Class Notes: Computer Programming in Pascal

Fall 1997 - Tue 8-9th Period, Thu 9th Period CSE/E221

Instructor: M.S. Schmalz

Project 4 Assignment

• Goal. The purpose of this project is to learn about selection structures, loops, and arrays by getting hands-on experience with Turbo PASCAL.

• Statements. We will be using the following programming statements: Program, Var, Procedure, If-Then-Else, For, WriteLn, ReadLn, and arrays, which we reviewed previously.

• Features. We will be making a procedure that uses arrays and loops and is encapsulated in modular form, as discussed in class.

• Concept. The program Proj4 will compute a price and a cost category given a numerical score between 0 and 100. This will be very much like Project 3, but we will use an array instead of scalar variables for price.

• Algorithm. Program 4 will be structured according to the following pseudocode description, where emboldened text denotes sections of Program 3 that must be revised:

  -------| PROGRAM P-CODE |---------------    -------| IN-LINE COMMENTS |-------
  PROGRAM Proj4:                              ## CGS 3462 - Program 2: Selection
    DECLARE  prave : integer		    ## Main: variable typing
             i,j   : integer
             price : array [1..10] of integer
         cost  : string
    END-DECLARE  
  
    FOR i = 1 TO 3 DO:
      WRITELN('Input Ten Prices [0-100] Separated by Spaces Below:')
  
      FOR j = 1 TO 10 DO:
        READLN(price[j])                            ## Input 10 numbers (keybd.)
      ENDFOR
      Average(price,10, prave)                      ## Take mean of the numbers
  
      Price2Cost(prave,cost)                        ## Convert the mean to cost
  
      FOR j = 1 TO 10 DO:
        WRITELN('price[',j,'] = ', price[j])        ## Display 10 input numbers
      ENDFOR
  
      WRITE " prave= ",prave," cost= ",cost         ## Output results to screen
    ENDFOR
  
  END-PROGRAM
    
  ## CGS 3462 - Cost Category Selection Procedure
  PROCEDURE Price2Cost(price,cost):         ## CGS 3462 - cost Selection Proc.
    DECLARE  price : integer                ## integer "price" - student price
             cost : string                  ## string  "cost" - letter cost
    END-DECLARE  
  
    IF price > 85 THEN                      ## High cost exceeds $85
      cost := 'High'
    ELSEIF price <= 85 AND price > 60 THEN  ## Medium cost is $60 to $85
      cost := 'Medium'
    ELSEIF price <= 60 AND price > 30 THEN  ## Low cost is $30 to $60
      cost := 'Low'
    ELSEIF price <= 30 THEN                 ## Cheap prices are below $30
      cost := 'Cheap'
    END-IF
  END-PROCEDURE
  
  PROCEDURE Average(p,N,d):                 ## CGS3462 - find mean of 3 numbers
    DECLARE  N,d: integer                   ## Inputs and output are integers
             sum: integer
             p  : array [1..10] of integer
    END-DECLARE
  
      sum := 0                              ## Initialize sum
      FOR j = 1 TO N DO:
        sum := sum + p[j]                   ## Accumulate N numbers
      ENDFOR
    d := ROUND(sum/10)                      ## Compute mean using ROUND function
  
  END-PROCEDURE
  
  

• PASCAL Programming Procedure. Enter the preceding p-code in Pascal form using Turbo PASCAL, as we did in class. Here are a few hints that will help you. Follow the directions at the bottom of the page for handing in your project materials:
  Step 1. Declare scope of variables as shown in the p-code.

  Step 2. Use the Price2Cost procedure that you developed for Project #2. This implements the concept of reusable code. The procedure called Average should have the following PASCAL declaration:

   PROCEDURE Average(p : array [1..10] of integer, N: integer; VAR d : integer);
  

  Step 3. Based on your experience with errors in Projects 1-3 and our discussion in class, check to see if there are any errors in the preceding program statements. We will discuss the code in detail in class. However, you still need to check for missing semicolons, or the wrong variables in the IF statement. Now, run the program and see if the output is correct. Play with different values in the array price. If the output is incorrect, why does this occur? Fix any problems that may occur in the preceding code.

  Step 4. Document the program produced in Step 1 by inserting in-line comments using braces ( {} ), and comments in separate lines before the procedure. Examples of in-line comments have been shown in the p-code. You will have to convert the in-line comment for each procedure to a properly structured comment on its own line. Then run the program to produce output. One iteration of the FOR-loop should produce output that looks like this (your input emboldened, DOS prompt not included):

    Input Ten Prices [0-100] Separated by Spaces Below:
    10 20 30 40 50 60 70 80 90 50
    price [1] = 10
    price [2] = 20
    price [3] = 30
    price [4] = 40
    price [5] = 50
    price [6] = 60
    price [7] = 70
    price [8] = 80
    price [9] = 90
    price [10] = 50
    prave= 50 cost= Low
  

• Hardcopy. The completed program (Proj4 together with the output) should be printed on a CIRCA 24-pin printer, or a good-quality printer you may have at home. Laser printer output is acceptable, if you have access to a laser printer. Otherwise, a 24-pin dot matrix printer will do. Staple your two pages (one program, one output page) together and write your NAME, SSN, CGS3462, PROJECT #4, and today's DATE at the TOP RIGHT-HAND CORNER of the paper, in BIG BLOCK LETTERS (so I will not mistake it for someone else's). Be sure to print clearly, so I will know whose program it is.

• Items Due. Give the instructor your completed project hardcopy in class on Thursday 30 October 97. Projects turned in a day late will be penalized -10%; two days late: -20%. Projects turned in after the Friday following the due date will not be accepted unless accompanied by a documented excuse (note from your physician or advisor).