TweetFollow Us on Twitter

Subprograms
Volume Number:2
Issue Number:2
Column Tag:Special Projects

Subprograms in Basic Explained

By Mike Steiner, Sierra Vista, AZ, MacTutor Contributing Editor

Versatile Input Routine

So, you are writing a program in Microsoft BASIC and the user of the program has to supply information for the program to process. The tradtional, and - before Microsoft BASIC for the Macintosh - sometimes the only available, way for a BASIC program to obtain data from the keyboard is via the INPUT statement. This yeoman method has worked for many years and has proven its worth. It also has shown all its faults. In some varieties of BASIC, certain characters (notably the comma and colon) cannot be read by INPUT. Unless you incorporate error checking routines (which can require extensive programming), the only way the user can correct errors is for him to notice the error before he presses Return so that he can backspace and retype his data. Error checking routines range from a simple

INPUT "Do you want to make any changes? (Y/N) "; YN$

followed by more questions and INPUT statements, to complex screen structures with vertical and horizontal tabbing combined with the INPUT statement.

If the program uses formatted displays, then more programming effort may be required to reformat the screen for the display after each INPUT sequence.

Microsoft BASIC for the Macintosh (Version 2.0 or later) has some built-in features that can help you alleviate some, if not all, of these problems. Formatted screen displays can be kept intact by overlaying windows for the input routines. INPUT can be replaced by EDIT FIELD and EDIT$ to provide a powerful error-checking routine that allows the operator to check all of his data before signifying that everything is correct and proceeding to the next task.

Listing 1 contains a routine just for this purpose. The routine is in the form of a subprogram so that it can be inserted anywhere in your program. Sub- programs are, to my knowledge, unique to the Macintosh version of BASIC. They are independent modules that can be anywhere within a program listing and are completely ignored by BASIC unless they are CALLed by the program. All variables used by a subprogram remain with the subprogram and do not affect the variables in the main program unless explicitly allowed to do so by the program. If A = 10 in the main program and a subprogam sets A equal to 136.43, when the subprogram exited, A would still equal 10 in the main program. Pascal programmers will recognize subprograms as being very similar to Pascal's procedures.

The listing has two parts. The first is an example of a main program for the subprogram to work within. The second is the the subprogram itself.

The main program starts by setting all variables as integers. It then DIMensions the arrays label$, info$, and corner. Label$ contains the names of the edit fields; info$ holds the actual information inputted, and corner defines the four corners of the main window. Next, the label$ and corner data are read into their respective arrays and some sample text is printed in the window. The program then CALLs the subprogram, which is named inputroutine. (Note that the keyword “CALL” is optional.) After the subprogram is exited, the main program transfers the data from the general array to individually named variables. It then formats and prints the data and asks whether the user wants to redo the operation and then waits for a key press to end or redo the program.

Fig. 1 Program Output

Look at the line “doitagain” in the main program. This line calls the subroutine. The list following the subprogram's name contains those variables that are passed to the subprogram. If a variable is not in this list, it is not passed to the subprogram. Corner, info$ and label$ each has a pair of parentheses after it. This is to tell BASIC that these elements are array variables.

In addition to passing variables, you can also pass expressions. As an example, if you need to pass the area of a circle to a subprogram called computeit, but computit does not need to know the radius, you can pass the area like this:

CALL computit (3.14159 * radius ^ 2)

Subprograms cannot change the values of expressions passed to it; they can change only the values of variables. If you need to pass a variable and want to make sure that the subprogram will not change its value, place parentheses around the variable and it will be passed as a value by expression.

Now let's look at the subprogram itself. The first line starts with SUB to indicate that it is a subprogram. The next part of the line is the subprogram's name, followed by a variable list in parentheses. The line concludes with the keyword STATIC.

