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î TURBO-LESSONS - A Pascal Tutorial Version 5.0 Page 72 Copyright 1989 Lyle M. Faurot Lessons 1-16: $10.00 TURBO-LESSON 12. A FUNCTION TO DETECT ERRORS OBJECTIVES - In this lesson, you will learn about: 1. Error detection 2. Using a predefined function 3. Writing your own function 1. Error Detection. In the previous lesson, you found that some input values caused a problem. The function used in PROG11A calculated the cube of a number entered. If the result was outside the range of valid integers the result is wrong but Pascal doesn't alert you to the problem. If you write programs for others to use, you will have to deal with the problem of ERRORS. There are several approaches to error handling: (1) Error detection before it happens - prevent the occurrence of the error. (2) Error detection when it happens - take corrective action. (3) Ignore the error - let the program bomb! The 3rd is not usually acceptable - but may be o.k. in the early stages of program development since you, the programmer, can fix the problem. You may also find alternate ways to program for the same result while avoiding the possibility of the error. The 2nd, error detection when it happens, will be explored later. Input/Output errors are typical examples of this class of errors. In this lesson, you will find ways to detect a problem and prevent its occurrence. ##### DO: In PROG12, examine FUNCTION Cube. The function has been expanded to detect integers which are too small or too large to produce a valid integer cube. If a number is entered which would cause an error, the result is set to 0 instead of the erroneous result. ##### DO: Run PROG12 several times using the following values for input: î TURBO-LESSONS - A Pascal Tutorial Version 5.0 Page 73 Copyright 1989 Lyle M. Faurot Lessons 1-16: $10.00 3, -3, 31, 32, -32, -33, 0 Were all the results as expected? The inputs, 32 and -33, would produce cubes out of the range of valid integers, so these two should have given results of 0. What about 0 as an input? Did you get the correct result? Can you determine whether a result of 0 is valid (0 input) or invalid (input of < -32 or > 31)? Later in this lesson you will write your own function to deal with this problem! 2. Using a Predefined Function. Pascal provides many functions and procedures which are already defined. Some advantages of using predefined subprograms: (1) The subprogram is already debugged. (2) The subprogram doesn't take up room in your program. (3) You can spend your time on more interesting programming, no need to "reinvent the wheel". To use a predefined function, you have to know: (1) The name of the function (2) What goes in (what values do you provide as input?) (3) What comes out (what result is associated with the function name?) The absolute value function, ABS, can be used in PROG12 to illustrate the use of a predefined function. What goes in What comes out 3 --------> [ABS] --------> 3 -5 --------> [ABS] --------> 5 The absolute value function provides a positive number of the same magnitude as the positive or negative number input to the function. ##### DO: î TURBO-LESSONS - A Pascal Tutorial Version 5.0 Page 74 Copyright 1989 Lyle M. Faurot Lessons 1-16: $10.00 Add the following statement after the ReadLn(No) statement in PROG12: WriteLn('Absolute value: ', ABS(No) ); Run the program several times with both positive and negative numbers. NOTE: THERE ARE OFTEN SEVERAL WAYS TO DO THE SAME THING IN PROGRAMMING. YOU SHOULD BE LOOKING FOR WAYS TO DECIDE WHICH OF SEVERAL PROGRAMMING SOLUTIONS IS BETTER IN A GIVEN CASE. The next exercise demonstrates a way to use ABS in the error detection problem. ##### DO: Change the first line of the IF statement in the FUNCTION Cube to: IF ABS(Number) > 31 Test the program with several values. How would you decide whether to use the function, ABS, in the main program or in the function, Cube? Is the action accomplished by ABS of interest to you in getting the cube of a number? If not, it should probably be pushed out of the main program and into the subprogram. 