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ABS( n ) Description: This function returns | n | (the absolute value of n). Usage: print abs( -5) produces: 5 print abs( 6 - 13 ) produces: 7 ASC( n$ ) Description: This function returns the ASCII value of the first character of string n$. Usage: print asc( "A" ) produces: 65 let name$ = "Tim" firstLetter = asc(name$) print firstLetter produces: 84 print asc( "" ) produces: 0 ACS( n ) Description: Returns the arc-cosine of the number n. Usage: . . for c = 1 to 45 print "The arc-cosine of "; c; " is "; acs(c) next c . . Note: See also COS( ) ASN( n ) Description: Returns the arcsine of the number n. Usage: . . for c = 1 to 45 print "The arcsine of "; c; " is "; asn(c) next c . . Note: See also SIN( ) ATN( n ) Description: Returns the arc-tangent of the number n. Usage: . . for c = 1 to 45 print "The arctangent of "; c; " is "; atn(c) next c . . Note: See also TAN( ) BEEP Description: This command simply rings the system bell, as in CTRL-G Usage: . . [loop] input "Give me a number between 1 and 10?"; number if number < 1 or number > 10 then beep : print "Out of range!" : goto [loop] print "The square of "; number; " is "; number ^ 2 . . BMPBUTTON #handle, filespec, return, corner, posx, posy Description: This statement lets you add bitmapped buttons to windows that you open. The main program window cannot have buttons added, but any window that you create via the OPEN command can have as many buttons as you want. Usage: Before you actually OPEN the window, each bitmapped button must be declared with a BMPBUTTON statement. Here is a brief description for each parameter as listed above: #handle - You must use the same handle that will be used for the window that the button will belong to. filespec - The full pathname of the *.bmp file containing the bitmap for the button you are creating. The button will be the same size as the bitmap. return - Again, use only one word and do not bound it with quotes or use a string variable. If return is set to a valid branch label, then when the button is pressed, execution will restart there (just as with GOTO or GOSUB), but if return is not a valid branch label, then the value of return is used as input to a specified variable (as in input a$). corner - UL, UR, LL, or LR specifies which corner of the window to anchor the button to. For example, if LR is used, then the button will appear in the lower right corner. UL = upper left, UR = upper right, LL = lower left, and LR = lower right posx, posy - These two parameters determine how to place the button relative to the corner it has been anchored to. For example if corner is LR, posx is 5, and posy is 5, then the button will be 5 pixels up and left of the lower right corner. Another way to use posx & posy is to use values less than one. For example, if corner is UL, posx is .9, and posy is .9, then the button will be positioned 9/10th of the distance of the window in both x and y from the upper left corner (and thus appear to be anchored to the lower right corner). A collection of button *.bmp has been included with Liberty BASIC, including blanks. Windows Paint can be used to edit and make buttons for Liberty BASIC. Program execution must be halted at an input statement in order for a button press to be read and acted upon. See also: BUTTON, MENU BUTTON #handle, label, return, corner, posx, posy Description: This statement lets you add buttons to windows that you open. The main program window cannot have buttons added, but any window that you create via the OPEN command can have as many buttons as you want. Usage: Before you actually OPEN the window, each button must be declared with a BUTTON statement. Here is a brief description for each parameter as listed above: #handle - You must use the same handle that will be used for the window that the button will belong to. label - Type the label desired for the button here. Do not bound the word with quotes, and do not use a string variable. return - Again, use only one word and do not bound it with quotes or use a string variable. If return is set to a valid branch label, then when the button is pressed, execution will restart there (just as with GOTO or GOSUB), but if return is not a valid branch label, then the value of return is used as input to a specified variable (as in input a$). corner - UL, UR, LL, or LR specifies which corner of the window to anchor the button to. For example, if LR is used, then the button will appear in the lower right corner. UL = upper left, UR = upper right, LL = lower left, and LR = lower right posx, posy - These two parameters determine how to place the button relative to the corner it has been anchored to. For example if corner is LR, posx is 5, and posy is 5, then the button will be 5 pixels up and left of the lower right corner. Another way to use posx & posy is to use values less than one. For example, if corner is UL, posx is .9, and posy is .9, then the button will be positioned 9/10th of the distance of the window in both x and y from the upper left corner (and thus appear to be anchored to the lower right corner). Program execution must be halted at an input statement in order for a button press to be read and acted upon. See below. BUTTON Continued Here is a sample program: ' this button will be labeled Sample and will be located ' in the lower right corner. When it is pressed, program ' execution will transfer to [test] button #graph, Bell, [bell], LR, 5, 5 ' this button will be labeled Example and will be located ' in the lower left corner. When it is pressed, the