Chapter 3 - Revision history

Mikhail.zheleznov: formatting

2019-03-14T21:17:11Z

formatting

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	If you now do a LIST of your program, it should look like this:		If you now do a LIST of your program, it should look like this:


	[[image:3.1.png]]		[[image:3.1.png]]

Mikhail.zheleznov: formatting

2019-03-14T21:11:42Z

formatting

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	===GO===		===GO===
	As soon as you have entered the GO command and pressed ENTER, you can go through the steps illustrated in the following frame. The INPUT prompt in the left corner of the status line reminds you that you must enter information before the program can continue:		As soon as you have entered the GO command and pressed ENTER, you can go through the steps illustrated in the following frame.

			The INPUT prompt in the left corner of the status line reminds you that you must enter information before the program can continue:


	[[image:3.3.png]]		[[image:3.3.png]]

Mikhail.zheleznov: clarification

2019-03-06T12:18:41Z

clarification

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	c) Every line label must begin with a letter.		c) Every line label must begin with a letter.

	2) ~~Identify~~ the ~~possible~~ line labels ~~in the following list~~:		2) Which of the following can be used as line labels:

	a) PRINT <br>		a) PRINT <br>

Mikhail.zheleznov: clarification

2019-03-06T12:17:08Z

clarification

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	====Quick Quiz 3.4 ====		====Quick Quiz 3.4 ====
	1) ~~Identify~~ the true ~~statement~~:		1) Which of the following statements is true:

	a) Line labels can be up to 30 letters, numbers and underscores long. <br>		a) Line labels can be up to 30 letters, numbers and underscores long. <br>

Mikhail.zheleznov: Took out Meyerbottom, but left Zippy in. Let's just compromise here. I personally enjoy the theatrics, but they are confusing beginner users who may be struggling with English as a second language. All the slang in the documentation knocks them off track.

2019-03-06T12:14:59Z

Took out Meyerbottom, but left Zippy in. Let's just compromise here. I personally enjoy the theatrics, but they are confusing beginner users who may be struggling with English as a second language. All the slang in the documentation knocks them off track.

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	To see how well this error condition works, RUN your program. When the "Total number of miles?" question comes up, enter letters instead of numbers again. Try to imagine the execution order of your program as it is running. It might help to envision Zippy the Cursor dashing along from one statement to the next, executing each one. When Zippy reaches the INPUT statement in line 20 or 40, he patiently stands by (right next to the MI manila folder) and waits for you to enter a number that he can assign to MI. But when you enter letters instead, he double-checks line 20 or 40 to see if you told him what to do for such an error. Why yes! The CONV 80 portion of the line is practically screeching at him to go to line 80. So he takes a flying leap to line 80 (he even flew past the STOP statement in line 70), where he discovers that you want him to retry the error-causing statement. Back he goes to line 20 or 40, wherever the error had occurred, where he again patiently waits for you to enter a number.		To see how well this error condition works, RUN your program. When the "Total number of miles?" question comes up, enter letters instead of numbers again. Try to imagine the execution order of your program as it is running. It might help to envision Zippy the Cursor dashing along from one statement to the next, executing each one. When Zippy reaches the INPUT statement in line 20 or 40, he patiently stands by (right next to the MI manila folder) and waits for you to enter a number that he can assign to MI. But when you enter letters instead, he double-checks line 20 or 40 to see if you told him what to do for such an error. Why yes! The CONV 80 portion of the line is practically screeching at him to go to line 80. So he takes a flying leap to line 80 (he even flew past the STOP statement in line 70), where he discovers that you want him to retry the error-causing statement. Back he goes to line 20 or 40, wherever the error had occurred, where he again patiently waits for you to enter a number.

	But wait a second. Pretend that you are ~~Winston M. Meyerbottom~~ now. You entered "three hundred" for the number of miles and Zippy did all that work just so you wouldn't have to deal with an error mode, but now nothing is happening on the screen. The only clue as to what should be done is the INPUT prompt in the status line, and who knows what that means (besides you, the computer programmer)?		But wait a second. Pretend that you are the user now. You entered "three hundred" for the number of miles and Zippy did all that work just so you wouldn't have to deal with an error mode, but now nothing is happening on the screen. The only clue as to what should be done is the INPUT prompt in the status line, and who knows what that means (besides you, the computer programmer)?