3. Writing Your Own Function. Now, it's your turn. Another approach to the error detection problem uses a second function, which you are about to write! Give the function the name: Has_Valid_Cube The function will have one input: Number of type Integer The type of the function will be: Boolean What the function does: If Number would produce a valid cube, the function, Has_Valid_Cube, will have the value, TRUE. If Number would produce an error, Has_Valid_Cube will have the value, FALSE. ##### DO: Write the function, Has_Valid_Cube. Place it before the main program. It can be either before or after the function, Cube. î TURBO-LESSONS - A Pascal Tutorial Version 5.0 Page 75 Copyright 1989 Lyle M. Faurot Lessons 1-16: $10.00 Look at FUNCTION Cube if you need help with the form of the function declaration or the IF statement needed. ##### DO: In the main program, replace the WriteLn which references Cube with the following: IF Has_Valid_Cube (No) THEN WriteLn('The cube is: ', Cube(No) ) ELSE BEGIN WriteLn('The cube of ',No,' is outside the integer range'); WriteLn('in this version of Pascal.'); END; Test the program with several positive and negative values and values which would cause erroneous cubes. (If you have trouble writing the function, PROG12A is available as a sample. Don't check PROG12A until you have given it a try on your own!) Are there any other improvements you want to make to PROG12? FUNCTION Cube still checks for invalid inputs. Is this still necessary? ##### DO: Change FUNCTION Cube so that it does no error checking, just calculates the cube of the number input. Test the program with several values including 0. Note that there is no longer any ambiguity when the result is a cube of 0. î TURBO-LESSONS - A Pascal Tutorial Version 5.0 Page 76 Copyright 1989 Lyle M. Faurot Lessons 1-16: $10.00 TURBO-LESSON 13. STRINGS OBJECTIVES - In this lesson, you will learn about: 1. Strings 2. String replacement statement 3. Predefined string function, LENGTH 1. Strings. You have already seen some Pascal strings in the WriteLn statements of earlier lessons. WriteLn('This is a string.'); It is often convenient to store strings as variables or constants. A string constant may be defined in the CONST section: CONST String_1 = 'TURBO-LESSONS'; String variables must be declared in the VAR section. The form of the declaration is: VAR First_Name : String[12]; This sets up storage for a variable named First_Name which can store a string up to 12 characters long. 2. String Replacement Statement. The replacement statement for strings is: String_Name := (string expression); ##### DO: Examine PROG13. Notice the following: A string constant, S_Test is given the value 'Test String' in the CONST declaration section. Several string variables are defined in the VAR section. ##### DO: Run the program. î TURBO-LESSONS - A Pascal Tutorial Version 5.0 Page 77 Copyright 1989 Lyle M. Faurot Lessons 1-16: $10.00 What happens when an attempt is made to store too long a string in a string variable? ##### DO: Add the following to the program: S5 := S_Test; WriteLn(S5); Run the program. How many characters of S5 are printed? ##### DO: Modify WriteLn(S5) to: WriteLn('[', S5, ']'); Run the program. How many characters of S5 are printed? DEBUGGING NOTE: When working with strings, you may find it helpful to print some kind of marker before and after a string to help "see" the occurrences of the character, blank. You have seen what happens when storing 'Test String' in too short a variable: S3 holds 'Tes', S8 holds 'Test Str'. What happens when a string is stored in a variable that is larger than needed? Are blanks added? ##### DO: Modify the WriteLn(S14) to bracket S14 (like you did above with S5) and run the program. How many characters of S14 were printed? Were extra blanks added? (More on this later.) ##### DO: Look at PROG13A. (Don't forget you can Zoom to full screen with F5 to get a better look at the program in the Edit window.) WriteLn(S8[I]); Notice the use of the square brackets in the statement above. This is a way to refer to a specific character in a string. S8[2] means the 2nd character in the string, S8. NOTE: SQUARE BRACKETS ARE USED IN TWO DIFFERENT WAYS WITH STRINGS. WHEN DECLARING VARIABLES, THE BRACKETS ENCLOSE THE MAXIMUM LENGTH î TURBO-LESSONS - A Pascal Tutorial Version 5.0 Page 78 Copyright 1989 Lyle M. Faurot Lessons 1-16: $10.00 OF THE STRING. IN PROCESSING STATEMENTS, THE NUMBER IN THE BRACKETS DESIGNATE A PARTICULAR CHARACTER IN A STRING. ##### DO: Run the program, using 2 as position number. Try 5 as an input. What character was stored as the 5th character of S8? The string stored in S8, 'TURBO', is 5 characters long but S8 is 8 characters long. What characters, if any, are stored in S8[6], S8[7], and S8[8]? ##### DO: Run the program with input values of 6, 7, and 8. What characters were printed? ##### DO: Terminate the program by entering -1 as position number. ##### DO: Change the first statement as the first statement in the BEGIN END block from S8:= S_Test; to S8 := '12345678'; Run the program again, using 6, 7, and 8 as input. What do you conclude about "unused" positions in a