string ' "Example" will be returned. button #graph, Quit, [quit], LL, 5, 5 ' open a window for graphics open "Button Sample" for graphics as #graph ' print a message in the window print #graph, "\\This is a test" print #graph, "flush" ' get button input [loop] input b$ ' stop and wait for a button to be pressed if b$ = "Example" then [example] goto [loop] ' the Sample button has been pressed, ring the terminal bell ' and close the window [bell] beep close #graph end ' The Example button has been pressed, close the window ' without ringing the bell [quit] close #graph end See also: BMPBUTTON, MENU CHR$( n ) Description: Returns a one character long string, consisting of the character represented on the ASCII table by the value n (0 - 255). Usage: ' print each seperate word in text$ on its own line text$ = "now is the time for all great men to rise" for index = 1 to len(text$) c$ = mid$(text$, index, 1) ' if c$ is a space, change it to a carraige return if c$ = chr$(32) then c$ = chr$(13) print c$ ; next index Produces: now is the time for all great men to rise CLOSE #handle Description: This command is used to close files and devices. This is the last step of a file read and/or write, or to close graphic, spreadsheet, or other windows when finished with them. If when execution of a program is complete there are any files or devices left open, Liberty BASIC will display a dialog informing you that it found it necessary to close the opened files or devices. This is designed as an aid for you so that you will be able to correct the problem. If on the other hand you choose to terminate the program early (this is done by closing the program's main window before the program finishes), then Liberty BASIC will close any open files or devices without posting a notice to that effect. Usage: open "Graphic" for graphics as #gWindow ' open a graphics window print #gWindow, "home" ' center the pen print #gWindow, "down" ' put the pen down for index = 1 to 100 ' loop 100 times print #gWindow, "go "; index ' move the pen foreward print #gWindow, "turn 63" ' turn 63 degrees next index input "Press 'Return'."; r$ ' this appears in main window close #gWindow ' close graphic window CLS Description: Clears the main program window of text and sets the cursor back at the upper left hand corner. Useful for providing a break to seperate different sections of a program functionally. Additionally, since the main window doesn't actually discard past information on its own, the CLS command can be used to reclaim memory from your program by forcing the main window to dump old text. Usage: . . print "The total is: "; grandTotal input "Press 'Return' to continue."; r$ cls print "*** Enter Next Round of Figures ***" . . CONFIRM string; responseVar Description: This statement opens a dialog box displaying the contents of string and presenting two buttons marked 'Yes' and 'No'. When the selection is made, the string "yes" is returned if 'Yes' is pressed, and the string "no" is returned if 'No' is pressed. The result is placed in responseVar. Usage: [quit] ' bring up a confirmation box to be sure that ' the user wants to quit confirm "Are you sure you want to QUIT?"; answer$ if answer$ = "no" then [mainLoop] end COS( n ) Description: Returns the cosine of the number n. Usage: . . for c = 1 to 45 print "The cosine of "; c; " is "; cos(c) next c . . Note: See also SIN( ) and TAN( ) DATE$( ) Description: Instead of adopting MBASIC's date$ variable, we decided to use a function instead, figuring that this might give us additional flexibility later. This function returns the current date in long format. Usage: print date$( ) Produces: Feb 5, 1991 Or you can assign a variable the result: d$ = date$( ) DIM array(size, size) Description: DIM sets the maximum size of an array. Any array can be dimensioned to have as many elements as memory allows. If an array is not DIMensioned explicitly, then the array will be limited to 10 elements, 0 to 9. Non DIMensioned double subscript arrays will be limited to 100 elements 0 to 9 by 0 to 9. Usage: print "Please enter 10 names." for index = 0 to 9 input names$ : name$(index) = name$ next index The FOR . . . NEXT loop in this example is limited to a maximum value of 9 because the array names$( ) is not dimensioned, and therefore is limited to 10 elements. To remedy this problem, we can add a DIM statement, like so: dim names$(20) print "Please enter 20 names." for index = 0 to 19 input names$ : names$(index) = name$ next index Double subscripted arrays can store information more flexibly, like so: dim customerInfo$(10, 5) print "Please enter information for 10 customers." for index = 0 to 9 input "Customer name >"; info$ : customerInfo$(index, 0) = info$ input "Address >"; info$ : customerInfo$(index, 1) = info$ input "City >"; info$ : customerInfo$(index, 2) = info$ input "State >"; info$ : customerInfo$(index, 3) = info$ input "Zip >"; info$ : customerInfo$(index, 4) = info$ next index ELSE See IF . . . THEN . . . ELSE EOF(#handle) Description: Used to determine when reading from a sequential file whether the end of the file has been reached. If so, -1 is returned, otherwise 0 is returned. Usage: open "testfile" for input as #1 if eof(#1) < 0 then [skipIt] [loop] input #1, text$ print text$ if eof(#1) = 0 then [loop] [skipIt] close #1 END Description: Used to immediately terminate execution of a program. If any files or devices are still open (see CLOSE) when execution is terminated, then Liberty BASIC will close them for you and present you with a dialog expressing this fact. It is good programming