2 Project 1 n Exercise # 8, page 57 Bohl & Rynn’s textbook n Due date: February 3 rd, 2003
3 Learning Objectives n Understand the relation between Algorithm and Pseudocode or program flowchart n Draw flowcharts n Write pseudocodes
4 Recall form Class 2 & 3 n Use of tools by analyst/programmer in SDLC n Design/Programming tools used for: – Specifying problem-solving logic Pseudocode: English-language statements that describe the processing steps of a program in paragraph form. START READ EMPLOYEE DATA COMPUTE GROSS PAY COMPUTE DEDUCTIONS COMPUTE NET PAY WRITE EMPLOYEE PAYCHECK STOP Example
5 Algorithm ? n Step-by-step procedure to solve a problem n An algorithm can be expressed using: – A System Flowchart – A Program Flowchart – A Pseudocode, etc. n Any algorithm must meet the following requirements: – Use operations from only a given set of basic operations (+,-,/,*, …) – Produce solution in a finite number of such operations
6 Example of algorithm (program flowchart) REGSALES = Regular sales amount SALESALES = Reduced sales amount REGCOM = Regular commission (6%) SALESCOM = Sales commission (3%) PAY = Total pay due Algorithm for determining salespersons’ pay I P O
7 Algorithm vocabulary START STOP SYMBOLS NAME Terminal interrupt symbols USE Terminal point (start, stop, or break) Input/Output symbol Reading data from an input medium or writing data to an output medium Process symbol Processing input data
8 Algorithm vocabulary SYMBOLS NAME Flowline symbol USE Sequence of operations and direction of data flow Decision symbol Decision-making operations Predefined-process symbol Operations specified elsewhere (not in the current algorithm)
9 Algorithm vocabulary SYMBOLS NAME Connector symbol USE Exit to, or entry from, another part of the Flowchart Preparation symbolControl operations: Set limit on loop-control variables, Initialize accumulators, etc.
10 Algorithm vocabulary Variables Data independence Assignment statement Constant Data items whose values may change, or vary during processing Using Variables instead of their specific values gives a program the capacity to perform processing on any set of input data. Statement that assign a value (calculated or not) to a variable A value that doesn’t change REGCOM = REGSALES *.06 READ REGSALES, SALESALES READ $1000, $ ItemMeaningExampleComment 1) Variables names are place- holders for values 2) Variable names are chosen by programmer 3) Names should be descriptive The computer will perform the calculation first, and then, assign the result to REGCOM
11 IFTHENELSE / DECISION SYMBOL Is Condition True ? Processing 1 Processing 2 Processing 3 :::: :::: General form AMOUNT > 200 ? DISCOUNT = AMOUNT *.10 SUBBIL = AMOUNT – DISCOUNT SUBBIL= AMOUNT :::: An Example READ AMOUNT YESNO YESNO Could be many processings,…
12 Exercise 1: Tuition bill Problem Write the program flowchart to prepare a tuition bill. The input will contain the student name, Social Security Number, and total number of credits for which the student has enrolled. The bill will contain the student name, Social Security Number, and computed tuition. Total credits of 10 or more indicate that the student is full-time. Full-time students pay a flat rate of $1000 for tuition. Total credits of less than 10 indicate that the student is part-time. Part-time students pay $100 per credit for tuition. Exercise 11 (Chapter 3)
13 Exercise 1’s solution: ( Part 1: System Flowchart ) (To be done in class)
14 Exercise 1 solution: (Part 2: Program Flowchart ) (To be done in class)
15 Project 1 Write a program flowchart and corresponding pseudocode to solve the following problem: Assume the input for a student is name, student number, and three grades. Output the student name and an S (Success) if the average of the three grades is 65 or more. Otherwise (else), output the student’s name, a U (Unsuccess), and the number of additional points needed for an S.
16 Exercise 2: Billing problem Look at the program flowchart on the next slide, and answer the following questions: (a)For what variables are values read as input ? (b)What variables’ values are output ? (c)What constants are used ? (d)Simulate the execution of this algorithm, assuming the values shown below are read as input for the first four variables named. Exercise 11 (Chapter 2) Blouse Mrs. A. B. Wallace ITEM QTY PRICE AMTOD DISCOUNT NAME SUBBILL TAXES BILL
19 Pseudocode n Other common way to represent algorithms n Similar to programming languages like Visual Basic but – Does not require strict rules as programming languages Start Read NAME, SSN, CREDITS IF CREDITS >= 10 THEN TUITION = 1000 ELSE TUITION = 100 * CREDITS ENDIF Write NAME, SSN, TUITION Stop Pseudocode for Tuition problem (see Slide12) UPPERCASE for variable names UPPERCASE for Reserved words Lowercase for non- reserved words Titlecase
20 Pseudocode Start Read NAME, SSN, CREDITS IF CREDITS >= 10 THEN TUITION = 1000 ELSE TUITION = 100 * CREDITS ENDIF Write NAME, SSN, TUITION Stop Pseudocode for Tuition problem (see Slide12) Use of indentation (i.e. clauses are indented a few positions) for clarity
21 Exercise 3: Weekly Payroll problem Construct a program flowchart and corresponding pseudocode to solve the following problem: ABC company needs a weekly payroll report for its salespeople. Input to the program is a salesperson’s name, number, and weekly sales. Output is the salesperson’s name, number, and pay. Each salesperson receives a base pay of $300 as well as a 10% commission on his or her total sales up to and including $500. Any sales over $500 merit a 15% commission for the employee. (For example, if sales = $600, then pay = $300 + $50 [or.10 * 500] + $15 [.15 * 100] = $350). Use a DOWHILE loop and a counter to compute the weekly payroll for exactly 20 employees. Exercise 19 (Chapter 4)
22 Exercise 3’s solution: ( Part 1: System Flowchart ) NAME, NUM, SALES WEEKLY PAYROLL PROGRAM NAME, NUM, PAY
23 Exercise 3 solution: (Part 2: Program Flowchart ) (To be done in class)
24 Exercise 3 solution: (Part 3: Pseudocode ) (To be done in class)
25 Algorithm Development Process n Design verification, in order to: – Prevent errors from occurring – Detect and correct errors soon n Selection of Review Team members for: – Informal design review or – Structured design review n Structured Design Review: – Selection of representative values of input (data normally expected, extreme values, invalid data) – Following designed algorithms to determine what output are produce.
26 Summary Questions 1. Distinguish between Algorithm on the one hand, and Program flowchart and Pseudocode on the other hand. Discuss the relations between the two. 2. (a) List the main keywords used in Pseudocodes. (b) What control structures they represent. You should know how to design program logic using Program Flowcharts & Pseudocodes (Review Exercises 1,2,3 above & Exercise 15 Ch.4 and answer on page 339)