string? Before you are prompted to enter the "position number", S8 is printed. Do positions 6, 7, 8 of the string print? Why? 3. Predefined String Function, LENGTH. Because the length of a string is often needed in processing, the function, LENGTH, has been provided for that purpose. ##### DO: Add the following statement after the UNTIL statement: WriteLn('Length of string: ', LENGTH(S8) ); Run the program. ##### DO: î TURBO-LESSONS - A Pascal Tutorial Version 5.0 Page 79 Copyright 1989 Lyle M. Faurot Lessons 1-16: $10.00 Just before the END, insert: FOR I := 1 to LENGTH(S8) DO WriteLn('Position ', I:2, ': ',S8[I]); Run the program. ##### DO: Change the statement S8 := '12345678' to: S8 := 'OK'; Run the program. Also try 'Wake Up' as a value for S8. î TURBO-LESSONS - A Pascal Tutorial Version 5.0 Page 80 Copyright 1989 Lyle M. Faurot Lessons 1-16: $10.00 TURBO-LESSON 14. INTRODUCTION TO PROCEDURES OBJECTIVES - In this lesson, you will learn about: 1. PROCEDURE declaration 2. Using a Procedure 3. Using Parameters 4. A counter with error checking 1. PROCEDURE Declaration. The PROCEDURE subprogram is similar to the FUNCTION subprogram introduced in an earlier lesson. The form of the declaration is: PROCEDURE Add(No_1, No_2 : Integer; VAR Sum : Integer); BEGIN Sum := No_1 + No_2; END; Add is the name of the Procedure. No_1, No_2, and Sum are integer variables called "parameters". VAR in front of Sum indicates that this parameter is a "two-way street". It can receive data from the calling program, and return data to the calling program. No_1 and No_2 can only receive data from the calling program. The BEGIN END block defines the processing performed by the procedure: Add the value in the memory location, No_1, to the value in memory location, No_2, and place the result in the memory location, Sum. 2. Using a Procedure. A reference to this procedure in the main program (or another procedure or function) would have the following form: Add(2, Count, Adjusted_Count); The procedure is "called" or utilized by simply using its name as a statement. (When you define a Procedure or Function, you are adding additional "statements" to your programming language.) Notice that there are three "parameters" here, and three in the Procedure declaration. The three here are associated with the ones in the declaration by position. î TURBO-LESSONS - A Pascal Tutorial Version 5.0 Page 81 Copyright 1989 Lyle M. Faurot Lessons 1-16: $10.00 The first parameter here, the integer, 2, provides input to the first parameter of the procedure, No_1. The second, the variable, Count, provides input to the second parameter of the procedure, No_2. The third, Adjusted_Count, provides input to the third parameter of the procedure, Sum. Since Sum is declared VAR, variable, it also provides output back to Adjusted_Count after the procedure does its calculation. In the Main Program In Procedure Add 2 ----------> No_1 { When Procedure } Count ----------> No_2 { is called } Adjusted_Count ----------> Sum { } -------------------------------------------------------------- Adjusted_Count <---------- Sum { When Procedure ends } ##### DO: Inspect PROG14. ##### DO: Add the following to the watch window: Adjusted_Count, Count, Sum, No_1, No_2. ##### DO: Press F7 to begin tracing. Notice the Procedure variables, No_1, No_2, and Sum are "Unknown identifiers" at this point. Count and Adjusted_Count have "leftover" values--whatever happens to be in the memory assigned to these 2 variables. ##### DO: Trace the Write and ReadLn statements. Enter 4. Stop when the ADD statement is highlighted. Watch carefully what happens in the next step, when you trace the ADD statement. No_1, the first "parameter" in the Procedure ADD should receive the value 2, which is the first value listed in the ADD statement in the main program. No_2 should receive 4, the value of Count. Sum should receive the value of Adjusted_Count. ##### DO: Press F7 once to trace the ADD statement. ##### DO: î TURBO-LESSONS - A Pascal Tutorial Version 5.0 Page 82 Copyright 1989 Lyle M. Faurot Lessons 1-16: $10.00 Trace the Sum:=No_1 + No_2 statement. Which variables changed? ##### DO: Trace the rest of the program. Watch the values of No_1, N0_2, and Sum when the program goes from the procedure ADD back to the main program. ##### DO: Add the following statement as the first statement in the main program: Adjusted_Count := 10; Run the program. Does it make any difference what value is stored in Adjusted_Count before Procedure Add is referenced? Look at the procedure - is Adjusted_Count used as an input for the calculation, or only as a result? 