practice to close files and devices before terminating execution. Note: The STOP statement is functionally identical to END and is interchangable Usage: . . print "Preliminary Tests Complete." [askAgain] input "Would you like to continue (Y/N) ?"; yesOrNo$ yesOrNo$ = left$(yesOrNo$, 1) if yesOrNo$ = "y" or yesOrNo$ = "Y" then [continueA] ifYesOrNo$ = 'n" or yesOrNo$ = "N" then end print "Please answer Y or N." goto [askAgain] [continueA] . . EXP( n ) Description: This function returns e ^ n, e being 2.7182818 . . . Usage: print exp( 5 ) produces: 148.41315 FIELD #handle, # as varName, # as varName, . . . Description: FIELD is used with an OPEN "filename.ext" for random as #handle statement to specify the fields of data in each record of the opened file. For example in this program FIELD sets up 6 fields of data, each with an appropriate length, and associates each with a string variable that holds the data to be stored in that field: open "custdata.001" for random as #cust len = 70 ' open a random access file field #cust, 20 as name$, 20 as street$, 15 as city$, 2 as state$, 10 as zip$, 3 as age [inputLoop] input "Name >"; name$ input "Street >"; street$ input "City >"; city$ input "State >"; state$ input "Zip Code >"; zip$ input "Age >"; age confirm "Is this entry correct?"; yesNo$ ' ask if the data is entered correctly if yesNo$ = "no" then [inputLoop] recNumber = recNumber + 1 ' add 1 to the record # and put the record put #cust, recNumber confirm "Enter more records?"; yesNo$ ' ask whether to enter more records if yesNo$ = "yes" then [inputLoop] close #cust ' end of program, close file end Notice that Liberty BASIC permits the use of numeric variables in FIELD (eg. age), and it allows you to PUT and GET with both string and numeric variables, automatically, without needing LSET, RSET, MKI$, MKS$, MKD$, CVI, CVS, & CVD that are required with Microsoft BASICs. Note: See also PUT and GET FILEDIALOG titleString, templateString, receiverVar$ Description: This command opens a file dialog box. The titleString is used to label the dialog box. The templateString is used as a filter to list only files matching a wildcard, or to place a full suggested filename. The box lets you navigate around the directory structure, looking at files that have a specific extension. You can then select one, and the resulting full path specification will be placed into receiverVar$, above. The following example would produce the dialog box below: filedialog "test it", "*.txt", fileName$ If then summary.txt were selected, and OK clicked, then program execution would resume after placing the string "c:\liberty\summary.txt" into fileName$. If on the other hand Cancel were clicked, then an empty string would be placed into fileName$. Program execution would then resume. Look at the program grapher1.bas for a practical application of this command. FOR . . . NEXT Description: The FOR . . . NEXT looping construct provides a way to repeatedly execute code a specific amount of times. A starting and ending value are specified like so: for var = 1 to 10 {BASIC code} next var In this case, the {BASIC code} is executed 10 times, with var being 1 the first time, 2 the second, and on through 10 the tenth time. Optionally (and usually) var is used in some calculation(s) in the {BASIC code}. For example if the {BASIC code} is print var ^ 2, then a list of squares for var will be displayed upon execution. The specified range could just as easily be 2 TO 20, instead of 1 TO 10, but since the loop always counts +1 at a time, the first number must be less than the second. The way around this limitation is to place STEP n at the end of for FOR statement like so: for index = 20 to 2 step -1 {BASIC code} next index This would loop 19 times returning values for index that start with 20 and end with 2. STEP can be used with both positive and and negative numbers and it is not limited to integer values. For example: for x = 0 to 1 step .01 print "The sine of "; x; " is "; sin(x) next x Note: It is not recommended to pass control of a program out of a FOR . . . NEXT loop using GOTO (GOSUB is acceptable). Liberty BASIC may behave unpredictably. For example: for index = 1 to 10 print "Enter Customer # "; index input customer$ if customer$ = "" then [quitEntry] ' <- it isn't allowed to cut out of a for ... next loop like this cust$(index) = customer$ next index [quitEntry] . . . is not allowed! Rather use while ... wend: index = 1 while customer$ <> "" and index <= 10 print "Enter Customer # "; index input customer$ cust$(index) = customer$ index = index + 1 wend GET #handle, recordNumber Description: GET is used after a random access file is opened to get a record of information (see FIELD) out of the file from a specified position. For example: open "custdata.001" for random as #cust len = 70 ' open random access file field #cust, 20 as name$, 20 as street$, 15 as city$, 2 as state$, 10 as zip$, 3 as age ' get the data from record 1 get #cust, 1 print name$ print street$ print city$ print state$ print zip$ print age close #cust end Note: See also PUT, FIELD GETTRIM #handle, recordNumber Description: The GETTRIM command is exactly like the GET command, but when data is retrieved, all leading and trailing blank space is removed from all data fields before being committed to variables. GOSUB label Description: GOSUB causes execution to proceed to the program code following the label if it exists, using the form 'GOSUB label'. The label can be either a traditional line number or a branch label in the format [???????] where the ?'s can be any