Solutions to Module 6: Variables and Expressions

Check Your Answers

	Is Your Answer ... ?	If Not, Start With
1.	`VAR_1` `VARIABLE_1`	Lesson 1
2.	`HPPROMPT` or `HPPATH`	Lesson 1
3.	FALSE	Lesson 1
4.	TRUE	Lesson 1
5.	`SHOWVAR VARIABLE1` or `ECHO !VARIABLE1`	Lesson 1
6.	`ECHO HELLO ___ WELCOME TO THE ...` `- OR -` `SETVAR A "HELLO __ WELCOME TO THE ..."` `SHOWVAR A``or` `ECHO !A`	Lesson 2
7.	`INPUT USERNAME;PROMPT="What is your name?"` `ECHO HELLO !USERNAME __ WELCOME TO THE ...`	Lesson 2
8.	You must explicitly dereference the value of `VAR_A` by using the statements in b and c.	Lesson 2
9.	`CFA`: It prints: `* HELLO JULIO FROM SPAIN ` and quits. `CFB`: It prints: ` HELLO JULIO FROM SPAIN ` and reprompts. `CFA`: It prints ` SORRY, NO MESSAGE ` and quits. `CFB`: It prints ` SORRY, NO MESSAGE ` and quits. `CFA`: It prints: ` HELLO GINA FROM ITALY ` and quits. It never gives you a chance to enter the `//`. `CFB`: It prints: `HELLO GINA FROM ITALY **` and quits after you enter `//`.	Lesson 2

Lesson 1 Understanding Variables

Q 6-1

The following are acceptable names for variables:

	Variable Name
b.	`CIERROR`
c.	`FRED_FLINTSTONE`
d.	`HPINPRI`
f.	`_JAMES_BOND`

Q 6-2

According to the values assigned them (by the user or the system), the variables listed below are of the specified type:

	Variable	Type
`HPJOBLIMIT`	(number of jobs allowed to run):	integer
`HPJOBCOUNT`	(number of jobs currently running):	integer
`RESPONSE`	(user response - either Y or N):	string
`FILE NAME`	(user-supplied file name):	string

Q 6-3

Hint: HELP VARIABLESReturn. According to the Help facility, each of the following variables are defined.

Hint: SHOWVAR variablenameReturn

Their current values depend on your system:

Variable	Current Value	Definition
`HPJOBLIMIT`	7	Current job limit.
`HPSESLIMIT`	60	Current session limit.
`HPPROMPT`	:	The initial system prompt.
`HPPATH`	`HPGROUP,PUB`,`PUB.SYS`	Current search path
`HPVERSION`	X.11.50	Current version of operating system.
`HPUSER`	`USER1`	User name.
`HPSESCOUNT`	varies with the system	Current number of sessions.

Q 6-4

To list all the system-defined and user-defined variables, enter this command:

SHOWVAR @

Q 6-5

The system-defined variables in the STATS command file are the following:

   HPJOBLIMIT

   HPJOBCOUNT

Q 6-6

No, neither variable is user-modifiable.

Q 6-7

In the LF command file, the three user-defined variables are:

   RESPONSE

   FILE NAME

   OPTION

Exercise 6-1: Variables

To define a variable called MYPROMPT and assign it the value currently stored in HPPROMPT, enter the following:
SETVAR MYPROMPT HPPROMPT
To display the value of MYPROMPT, enter the following:
SHOWVAR MYPROMPT
To delete MYPROMPT and verify that it is gone, enter the following:
DELETEVAR MYPROMPT SHOWVAR MYPROMPT
MYPROMPT is a user-defined variable.
HPPROMPT is a system-defined variable.
You cannot delete system-defined variables.

********* End of Exercise 6-1 **********

Lesson 2 Using Variables and Expressions

Q 6-8

The method of dereferencing used in the two ECHO statements of the STATS command file is explicit dereferencing (exclamation points are used).

Q 6-9

To give the three user-defined variables, USER, GROUP, and ACCT, the same values as those currently stored in the system-defined variables, HPUSER,HPGROUP, and HPACCT, you would do the following:

   SETVAR USER, HPUSER

   SETVAR GROUP, HPGROUP

   SETVAR ACCT, HPACCT

Q 6-10

According to the IF-THEN statement in the STATS file, the following messages are displayed in each of the following situations:

The current number of jobs is 10 and the job limit is 12.

   ***APPROACHING JOB LIMIT ---

   STREAM JOB LATER

The current number of jobs is 5 and the job limit is 10.

   ***NUMBER OF JOBS IS STILL REASONABLE ---

   STREAM JOB NOW

Exercise 6-2: IF-THEN-ELSE Statement

1.

Your IF-THEN-ELSE statement should look like this:

   IF HPSESCOUNT >= (HPSESLIMIT*3)/4 THEN

      SHOWVAR HPSESCOUNT

      SHOWVAR HPSESLIMIT

      ECHO ***TOO MANY PEOPLE ON SYSTEM --- LOG OFF NOW***

   ELSE

      SHOWVAR HPSESCOUNT

      SHOWVAR HPSESLIMIT

      ECHO *** CURRENT SESSION LIMIT NOT EXCEEDED ***

   ENDIF

****************** End of Exercise 6-2 *************

Q 6-11: As long as you respond with anything other than //, you will be prompted continually for file names.
Q 6-12: To terminate being prompted for any more file names, you must respond with //.

Exercise 6-3: WHILE Loop

Your CF command file should look like this:

   INPUT RESPONSE;PROMPT="Do you want to change the prompt? (Y or N): "

      IF RESPONSE = 'Y' THEN

         SETVAR MYRESP 'N'

         WHILE MYRESP = 'N' DO

             INPUT HPPROMPT;PROMPT="Enter your new prompt (10 char. max): "

             ECHO !HPPROMPT

             INPUT MYRESP;PROMPT="Is this prompt OK? (Y or N): "

         ENDWHILE

      ELSE

         ECHO Current prompt remains in effect !HPPROMPT

   DELETEVAR RESPONSE,MYRESP

When you enter your final prompt, this prompt should be displayed:
USERx:
Use this command to change HPPROMPT to the initial system prompt:
SETVAR HPPROMPT,":"

************ End of Exercise 6-3 ************

Solutions to Module 6: Variables and Expressions

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