	You know that Zippy is eagerly waiting, with MI manila folder open, for that number so go ahead and enter it, then let Zippy finish the program with no more mishaps.		You know that Zippy is eagerly waiting, with MI manila folder open, for that number so go ahead and enter it, then let Zippy finish the program with no more mishaps.

Mikhail.zheleznov: clarification

2019-03-06T12:11:10Z

clarification

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	===3.3 Program Operation===		===3.3 Program Operation===
	In the last section, you learned what to do when a run-time error occurs. But what happens when you give your MILEAGE program to somebody ~~like Winston M. Meyerbottom (~~who knows nothing about programming~~) and he causes~~ an error ~~to occur~~? How will he know what went wrong, and how will he know how to get out of error mode?		In the last section, you learned what to do when a run-time error occurs. But what happens when you give your MILEAGE program to somebody who knows nothing about programming encounters an error? How will the user know what went wrong, and how will he/she know how to get out of error mode?

	A partial answer to this problem is that you can code error conditions into your programs that catch (or trap) specific kinds of errors. For instance, the kind of error that you caused by entering letters instead of number was called a conversion (CONV) error.		A partial answer to this problem is that you can code error conditions into your programs that catch (or trap) specific kinds of errors. For instance, the kind of error that you caused by entering letters instead of number was called a conversion (CONV) error.

Mikhail.zheleznov: slight correction and formatting

2019-03-06T12:08:46Z

slight correction and formatting

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	Now press ENTER. The following things should happen: one, the computer should beep; two, error code [[0726]] should appear in the center of the status line; and three, the word ERROR should appear in the left corner of the status line. This is called an "user error or run-time error because the error occurred when the user was running the program.		Now press ENTER. The following things should happen: one, the computer should beep; two, error code [[0726]] should appear in the center of the status line; and three, the word ERROR should appear in the left corner of the status line. This is called an "user error or run-time error because the error occurred when the user was running the program.

	A '''run-time error''' is an error detected ~~after or~~ during the execution a program		A '''run-time error''' is an error detected during the execution a program.

	As signified by the word ERROR in the status line, your program is now in error mode. When a program enters this mode, it stops executing and waits for instructions in the form of commands from the user. This leaves plenty of time for you to look up the error code in the Wiki.		As signified by the word ERROR in the status line, your program is now in error mode. When a program enters this mode, it stops executing and waits for instructions in the form of commands from the user. This leaves plenty of time for you to look up the error code in the Wiki.

Mikhail.zheleznov: clarification

2019-03-06T12:05:18Z

clarification

← Older revision		Revision as of 12:05, 6 March 2019
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	====Extra Practice: ====		====Extra Practice: ====
	Write a program which calculates the area of a circle. Use the INPUT and LET statements and ~~save~~ it ~~under the name~~ Area.		Write a program which calculates the area of a circle. Use the INPUT and LET statements, calculate the area and assign it to a variable named Area.

	As you progress through the next few chapters, we’ll continue to build on and modify this program as you learn different statements and commands.		As you progress through the next few chapters, we’ll continue to build on and modify this program as you learn different statements and commands.

Mikhail.zheleznov: This was reported by a beginner BR student to be confusing, so I took out some of the dramatics

2019-03-06T11:54:48Z

This was reported by a beginner BR student to be confusing, so I took out some of the dramatics

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	00010 PRINT "Total number of miles?"		00010 PRINT "Total number of miles?"

	This statement asks a question that the user must answer~~. We know this, you know this, and the user will know this as soon as they see the question, but Business Rules! doesn't know this yet~~.		This statement asks a question that the user must answer.

	~~You~~ must use the INPUT statement to ~~specifically~~ tell ~~Business Rules! that its next step is~~ to wait for and accept information from the user:		Next, you must use the INPUT statement to tell BR to wait for and accept information from the user:

	00020 INPUT MI		00020 INPUT MI

Laura: /* Chapter Exercise */

2013-08-16T17:09:35Z

Chapter Exercise

← Older revision		Revision as of 17:09, 16 August 2013
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	[[Solutions#CHAPTER 3\|Solution]]		[[Solutions#CHAPTER 3\|Solution]]

	NEXT:[[Chapter 4]]		NEXT:[[Chapter 4\|Constants and Variables]]

	[[BR Tutorial\|Back to Index]]		[[BR Tutorial\|Back to Index]]