upper/lowercase letter combination. Spaces and numbers are not allowed. Here are some valid branch labels: [mainMenu] [enterLimits] [repeatHere] Here are some invalid branch labels: [enter limits] mainMenu [1moreTime] After execution is transferred to the point of the branch label, then each statement will be executed in normal fashion until a RETURN is encountered. When this happens, execution is transferred back to the statement immediately after the GOSUB. The section of code between a GOSUB and its RETURN is known as a 'subroutine.' One purpose of a subroutine is to save memory by having only one copy of code that is used many times throughout a program. Usage: . . print "Do you want to continue?" gosub [yesOrNo] if answer$ = "N" then [quit] print "Would you like to repeat the last sequence?" gosub [yesOrNo] if answer$ = "Y" then [repeat] goto [generateNew] [yesOrNo] input answer$ answer$ = left$(answer$, 1) if answer$ = "y" then answer$ = "Y" if answer$ = "n" then answer$ = "N" if answer$ = "Y" or answer$ = "N" then return print "Please answer Y or N." goto [yesOrNo] . . You can see how using GOSUB [yesOrNo] in this case saves many lines of code in this example. The subroutine [yesOrNo] could easily be used many other times in such a hypothetical program, saving memory and reducing typing time and effort. This reduces errors and increases productivity. See also GOTO GOTO label Description: GOTO causes Liberty BASIC to proceed to the program code following the label if one exists, using the form 'GOTO label'. The label can be either a traditional line number or a branch label in the format [???????] where the ?'s can be any upper/lowercase letter combination. Spaces and digits are not allowed. Here are some valid branch labels: [mainMenu] [enterLimits] [repeatHere] Here are some invalid branch labels: [enter limits] mainMenu [1moreTime] Usage: . . [repeat] . . [askAgain] print "Make your selection (m, r, x)." input selection$ if selection$ = "M" then goto [menu] if selection$ = "R" then goto [repeat] if selection$ = "X" then goto [exit] goto [askAgain] . . [menu] print "Here is the main menu." . . [exit] print "Okay, bye." end Notes: In the lines containing IF . . . THEN GOTO, the GOTO is optional. The expression IF . . . THEN [menu] is just as valid as IF . . . THEN GOTO [menu]. But in the line GOTO [askAgain], the GOTO is required. See also GOSUB IF expression THEN expression(s) Description: The purpose of IF . . . THEN is to provide a mechanism for your computer software to make decisions based on the data available. A decision-making mechanism is used in very simple situations and can be used in combinations to engineer solutions to problems of great complexity. The expression (see above) is a boolean expression (meaning that it evaluates to a true or false condition). In this expression we place the logic of our decision-making process. For example, if we are writing a inventory application, and we need to know when any item drops below a certain level in inventory, then our decision-making logic might look like this: . . if level <= reorderLevel then expression(s) next BASIC program line . . The 'level <= reorderLevel' part of the above expression will evaluate to either true or false. If the result was true, then the expression(s) part of that line (consisting of a branch label or any valid BASIC statements) will be executed. Otherwise execution will immediately begin at the next BASIC program line. The following are permitted: if a < b then [lessThan] This causes program execution to begin at branch label [lessThan] if a is less than b. if sample < lowLimit or sample > highLimit then beep : print"Out of range!" This causes the terminal bell to ring and the message Out of range! to be displayed if sample is less than lowLimit or greater then highLimit. IF expression THEN expression(s)1 ELSE expression(s)2 Description: This extended form of IF . . . THEN adds expressiveness and simplifies coding of some logical decision-making software. Here is an example of its usefulness. Consider: [retry] input"Please choose mode, (N)ovice or e(X)pert?"; mode$ if len(mode$) = 0 then print "Invalid entry! Retry" : goto [retry] mode$ = left$(mode$, 1) if instr("NnXx", mode$) = 0 then print "Invalid entry! Retry" : goto [retry] if instr("Nn", mode$) > 0 then print "Novice mode" : goto [main] print "eXpert mode" [main] print "Main Selection Menu" Look at the two lines before the [main] branch label. The first of these two lines is required to branch over the next line. These lines can be shortened to one line as follows: if instr("Nn",mode$)> 0 then print "Novice mode" else print "eXpert mode" Some permitted forms are as follows: if a < b then statement else statement if a < b then [label] else statement if a < b then statement else [label] if a < b then statement : statement else statement if a < b then statement else statement : statement if a < b then statement : goto [label] else statement if a < b then gosub [label1] else gosub [label2] Any number of variations on these formats are permissible. The a < b boolean expression is of course only a simple example chosen for convenience. You must replace it with the correct expression to suit your problem. INPUT #handle "string expression"; variableName Description: This command has three possible forms: input var - stop and wait for user to enter data in the program's main window and press the 'Return' key, then assign the data entered to var. input "enter data"; var - display the string "enter data" and then stop and wait for user to enter data in the