3. Using Parameters. You have already been using parameters, but in this section, you will see a little more of the power and flexibility of parameters. ##### DO: Change the Add statement in the main program to: Add(2, 2, Adjusted_Count); Run the program. Is the result as expected? ##### DO: Change the Add to: Add(Count, Count, Adjusted_Count); Run the program. Any surprizes? ##### DO: Change the Add to: Add(2, 3, 4); Run the program. What happened? The compiler refused to accept 4 as a variable identifier. î TURBO-LESSONS - A Pascal Tutorial Version 5.0 Page 83 Copyright 1989 Lyle M. Faurot Lessons 1-16: $10.00 The VAR preceding Sum in the procedure declaration puts a limit on the corresponding parameter in the calling program: it has to be a variable location to receive the value of Sum when the procedure finishes its calculation. The first two parameters in the procedure, No_1 and No_2, are used only for input to the procedure - they do not provide any output back to the corresponding parameters in the calling program. For this reason, the first two parameters in the calling program are less restricted. They can be constants, variables, or expressions, as long as they are of the same type, integer, as the corresponding parameters in the procedure. ##### DO: Change the Add statement: Add(4, 2 * Count + 5, Adjusted_Count); Run the program. Does the expression work o.k. as a parameter? ##### DO: Change the Add to: Add(Count, Count, Count); Also change the WriteLn to print the value of Count instead of Adjusted_Count. Run the program. Any problems? 4. A Counter with Error Checking. You could use the Procedure Add as a counter by using the following call: Add(Count, 1, Count); The procedure would add 1 to Count and put the result in Count. You could accomplish the same thing with the statement: Count := Count + 1; So why bother to use the procedure? What if Count reaches the upper limit of the integer range, 32767? In the main program you could expand the counting statement to: IF Count < 32767 THEN î TURBO-LESSONS - A Pascal Tutorial Version 5.0 Page 84 Copyright 1989 Lyle M. Faurot Lessons 1-16: $10.00 Count := Count + 1 ELSE WriteLn('Counter reached upper limit'); PROGRAMMING NOTE: HOW DO YOU DECIDE WHAT GOES INTO THE MAIN PROGRAM AND WHAT TO PUT IN SUBPROGRAMS? FROM THE FOLLOWING DISCUSSION, TRY TO FORMULATE AT LEAST ONE RULE FOR MAKING THIS DECISION. This looks a little messy, maybe you should use a procedure to get this out of the main program. Not a bad reason, but there's a more important reason: Ask yourself, "How much of the processing in the IF statement above is of interest in the main program?" Probably only the fact that a count is being incremented. The error checking and how it is done is probably of little interest and just clutters up the main program. ##### DO: Write your own procedure to increment the counter, Count. Call the procedure, Increment. Check for the upper limit of the integer range. (The IF statement above would be one way.) Note that only one parameter is needed, preceded by VAR. ##### DO: In the main program, add the following to check out your procedure: FOR I := 1 to 10 DO BEGIN Increment(Count); WriteLn('Count = ', Count); END; Run the program using the following values as input for count: 0, 3, -34, 32760 (PROG14A is provided in case you need help.) You could also write a procedure, Decrement, to decrease a counter. Note that the error checking would be checking the lower limit, - 32768, or perhaps 0 depending on how you intended to use the counter. î TURBO-LESSONS - A Pascal Tutorial Version 5.0 Page 85 Copyright 1989 Lyle M. Faurot Lessons 1-16: $10.00 TURBO-LESSON 15. INTERACTIVE SCREEN HANDLING OBJECTIVES - In this lesson, you will learn about: 1. Setting up a Data Entry Screen 2. Being nice to users - ClrScr 3. Getting around the screen - GotoXY 4. Screen messages and accepting user input 1. Setting up a Data Entry Screen. For most computer processing applications you will need to provide for entry of data. This is one of the points where your programs interact with the person using the program. How your programs are viewed by those using them will depend on how well you manage the user-computer interaction on the screen. In this lesson you will try some of the basic techniques of screen handling for data entry. NOTE: Some of the programs have the statement Repeat Until KeyPressed; as the last statement. This statement serves to keep the program from ending until you press a key to end the program. Anytime you see this statement at the end of a program, remember that you must press a key to end the program. The reason for adding this statement is to allow you to view the output screen after the program runs. Without it, the Edit screen covers up most of the output screen as soon as the program is done. In this lesson you need to see the whole output screen. ##### DO: Run PROG15. Take a look at the program to see how this screen was produced. ##### DO: Experiment with PROG15. Run the program after each of the following: (1) Add or delete spaces in the WriteLn statements to move the various items. î TURBO-LESSONS - A Pascal Tutorial Version 5.0 Page 86 Copyright 1989 Lyle M. Faurot Lessons 1-16: $10.00 (2) Line the prompts up on the left. You may want to keep the colons in a vertical column after you move the prompts. 