Page 10 of 17
11. 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 2:55:03Beginning Problem-Solving Concepts for the Computer Page 11 of 17
12. 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 doneTypes of Operator @ Mathematical - include addition, subtraction, multiplication, division, integer division, modulo division, powers, and functions @ Relational - = , <, >, >=, <=, <> @ Logical - AND, NOT, and ORBeginning Problem-Solving Concepts for the Computer Page 12 of 17
13. 13. Data Structures and Algorithms Operators Mathematical Operation Resultant 3.0 + 5.2 8.2 7.5 - 4.0 3.5 8.0 * 5.0 40 9.0/4.0 2 94 2 9 MOD 4 1 3^2 9 Relational Operation Resultant 3=2 FALSE 5>1 TRUE 5=1 FALSE 7 <= 8 TRUE 9>=12 FALSE 10 < 2 TRUE 8<>8 FALSEBeginning Problem-Solving Concepts for the Computer Page 13 of 17
14. 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 FBeginning Problem-Solving Concepts for the Computer Page 14 of 17
15. 15. Data Structures and Algorithms OperatorsHierarchy 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. ORBeginning Problem-Solving Concepts for the Computer Page 15 of 17
16. 16. Data Structures and Algorithms Expressions and EquationsExpression @ processes data, the operands, through the use of operators @ example: LENGTH * WIDTHEquation @ 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 ofBeginning Problem-Solving Concepts for the Computer Page 16 of 17
17. 17. Data Structures and Algorithms Expressions and EquationsBeginning Problem-Solving Concepts for the Computer Page 17 of 17