program's main window and press 'Return', then assign the data entered to var. input #name, var - or - input #name, var1, var2 - Get the next data item from the open file or device using handle named #handle and assign the data to var. If no device or file exists that uses the handle named #handle, then return an error. In the second case, the next two data items are fetched and assigned to var1 and var2. Usage: 'Display a text file input "Please type a filename >"; filename$ open filename$ for input as #text [loop] if eof(#text) <> 0 then [quit] input #text, item$ print item$ goto [loop] [quit] close #text print "Done." end Note: In Liberty BASIC release 1.0, INPUT cannot be used to input data directly into arrays, only into the simpler variables. input a$(1) - is illegal input string$ : a$(1) = string$ - use this instead This shortcoming will be addressed in a future release. This should not be a problem anyway if you will be checking the input for validity before ultimately accepting it. INPUT (continued) Most versions of Microsoft BASIC implement INPUT to automatically place a question mark on the display in front of the cursor when the user is prompted for information like so: input "Please enter the upper limit"; limit produces: Please enter the upper limit ? | Liberty BASIC permits you the luxury of deciding for yourself whether the question mark appears at all. input "Please enter the upper limit :"; limit produces: Please enter the upper limit: | and: input limit produces simply: ? | In the simple form input limit, the question mark is inserted automatically, but if you do specify a prompt, as in the above example, only the contents of the prompt are displayed, and nothing more. If for some reason you wish to input without a prompt and without a question mark, then the following will achieve the desired effect: input ""; limit Additionally, in most Microsoft BASICs, if INPUT expects a numeric value and a non numeric or string value is entered, the user will be faced with a comment something like 'Redo From Start', and be expected to reenter. Liberty BASIC does not automatically do this, but converts the entry to a zero value and sets the variable accordingly. This is not considered a problem but rather a language feature, allowing you to decide for yourself how your program will respond to the situation. One last note: In Liberty BASIC input prompt$; limit is also valid. Try: prompt$ = "Please enter the upper limit:" input prompt$; limit INPUT$(#handle, items) Description: Permits the retrieval of a specified number of items from an open file or device using #handle. If #handle does not refer to an open file or device then an error will be reported. Usage: 'read and display a file one character at a time open "c:\autoexec.bat" for input as #1 [loop] if eof(#1) <> 0 then [quit] print input$(#1, 1); goto [loop] [quit] close #1 end For most devices (unlike disk files), one item does not refer a single character, but INPUT$( ) may return items more than one character in length. In most cases, use of INPUT #handle, varName works just as well or better for reading devices. INSTR(string1, string2, starting) Description: This function returns the position of string2 within string1. If string2 occurs more than once in string 1, then only the position of the leftmost occurance will be returned. If starting is included, then the search for string2 will begin at the position specified by starting. Usage: print instr("hello there", "lo") produces: 4 print instr("greetings and meetings", "eetin") produces: 3 print instr("greetings and meetings", "eetin", 5) produces: 16 If string2 is not found in string1, or if string2 is not found after starting, then INSTR( ) will return 0. print instr("hello", "el", 3) produces: 0 and so does: print instr("hello", "bye") INT(number) Description: This function removes the fractional part of number, leaving only the whole number part behind. Usage: [retry] input "Enter an integer number>"; i if i<>int(i) then bell: print i; " isn't an integer! Re-enter.": goto [retry] LEFT$(string, number) Description: This function returns from string the specified number of characters starting from the left. So if string is "hello there", and number is 5, then "hello" would be the result. Usage: [retry] input "Please enter a sentence>"; sentence$ if sentence$ = "" then [retry] for i = 1 to len(sentence$) print left$(sentence$, i) next i Produces: Please enter a sentence>That's all folks! T Th Tha That That' That's That's_ That's a That's al That's all That's all_ That's all f That's all fo That's all fol That's all folk That's all folks That's all folks! Note: If number is zero or less, then "" (an empty string) will be returned. If the number is greater than or equal to the number of characters in string, then string will be returned. See also MID$( ) and RIGHT$( ) LEN( string ) Description: This function returns the length in characters of string, which can be any valid string expression. Usage: prompt "What is your name?"; yourName$ print "Your name is "; len(yourName$); " letters long" LET assignment expression Description: LET is an optional prefix for any BASIC assignment expression. Most do leave the word out of their programs, but some prefer to use it. Usage: Either is acceptable: let name$ = "John" or name$ = "John" Or yet again: let c = sqr(a^2 + b^2) or c = sqr(a^2 + b^2) LOG( n ) Description: This function returns the natural log of n. Usage: print log( 7 ) produces: 1.9459101 MENU #handle, title, text, branchLabel, text, branchLabel, | , . . . Description: Adds a