2. Being Nice to Users - ClrScr. Pascal provides a predefined procedure to clear the screen. Screen interaction will go smoother if unnecessary items are removed when no longer needed. ##### DO: Add the following statement as the first statement in the main program: WriteLn('This is something leftover from previous processing'); ##### DO: Run the program. How does the data entry screen look now? There are often things left on the screen that need to be cleared away for a better screen presentation. The procedure, ClrScr, will clear the screen. Where should you put ClrScr, in the main program, or in the procedure? Right! In the procedure, because clearing the screen is really just a part of printing the entry screen. ##### DO: At the beginning of the Procedure, Print_Entry_Screen, add: ClrScr; Run the program. Is the "leftover" message gone? NOTE: YOU SHOULD ALWAYS CLEAR THE SCREEN AS NEEDED. EARLIER VERSIONS OF TURBO CLEARED THE SCREEN AT THE BEGINNING OF THE PROGRAM, BUT THAT IS THE TYPE OF THING YOU SHOULD NOT DEPEND ON. WHAT IF THE NEXT VERSION CHANGES? 3. Getting Around the Screen - GotoXY. Cursor positioning is done with the predefined procedure, GotoXY. To find out how it works, try PROG15A. î TURBO-LESSONS - A Pascal Tutorial Version 5.0 Page 87 Copyright 1989 Lyle M. Faurot Lessons 1-16: $10.00 ##### DO: Examine PROG15A, then run it a few times using the following values for X and Y: X Y 1 20 40 1 70 23 Does GotoXY work the way you expected? If that is the way you expected it to work, no problem. If you, like me, find that X and Y seem to be reversed, you can either learn to use GotoXY as is, or write a procedure to make it work the way you want it to! ##### DO: Load PROG15B. The following procedure has been added before the main BEGIN END block: PROCEDURE Locate(X, Y : Integer); BEGIN GotoXY(Y, X); { Note the reversed Y, X here } END; Also notice that the GotoXY(X, Y) statement in the main program has been changed to: Locate(X, Y); Run the program several times using the values: X Y 1 50 10 1 23 70 My own choice is to use GotoXY as is, but if you work in both Pascal and Basic at the same time, you might want some procedure like Locate, to make the cursor positioning work the same in both. Now you know how to get around the screen. You're on your way toward friendly input screens! î TURBO-LESSONS - A Pascal Tutorial Version 5.0 Page 88 Copyright 1989 Lyle M. Faurot Lessons 1-16: $10.00 TURBO-LESSON 16. REAL NUMBERS OBJECTIVES - In this lesson, you will learn about: 1. Range of Real Numbers 2. Input/Output of Real Numbers 3. Calculations with Real Numbers 4. Calculations with Integers and Real Numbers 1. Range of Real Numbers For business processing (dollar amounts), and scientific processing, integers alone are not adequate. Decimal numbers and sometimes numbers in scientific notation are needed. TURBO provides Real Numbers with 11 significant digits of precision in the range: 1E-38 to 1E+38. TURBO also has several other types of Real numbers with other ranges and precision. ##### DO: Set the lower window to Output and run PROG16. Enter 444.333222111 and examine the result presented in scientific notation. How many digits are retained before the E? (I counted 11, including digits on both sides of the decimal point.) This is the 11 significant digits of precision. Note that the last 1 you entered was dropped. 