The subprogram next defines the sizes of window 2 and the portion of window 1 that will be hidden by window 2. It continues by dimensioning the rectangle array that will hold the screen behind window 2; then it defines the shape of the text cursor. The next line, which starts with the ketyword GET, stores the about to be covered portion of window 1 in the previously dimensioned rectangle array. Window 2 is then opened, covering a portion of window 1.

Then the subprogram goes to the subroutine “refresh.” This routine clears the window, sets the font to 0 (Chicago), and prints the labels for the edit fields. It then returns to the main part of the sub program. This subroutine is accessed whenever a portion of the window is covered by another window such as the command or a list window.

The subprogram then resets the font to the default font (Geneva) and draws the edit fields and an OK button. When the edit fields are drawn, the latest information generated in those fields are placed into them for editing. This helps when a field remains the same from one record to another. Because the text in each field is selected when the field is first chosen by tabbing to it, putting in new data is not any more difficult than if the field were left blank..

The next line flushes any dialog actions from memory and then allows the program to continue by initializing and entering a WHILE loop. The first block of programming within the loop monitors the cursor position on the screen and whenever the cursor moves into an edit field, changes it to an I-beam to show text insertion. When the cursor moves outside of the edit field, it reverts to the default arrow. If you have fewer than 10 edit fields, you will need to make minor modifications to this portion of the program.

The next block looks for dialog actions. The only dialog events it recognizes are clicking in the OK box or in an edit field, pressing the Return or Tab key, or obscuring the window with another window.

If the window is obscured, the program goes to the refresh subroutine which clears the window and reprints the field labels. Neither the CLS statement nor covering the window affect buttons or edit fields (including their contents), so they do not need to be refreshed.

If the dialgog event shows that the Tab key had been pressed or that the mouse was clicked in an edit field, the program goes to the tabfield subroutine. If the Tab key had been pressed, the routine increments or decrements the current edit field by 1. Note the line “shiftkey = (PEEK (379) and &H1) * 2.” Peeking memory location 379 monitors various keys on the keyboard. If bit 0 is set, that means that the shift key has been pressed. By ANDing location 379 with the value 1, the result is 1 if the shift key has been pressed and is 0 if it has not been pressed. If the TAB key has been pressed, rather than the mouse clicked in the and edit field, the next line subtracts the value shiftkey (which is either 2 or 0) from the value of currentfield + 1. Therefore the value of currentfield is increased by 1 if the TAB key has been pressed and the shift key has not been pressed. But, if both the shift and TAB keys have been pressed, then currentfield is decreased by 1. This allows for reverse tabbing. If the value of currentfield is less than 1 or greater than maxfields, the value is then currentfield is set to maxfields or 1, respectively. If the TAB key had not been pressed, that means that the subroutine was entered because an edit field was selected by a mouse click, and the current field is set to that field. The subroutine then returns to the line that called it.

If Return (or Enter) is pressed or the OK button is clicked, the variable dialogactive is set to false (0) and the WHILE loop ends.

Note that at no time an express INPUT is made to obtain data from the computer operator. All the operator has to do is enter the information in the edit field boxes in any order of his choice. When the WHILE loop is exited by pressing Return or clicking in the OK button, the information stored in the variable array EDIT$() are transferred to the info$() variable array. Note that this transfer of data must be done before window 2 is closed. When the window closes, the information in the edit fields and EDIT$ will be lost. Note that EDIT$ is never explicitly DIMensioned; DIMensioning is automatically done as the edit fields are created.

Before the subprogram exits and returns to the main program, it closes window 2; PUTs the stored screen data back, thereby restoring window 1; and ERASEs the cursor and rect arrays. Erasing the arrays serves two purposes:

1. It enables them to be reinitialized when the subprogram is next called and

2. It frees the memory used by these arrays so the program can use it for other purposes.

The sub program does seem at first glance to be a bit complex and involved to be a substitute for a series of simple INPUT statements. However, if you were to write an input routine to get a set of data and allow complete editing and error checking of that data, it would be more involved than this routine. This subprogam can be simplified if size and memory are a consideration. The first simplification is be to eliminate the block of programming that changes the shape of the cursor. This block starts with the line “dummy = MOUSE (0)” and ends with the line that ends “ELSE INITCURSOR.” You can then delete all lines that refer to or define the cursor array. The second deletion is the subroutine “tabfield.” If you do that, you must also delete the line that starts “IF status = 2” since this line calls the subroutine. If you delete this routine, the operator can move between edit fields only by means of the mouse. Pressing the Tab key would no longer change the edit fields.