pull down menu to the window at #handle. Title specifies the title of the menu, as seen on the menu bar of the window, and each text, branchLabel pair after the title adds a menu item to the menu, and tells Liberty BASIC where to branch to when the menu item is chosen. The | character can optionally be placed between menu items, to cause a seperating line to be added between the items with the menu is pulled down. As an example, if you wanted to have a graphics window opened, and then be able to pull down some menus to control color and geometric objects, your opening code might look like this: menu #geo, &Colors, &Red, [setRed], &Green, [setGreen], &Blue, [setBlue] menu #geo, &Shapes, &Rectangle, [asRect], &Triangle, [asCircle], &Line, [asLine] open "Geometric wite-board" for graphics_nsb as #geo input r$ ' stop and wait for a menu item to be chosen Notice that the MENU lines must go before the OPEN statement, and must use the same handle as the window that it will be associated with (#geo in this case). This is the same with the BUTTON statement (see BUTTON). See that execution must be stopped at an input statement for the menu choice to be acted upon. This is also the same as with BUTTON. Also notice that the & character placed in the title and text items for the menu determines the accelerator placement for each menu. Try experimenting. MID$(string, index, number) Description: Permits the extraction of a sequence of characters from string starting at index. If number is not specified, then all the characters from index to the end of the string are returned. If number is specified, then only as many characters as number specifies will be returned, starting from index. Usage: print mid$("greeting Earth creature", 10, 5) Produces: Earth And: string = "The quick brown fox jumped over the lazy dog" for i = 1 to len(string$) step 5 print mid$(string$, i, 5) next i Produces: The_q uick_ brown _fox_ jumpe d_ove r_the _lazy _dog Note: See also LEFT$( ) and RIGHT$( ) NEXT var see FOR . . . NEXT NOMAINWIN Description: This command instructs Liberty BASIC not to open a main window for the program that includes this statement. Some simple programs which do not use seperate windows for graphics, spreadsheet, or text may use only the main window. Other programs may not need the main window to do their thing, and so simply including NOMAINWIN somewhere in your program source will prevent the window from opening. If NOMAINWIN is used, when all other windows owned by that program are closed, then the program terminates execution automatically. For examples of the usage of NOMAINWIN, examine the included Liberty BASIC programs (buttons1.bas for example). NOTICE "string expression" Description: This command pops up a dialog box which displays "string expression" and which has a button OK which the user presses after the message is read. Pressing Enter also closes the dialog box. Two forms are allowed. If "string expression" has no Cr character (ASCII 13), then the title of the dialog box will be 'Notice' and "string expression" will be the message displayed inside the dialog box. If "string expression" does have a Cr character, then the part of "string expression" before Cr will be used as the title for the dialog box, and the part of "string expression" after Cr will be displayed as the message inside. Usage: notice "Super Stats is Copyright 1992, Mathware" Or: notice "Fatal Error!" + chr$(13) + "The entry buffer is full!" OPEN string FOR purpose AS #handle {LEN = #} Description: This statement has many functions. It can be used to open disk files, or to open windows of several kinds. Using OPEN with Disk files: A typical OPEN used in disk I/O looks like this: OPEN "\autoexec.bat" for input as #read This example illustrates how we would open the autoexec.bat file for reading. As you can see, string in this case is "\autoexec.bat", purpose is input, and #handle is read. string - this must be a valid pathname. If the file does not exist, it will be created. purpose - must be input, output, or random #handle - use a unique descriptive word, but must start with a #. This special handle is used to identify the open file in later program statements LEN = # - this is an optional addition for use only when opening a random access file. The # determines how many characters long each record in the file is. If this is not specified, the default length is 128 characters. See FIELD, GET, and PUT. Using OPEN with windows: A typical OPEN used in windows looks like this: OPEN "Customer Statistics Chart" for graphics as #csc This example illustrates how we would open a window for graphics. Once the window is open, there are a wide range of commands that can be given to it. As you can see, string in this case is "Customer Statistics Chart", which is used as the title of the window, purpose is graphics (open a window for graphics), and the #handle is #csc (derived from Customer Statistics Chart), which will be used as an identifier when sending commands to the window. string - can be any valid BASIC string. used to label the window purpose - there are a several of possibilities here: graphics, spreadsheet, text any of these can end in _fs, _nsbars (or other suffixes) #handle - as above, must be a unique, descriptive word starting with # Note: Any opened file or window must be closed before program execution is finished. See CLOSE PRINT #handle, pression ; expression(s) ; Description: This statement is used to send data to the main window, to a disk file, or to other windows. A series of expressions can follow PRINT (there does