2. Input/Output of Real Numbers. You will need to know what to expect with various combinations of input and output of real numbers. ##### DO: Run PROG16. Enter 444.333222111 and study the various outputs. When the real number, A, is output without any formatting, scientific notation is used: 4.4433322211 are the significant digits. E+02 means multiply by 10 to the 2nd power to get the number. î TURBO-LESSONS - A Pascal Tutorial Version 5.0 Page 89 Copyright 1989 Lyle M. Faurot Lessons 1-16: $10.00 If you want the number presented in some other form, you can add the :w:d formatting to the name of the variable to print. :w Width of the print field :d Decimal positions to print WriteLn(A:10:2); This statement would print the number, A, in a print field 10 characters wide, with 2 decimal positions. Look at the outputs on the screen again. The formats used are printed at the left. Square brackets are printed to show the width of the field and where the number is printed (left or right- justified). :-w Width of print field, left-justify the number. Notice the use of the minus sign to force printing of the number at the left of the field. ##### DO: Trace the program. What happens to the total width of the print field when numbers are printed left-justified? ##### DO: Run PROG16 with 3.4567 as input. What happens when a print format is specified which will not hold all of the significant digits? Is the number rounded? 3. Calculations with Real Numbers. ##### DO: In PROG16 change the ReadLn(A) to ReadLn(B). Add after ReadLn(B): A := B + C; The result printed will be the sum of B, which you enter, and C which is a constant, -2.0. Run the program with 2.34 as input. Are the results as expected? In scientific calculations, very large, and very small numbers are sometimes needed. Can you enter these in a convenient form without a long string of zeros? î TURBO-LESSONS - A Pascal Tutorial Version 5.0 Page 90 Copyright 1989 Lyle M. Faurot Lessons 1-16: $10.00 The radius of the earth is 6370000 meters. This is the same as 6.37 times 100000 Which is the same as 6.37 times 10 to the 6th power Which may be entered as 6.37E6 or 6.37E06 or 6.37E+6 or 6.37E+06. ##### DO: Change ReadLn(B) back to ReadLn(A) and remove the next statement, A:=B+C; ##### DO: Run the program with 6.37E6 as input. Try the other 3 forms listed above. Are the results the same in all cases? ##### DO: Run the program with 6370000 as input. Does it make any difference whether the number is input in scientific notation or in the usual form? ##### DO: Run the program with 6.37E7 as input. What happens when the result is too large for the format? (Count the character positions used to print A:10:2. Include the decimal point as one position). ##### DO: Try 6.37E18 as input. For future reference, remember this possibility where the number is too large. Several numbers printed on the same line may not be in the right place if one number is too large and "pushes" the others farther right on the print line. ##### DO: Run the program with 6.37E-6 as input. Notice the unformatted output is correct, but the formatted output shows nothing but zeros. The result, A, is 0.00000637, with significant digits too far to the right to show up in the formatted output. ##### DO: î TURBO-LESSONS - A Pascal Tutorial Version 5.0 Page 91 Copyright 1989 Lyle M. Faurot Lessons 1-16: $10.00 Change the WriteLn format, A:10:2 to A:10:6. (Notice there are two A:10:2's in the statement, the first is a screen message, the second is the actual format.) Run the program with the following values: 6.37E6, 6.37E-6, 6.37E-4 4. Calculations with Integers and Real Numbers. What happens when you mix Integers and Real numbers in calculations? ##### DO: Get a copy of the original PROG16 and make the following changes: Change ReadLn(A); to ReadLn(I); Change the prompt to Write('Enter an Integer: '); Add after the ReadLn statement: J := I + C; Run the program. What results did you get? The "Type mismatch" refers to J. Since the calculation involves both an integer, I, and a real number, C, the result cannot be stored in an integer variable. If the result had significant digits after the decimal, they would be lost when stored as an integer. ##### DO: Change the calculation to: A := I + C; Run the program. NOTE: ON YOUR OWN, YOU MAY WANT TO EXPERIMENT WITH THE WRITELN FORMATS. CHANGE THE FORMATS TO VARIOUS VALUES AND TRY THEM WITH A VARIETY OF INPUTS. î TURBO-LESSONS - A Pascal Tutorial Version 5.0 Page 92 Copyright 1989 Lyle M. Faurot Lessons 1-16: $10.00 A CHALLENGE One of the objectives stated at the beginning of these lessons was to "provide the basics you need to get started with Pascal and build your confidence and enthusiasm to continue learning on your own". I want to challenge you now to write some programs of your own. Right away! Don't wait--get started. If you make mistakes, Turbo Pascal has some great tools to help you correct them. You may be surprized how soon you will be writing very useful programs. Watch for the next TURBO-LESSONS. Be sure to let me know what lessons you would like: More Turbo Pascal, QuickBasic, C, word processors, spreadsheets, something else? Thanks for your support of TURBO-LESSONS and Shareware.