HOW TO USE THE PROGRAM

After you enter the entire program and try it out, delete the main program and keep only the subprogram. Save the subprogram, choosing the TEXT option in the save window. When you are ready to use it, MERGE it into your program. MERGE works only if the merged program has been saved in TEXT format.

Prior to calling the subprogram, your program must set the variable “maxfields” to the number of fields to be input; the number of edit fields and labels are taken from this number. You need then only put in the names of the labels (in the label$ array) and transfer the information from the info$ array to your specific variables. The only other change you must make is to the cursor shape-changing routine if you haven't deleted it and if maxfields is other than 10. You can call the subprogram from different parts of your program, using appropriate values for maxfields and labels.

Using this subprogram in your programs will give you a clean-looking, efficient, error-free input routine and save you programming time.

Program Listing
DEFINT a-z
maxfields = 10 'number of fields to be inputted

DIM label$ (maxfields), info$ (maxfields), corner (4)
DATA Last Name,First Name,MI,Title,Street and      No.,City,ST,ZIP,Phone,Ref 
#: 'field labels
FOR i = 1 TO maxfields: READ label$(i): NEXT

'Create main window

DATA 10,30,501,310: 'Change numbers to re-size windows
FOR i = 1 TO 4: READ corner (i): NEXT
WINDOW 1,"",(corner (1),corner (2))-(corner (3),corner (4)),2 

PRINT "This is the background window in which      the main program runs."
PRINT "It will be covered by the data input  window and restored when"
PRINT "the data input window is closed."

doitagain: inputroutine corner (), maxfields, label$(), info$()

Lname$ = info$(1):Cname$ = info$(2)
MI$ = info$(3):Pre$ = info$(4)
street$ = info$(5):City$ = info$(6)
ST$ = info$(7):ZIP$ = info$(8)
Phone$ = info$(9):REFNUM$ = info$(10)

'Use VAL function to change strings to numbers where necessary

PRINT
IF Pre$ <> "" THEN PRINT Pre$;" ";
PRINT Cname$;" ";
IF MI$ <>"" THEN PRINT MI$;". ";
PRINT Lname$
IF street$ <> "" THEN PRINT street$
IF City$ <> "" THEN PRINT City$; ", ";
IF ST$ <> "" THEN PRINT ST$; "  "; ZIP$
IF Phone$ <> "" THEN PRINT Phone$
IF REFNUM$ <> "" THEN PRINT label$(10);" ";REFNUM$
PRINT:PRINT"Press Return to end or press any other key to try it again."

loop: test$ = INKEY$: IF test$ = "" THEN loop      ELSE IF test$ = CHR$(13) 
THEN END  ELSE doitagain

'Subroutine begins here

SUB inputroutine (corner(), maxfields, label$(),   info$()) STATIC
left = 25: top = 50: right = 480: bottom = 300 'window 2 corners; change 
to re-size window
getleft = left - corner (1) -1: gettop = top - corner (2)      - 1: getright 
= right - corner (1): getbottom =  bottom - corner (2) 'corners of rectangle 
for GET
DIM rect(4+(((getbottom-gettop)+1) * 2 * INT       (((getright-getleft) 
+ 16)/16))), cursor (33)