not need to be any expression at all), each seperated by a semicolon. Each expression is displayed in sequence. If the data is being sent to a disk file, or to a window, then #handle must be present. PRINTing to a the main window: When the expressions are displayed, then the cursor (that blinking vertical bar | ) will move down to the next line, and the next time information is sent to the window, it will be placed on the next line down. If you do not want the cursor to move immediately to the next line, then add an additional semicolor to the end of the list of expressions. This prevents the cursor from being moved down a line when the expressions are displayed. The next time data is displayed, it will be added onto the end of the line of data displayed previously. Usage: Produces: print "hello world" hello world print "hello "; hello world print "world" age = 23 print "Ed is "; age; " years old" Ed is 23 years old When sending to a disk file and in regard to the use of the semicolon at the end of the expression list, the rules are similar (only you don't see it happen on the screen). When printing to a window, the expressions sent are usually commands to the window (or requests for information from the window). For more information, see chapter ?, Liberty BASIC Graphics. PROMPT string; responseVar Description: The PROMPT statement opens a dialog box, displays string, and waits for the user to type a response and press 'Return' (or press the OK or Cancel button). The entered information is placed in responseVar. If Cancel is pressed, then a string of zero length is returned. If responseVar is set to some string value before PROMPT is executed, then that value will become the 'default' or suggested response. This means that when the dialog is opened, the contents of responseVar will already be entered as a response for the user, who then has the option to either type over that 'default' response, or to press 'Return' and accept it. Usage: . . response$ = "C:" prompt "Search on which Drive? A:, B:, or C:"; response$ [testResponse] if response$ = "" then [cancelSearch] if len(response$) = 2 and instr("A:B:C:", response$) > 0 then [search] prompt "Unacceptable response. Please try again. A:, B:, or C:"; again$ goto [testResponse] [search] print "Starting search . . . " . . PUT #handle, recordNumber Description: PUT is used after a random access file is opened to place a record of information (see FIELD) into the file at a specified position. For example: open "custdata.001" for random as #cust len = 70 ' open a random access file field #cust, 20 as name$, 20 as street$, 15 as city$, 2 as state$, 10 as zip$, 3 as age ' enter data into customer variables input name$ . . ' put the data into record 1 put #cust, 1 close #cust end Note: See also GET, FIELD REM comment Description: The REM statement is used to place comments inside of code to clearly explain the purpose of each section of code. This is useful to both the programmer who writes the code or to anyone who might later need to modify the program. Use REM statements liberally. There is a shorthand way of using REM, which is to use the ' (apostrophe) character in place of the word REM. This is cleaner to look at, but use whichever you prefer. Unlike other BASIC statements, with REM you cannot add another statement after it on the same line using a colon ( : ) to seperate the statements. The rest of the line becomes part of the REM statement. Usage: rem let's pretend that this is a comment for the next line print "The mean average is "; meanAverage Or: ' let's pretend that this is a comment for the next line print "The strength of the quake was "; magnitude This doesn't work: rem thank the user : print "Thank you for using Super Stats!" (even the print statement becomes part of the REM statement) Note: When using ' instead of REM at the end of a line, the statement seperator : is not required to seperate the statement on that line from its comment. For example: print "Total dollar value: "; dollarValue : rem print the dollar value Can also be stated: print "Total dollar value: "; dollarValue ' print the dollar value Notice that the : is not required in the second form. RETURN See GOSUB RIGHT$(string, number) Description: Returns a sequence of characters from the right hand side of string using number to determine how many characters to return. If number is 0, then "" (an empty string) is returned. If number is greater than or equal to the number of characters in string, then string will itself be returned. Usage: print right$("I'm right handed", 12) Produces: right handed And: print right$("hello world", 50) Produces: hello world Note: See also LEFT$( ) and MID$( ) RND(number) Description: This function returns a pseudo random number between 0 and 1. This can be useful in writing games and some simulations. The particular formula used in this release might more accurately be called an arbitrary number generator (instead of random number generator), since if a distribution curve of the output of this function were plotted, the results would be quite uneven. Nevertheless, this function should prove more than adequate (especially for game play). In MBASIC it makes a difference what the value of parameter number is, but in Liberty BASIC, it makes no difference. The function will always return an arbitrary number between 0 and 1. Usage: ' print ten numbers between one and ten for a = 1 to 10 print int(rnd(1)*10) + 1 next a SIN(number) Description: This function return the sine of number. Usage: . . for t = 1 to 45 print "The sine of "; t; " is "; sin(t) next t . . Note: See also COS( ) and TAN( ) STR$(numericExpression) Description: This function returns a string expressing the result of numericExpression. In MBASIC, this function would always return a string representation of the expression and it would add a space in front of that string. For example in MBASIC: print len(str$(3.14)) Would produce the number 5 (a space followed by 3.14 for a total of 5 characters). Liberty BASIC leaves it to you to decide whether you want that space or not. If you don't want it, then you need not do anything at all, and if you do want it, then this expression will produce the same result under Liberty BASIC: print len(" " + str$(3.14)) Usage: . . [kids] ' use str$( ) to validate entry input "How many children do you have?"; qtyKids qtyKids$ = str$(qtyKids) ' if the entry contains a decimal point, then the response is no good if instr(qtyKids$, ".") > 0 then print "Bad response. Reenter." : goto [kids] . . TAN(number) Description: This function return the tangent of number. Usage: . . for t = 1 to 45 print "The tangent of "; t; " is "; tan(t) next t . . Note: See also SIN( ) and COS( ) TIME$( ) Description: This function returns a string representing the current time of the system clock in 24 hour format. This function replaces the time$ variable used in MBASIC. See also DATE$( ). Usage: . . ' display the opening screen print "Main selection screen Time now: "; time$( ) print print "1. Add new record" print "2. Modify existing record" print "3. Delete record" . . TRACE number Description: This statement sets the trace level for its application program. This is only effective if the program is run using the Debug menu selection (instead of RUN). If Run is used, then any TRACE statements are ignored by the interpreter. There are three trace levels: 0, 1, and 2. Here are the effects of these levels: 0 = single step mode or STEP 1 = animated trace or WALK 2 = full speed no trace or RUN When any Liberty BASIC program first starts under Debug mode, the trace level is always initially 0. You can then click on any of the three buttons (STEP, WALK, RUN) to determine what mode to continue in. When a TRACE statement is encountered, the trace level is set accordingly, but you can recover from this new trace level by clicking again on the desired button. If you are having trouble debugging code at a certain spot, then you can add a TRACE statement (usually level 0) just before that location, run in Debug mode and then click on RUN. When the TRACE statement is reached, then the debugger will kick in at that point. Usage: . . 'Here is the trouble spot trace 0 ' kick down to single step mode for index = 1 to int(100*sin(index)) print #graph, "go "; index ; " "; int(100*cos(index)) next index . . TRIM$(stringExpression) Description: This function removes any spaces from the start and end of the string in stringExpression. This can be useful for cleaning up data entry among other things. Usage: sentence$ = " Greetings " print len(trim$(sentence$)) Produces: 9 USING(templateString, numericExpression) Description: This function formats numericExpression as a string using templateString. The rules for the format are like those in MBASIC's PRINT USING statement, but since USING( ) is a function, it can be used as part of a larger BASIC expression instead of being useful only for output directly. Usage: ' print a column of ten justified numbers for a = 1 to 10 print using("####.##", rnd(1)*1000) next a VAL(stringExpression) Description: This function returns a numeric value for stringExpression is stringExpression represents a valid numeric value or if it starts out as one. If not, then zero is returned. This function lets your program take string input from the user and carefully analyze it before turning it into a numeric value if and when appropriate. Usage: print 2 * val("3.14") Produces: 6.28 print val("hello") Produces: 0 print val("3 blind mice") Produces: 3 WHILE expression . . . WEND Description: These two statements comprise the start and end of a control loop. Between the WHILE and WEND statements place code (optionally) that will be executed repeatedly while expression evaluates the same. The code between WHILE and WEND will always execute at least once. Once execution reaches the WEND statement, for as long as the WHILE expression evaluates to true, then execution will jump back to the WHILE statement. Expression can be a boolean, numeric, or string expression. Usage: ' loop until midnight (go read a good book) while time$ <> "00:00:00" ' some action performing code might be placed here wend Or: ' loop until a valid response is solicited while val(age$) = 0 input "How old are you?"; age$ if val(age$) = 0 then print "Invalid response. Try again." wend Or: ' generate a list of ten non-consecutive random numbers for count = 1 to 10 while random : random = int(rnd(1)*10)+1 : wend print random next count WORD$( stringExpression, n ) Description: This function returns the nth word in stringExpression. The leading and trailing spaces are stripped from stringExpression and then it is broken down into 'words' at the remaining spaces inside. If n is less than 1 or greater than the number of words in stringExpression, then "" is returned. Usage: print word$("The quick brown fox jumped over the lazy dog", 5) Produces: jumped And: ' display each word of sentence$ on its own line sentence$ = "and many miles to go before I sleep." token$ = "?" while token$ <> "" index = index + 1 tokens$ = word$(sentence$, index) print token$ wend Produces: and many miles to go before I sleep.