'Create I-beam cursor

FOR i = 3 TO 12: cursor (i) = &H80: NEXT
cursor (0) = &H630: cursor (15) = cursor (0)
cursor (1) = &H140: cursor (14) = cursor (1)
cursor (2) = &H80: cursor (13) = cursor (2)
FOR i = 16 TO 31: cursor (i) = &H0: NEXT
cursor (32) = &HC
cursor (33) = &H9

GET(getleft,gettop)-(getright,getbottom),rect 'Preserve background 

WINDOW 2,"",(left,top)-(right,bottom),3
CLS
GOSUB refresh 'Window refresh routine
TEXTFONT 1 'setup edit fields with Geneva font

FOR i = maxfields TO 1 STEP -1

    EDIT FIELD i,info$(i),(30+((i-1) MOD 2)  *220,(i+(i MOD 2))*20-15)-(220+((i-1) 
MOD   2)*220,15+(i+(i MOD 2))*20-15)

NEXT
BUTTON 1,1,"OK",(10,230)-(445,250)
WHILE DIALOG (0) <> 0: WEND 'flushes dialog queue    
dialogactive = -1
WHILE dialogactive
     'monitor cursor position and switch cursor shape
    dummy = MOUSE (0): hloc = MOUSE (1): vloc = MOUSE (2)
    IF NOT ((hloc > 30 AND hloc <220) OR (hloc     > 250 AND hloc <470)) 
THEN INITCURSOR

    IF (hloc>30 AND hloc<220) OR (hloc>250   AND hloc<470) THEN IF (vloc>21 
AND   vloc<38) OR (vloc>61 AND vloc<78) OR   (vloc>102 AND vloc<119) 
 OR (vloc>143  AND vloc<160) OR (vloc>183 AND      vloc<200) THEN SETCURSOR 
VARPTR  (cursor (0)) ELSE INITCURSOR

    status = DIALOG (0)
    IF status =1 OR status = 6 THEN dialogactive = 0 'check for OK button 
or RETURN key
    IF status =2 OR status = 7 THEN  GOSUB   tabfield 'Check for click 
in edit field or for TAB  key
    IF status =2 OR status = 7 THEN  GOSUB tabfield 'Check for click 
in edit field or for TAB key
    IF status = 5 THEN GOSUB refresh
WEND
    
FOR i = 1 TO maxfields: info$(i) = EDIT$(i): NEXT

WINDOW CLOSE 2
PUT (getleft,gettop),rect 'restore backgrnd 
ERASE rect, cursor
EXIT SUB

tabfield: 'selects edit field with TAB key or mouse
    shiftkey = (PEEK (379) AND &H1) * 2

    IF status = 7 THEN currentfield = currentfield +1 
 - shiftkey ELSE currentfield = DIALOG(2)
    IF currentfield < 1 THEN currentfield = maxfields
    IF currentfield > maxfields THEN currentfield=1

    EDIT FIELD currentfield
RETURN

refresh: 'redraw window contents
    CLS
    CALL TEXTFONT (0)

    FOR i = 1 TO maxfields
        MOVETO 30+((i-1) MOD 2)*220, (i+(i MOD 2))*20 - 20
        PRINT label$(i);
    NEXT

RETURN
END SUB
 

Community Search:
MacTech Search:

Software Updates via MacUpdate

Things 3.1.3 - Elegant personal task man...
Things is a task management solution that helps to organize your tasks in an elegant and intuitive way. Things combines powerful features with simplicity through the use of tags and its intelligent... Read more
BetterTouchTool 2.292 - Customize Multi-...
BetterTouchTool adds many new, fully customizable gestures to the Magic Mouse, Multi-Touch MacBook trackpad, and Magic Trackpad. These gestures are customizable: Magic Mouse: Pinch in / out (zoom... Read more
Things 3.1.3 - Elegant personal task man...
Things is a task management solution that helps to organize your tasks in an elegant and intuitive way. Things combines powerful features with simplicity through the use of tags and its intelligent... Read more
BetterTouchTool 2.292 - Customize Multi-...
BetterTouchTool adds many new, fully customizable gestures to the Magic Mouse, Multi-Touch MacBook trackpad, and Magic Trackpad. These gestures are customizable: Magic Mouse: Pinch in / out (zoom... Read more
Bookends 12.8.3 - Reference management a...
Bookends is a full-featured bibliography/reference and information-management system for students and professionals. Bookends uses the cloud to sync reference libraries on all the Macs you use.... Read more
Mellel 3.5.5 - The word processor for sc...
Mellel is the leading word processor for OS X and has been widely considered the industry standard since its inception. Mellel focuses on writers and scholars for technical writing and multilingual... Read more
Mellel 3.5.5 - The word processor for sc...
Mellel is the leading word processor for OS X and has been widely considered the industry standard since its inception. Mellel focuses on writers and scholars for technical writing and multilingual... Read more
Bookends 12.8.3 - Reference management a...
Bookends is a full-featured bibliography/reference and information-management system for students and professionals. Bookends uses the cloud to sync reference libraries on all the Macs you use.... Read more
Carbon Copy Cloner 4.1.18 - Easy-to-use...
Carbon Copy Cloner backups are better than ordinary backups. Suppose the unthinkable happens while you're under deadline to finish a project: your Mac is unresponsive and all you hear is an ominous,... Read more
Hopper Disassembler 4.2.14- - Binary dis...
Hopper Disassembler is a binary disassembler, decompiler, and debugger for 32- and 64-bit executables. It will let you disassemble any binary you want, and provide you all the information about its... Read more

Little Red Lie (Games)
Little Red Lie 1.0 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0 (iTunes) Description: ARE YOU MORE AFRAID OF POVERTY THAN DEATH? Little Red Lie is a narrative-focused, interactive fiction experience that reduces... | Read more »
You can now apply to be Clash of Clans...
Earlier this month, word got out that the Builder, the trusty handiman who tirelessly built every single building inevery singleClash of Clansbase had called it quits. Sick of seeing his work destroyed endless, the Builder has set out for our world... | Read more »
Meshi Quest beginner's guide - how...
Meshi Quest is Square Enix's newest free-to-play release, and it's a real charmer. You start off as the head of a sushi restaurant, upgrading your food and equipment as you serve visitors heaping helpings of your delicious meals. As you progress,... | Read more »
BUST-A-MOVE JOURNEY (Games)
BUST-A-MOVE JOURNEY 1.0.0 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0.0 (iTunes) Description: BUST-A-MOVE Features:- Shoot bubbles and match 3 or more bubbles of the same color to make them pop!- Complete your... | Read more »
The best card combos in Clash Royale
Clash Royale is all about building a deck of units that synergise well. To help you get off to a flying start, we've put together a list of unit combinations that are incredibly effective. Looking for some choice 2v2 combos? Check out our guide. [... | Read more »
The best 2v2 card combos in Clash Royale
2v2 is making it's grand return toClash Royalequite soon. 2v2 has quickly become one of the game's most popular gameplay modes, though they still have yet to make it a permanent fixture in the game. 2v2 is exciting and adds some new flavor to... | Read more »
The best games we played this week - Aug...
Another busy week has come to a close. We played a lot of excellent games this week and now it's time to look back and reflect on some our favorites. Here are our picks for the week of August 18. [Read more] | Read more »
War Wings beginner's guide - how to...
War Wings is the newest project from well-established game maker Miniclip. It's a World War II aerial dogfighting game with loads of different airplane models to unlock and battle. The game offers plenty of single player and multiplayer action. We... | Read more »
How to win every 2v2 battle in Clash Roy...
2v2 is coming back to Clash Royale in a big way. Although it's only been available for temporary periods of time, 2v2 has seen a hugely positive fan response, with players clamoring for more team-based gameplay. Soon we'll get yet another taste of... | Read more »
Roll to Win with Game of Dice’s new upda...
Joycity’s hit Game of Dice gets a big new update this week, introducing new maps, mechanics, and even costumes. The update sets players loose on an exciting new map, The Cursed Tower, that allows folks to use special Runes mid-match. If you feel... | Read more »

Price Scanner via MacPrices.net

Free Instant Translator 2.0 App For iOS Relea...
Mobile application development company, Neoappz has announced the release and immediate availability of Instant Translator 2.0 for iOS devices. Instant Translator is a user-friendly application which... Read more
2017 15-inch MacBook Pros on sale for $200 of...
Amazon has 2017 15″ MacBook Pros on sale for $200 off MSRP. Shipping is free: – 15″ 2.8GHz MacBook Pro Space Gray: $2199.99, $200 off MSRP – 15″ 2.8GHz MacBook Pro Silver: $2296, $103 off MSRP – 15″... Read more
Apple’s 2017 Back to School Promotion: Free B...
Purchase a new Mac using Apple’s Education discount, and take up to $300 off MSRP. All teachers, students, and staff of any educational institution qualify for the discount. Shipping is free. As part... Read more
Clearance 2016 12-inch Retina MacBooks, Apple...
Apple has Certified Refurbished 2016 12″ Retina MacBooks available starting at $1019. Apple will include a standard one-year warranty with each MacBook, and shipping is free. The following... Read more
15-inch 2.2GHz Retina MacBook Pro, Apple refu...
Apple has Certified Refurbished 2015 15″ 2.2GHz Retina MacBook Pros available for $1699. That’s $300 off MSRP, and it’s the lowest price available for a 15″ MacBook Pro. An Apple one-year warranty is... Read more
Apple refurbished Mac minis available startin...
Apple has Certified Refurbished Mac minis available starting at $419. Apple’s one-year warranty is included with each mini, and shipping is free: – 1.4GHz Mac mini: $419 $80 off MSRP – 2.6GHz Mac... Read more
Apple refurbished iPad Pros available startin...
Apple has Certified Refurbished 2016 12″ WiFi iPad Pros available starting at $589. An Apple one-year warranty is included with each model, and shipping is free: – 32GB 12″ iPad Pro WiFi: $589... Read more
Weekend sale: 13-inch MacBook Pros for up to...
Amazon has new 2017 13″ MacBook Pros on sale today for up to $200 off MSRP, each including free shipping: – 13″ 3.1GHz/256GB Space Gray MacBook Pro (MPXV2LL/A): $1599.99 $200 off MSRP – 13″ 3.1GHz/... Read more
Back To School With The Edge Desk All-in-one...
Back to school is just around the corner, and the ergonomically correct Edge Desk all-in-one portable kneeling desk is ideal for students living in dorms and small apartments, Edge Desk features:... Read more
Norton Core Secure Wi-Fi Router Now Available...
First introduced at the 2017 Consumer Electronics Show (CES), Norton Core, a secure, high-performance Wi-Fi router, fundamentally changed the concept of Wi-Fi routers by making security the primary... Read more

Jobs Board

*Apple* Retail - Multiple Positions - Apple,...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
Development Operations and Site Reliability E...
Development Operations and Site Reliability Engineer, Apple Payment Gateway Job Number: 57572631 Santa Clara Valley, California, United States Posted: Jul. 27, 2017 Read more
Frameworks Engineering Manager, *Apple* Wat...
Frameworks Engineering Manager, Apple Watch Job Number: 41632321 Santa Clara Valley, California, United States Posted: Jun. 15, 2017 Weekly Hours: 40.00 Job Summary Read more
*Apple* Solutions Consultant - Apple Inc. (U...
…about helping others on a team while also delighting customers? As an Apple Solutions Consultant (ASC), you will discover customers needs and help connect them Read more
*Apple* Solutions Consultant - Apple Inc. (U...
Job Summary As an Apple Solutions Consultant, you'll be the link between our future customers and our products. You'll showcase your entrepreneurial spirit as you Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.