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┌────────────────────────────────────────────────────────────────────┐ │ │ │ │ │ AT&T PC6300 SUPPORT BBS - Bulletin Service │ │ │ │ SUBJECT: GW-BASIC Notes for the PC6300 │ │ PROVIDED BY: AT&T PC-Hotline │ │ │ ├────────────────────────────────────────────────────────────────────┤ │ │ │ DIFFERENCES BETWEEN IBM BASIC VERSION 1.1 AND GW-BASIC │ │ │ ├────────────────────────────────────────────────────────────────────┤ │ │ │ 1) IBM COMPATABILITY PACKAGE MODIFICATIONS │ │ │ │ 1.1) RESERVED WORDS AND TOKENS │ │ The reserved words and tokens were incompatable, │ │ making exchange of binary and protected program │ │ files impossible. GW-Basic token values have been │ │ modified by this modification package. │ │ │ │ 1.2) LINE PRINTER AND KEYBOARD OPEN MODE │ │ IBM Basic allows these devices to be open without │ │ a mode specification. GW-Basic would interpret │ │ these cases as open for random and declare a mode │ │ error. │ │ │ │ 1.3) RS232 SUPPORT │ │ The /C switch on the IBM Basic command line allows │ │ the user to specify the sieze of communications │ │ buffers. This feature has been added to all │ │ versions of Basic. │ │ │ │ 1.4) CLEAR Processing │ │ CLEAR should turn off music, reset music to │ │ foreground, turn off PEN and STRIG, and reset DRAW │ │ scale color. Similar processing should happen for │ │ LOAD, RUN, CHAIN, CLEAR, and NEW. This processing │ │ has been added for all GW-Basic versions. │ │ │ │ 1.5) BSAVE and BLOAD │ │ IBM Basic appends the .BAS suffix to file names │ │ when the user does not supply a suffix. GW-Basic │ │ did not append a suffix. │ │ │ │ 1.6) CENTER OF GRAPHICS SCREEN │ │ IBM Basic calculates the center by dividing the │ │ one relative screen dimensions by two. GW-Basic │ │ calculates the center by dividing the zero │ │ relative screen dimensions by two. The IBM Basic │ │ method of calculating the center of the screen is │ │ now used by GW-Basic. │ │ │ │ 1.7) COMMON STATEMENT │ │ IBM Basic allows the user to define new variables │ │ using the COMMON statement. GW-Basic declared an │ │ error if a COMMON statement referred to a │ │ previously undefined variable. │ │ │ │ 1.8) LIST STATEMENT │ │ During PRINT and LIST processing, IBM Basic clears │ │ characters from the end of the print item to the │ │ end of line. All versions of BASIC now function in │ │ this manner. │ │ │ │ 1.9) CURSOR DESIGN │ │ A) The GW-Basic cursor is on only during character │ │ input requests from the keyboard. │ │ B) The IBM Basic displays different cursors for │ │ the Screen Editor overstrike mode and insert │ │ mode. │ │ The GW-Basic cursor is now turned off when │ │ printing characters to the screen. The cursor is │ │ turned to the user cursor when the PRINT │ │ statement terminates. When input is requested, │ │ the cursor is turned to the insert mode cursor │ │ or the overwrite mode cursor, depending on the │ │ Screen Editor mode. │ │ │ │ 1.10) INKEY$, INPUT$, INPUT │ │ A) INKEY$ did not return the same key codes as │ │ IBM Basic │ │ B) INPUT$ did not return the same key codes as │ │ IBM Basic. It should be noted that IBM Basic │ │ key codes returned to INKEY$ are not the same │ │ as IBM Basic keycodes returned to INPUT$ for │ │ all keys. │ │ C) Device input from "KYBD:" read no break (no │ │ interrupt takes place) if using the INPUT │ │ statement. An interrupt took place if │ │ INPUT$(N,kybd:) IS SPECIFIED. │ │ GW-Basic now provides the OEM with filters for │ │ mapping characters on input. These filters │ │ provide the capability of returning IBM Basic │ │ keycodes. │ │ │ │ 1.11) CHR$ │ │ Certain IBM character codes in the range │ │ [&H00,&H1f] have been assigned fonts and are │ │ printable. Other codes in this range have been │ │ assigned functions (such as carriage return). │ │ GW-Basic now provides filters which allow OEM to │ │ decide which codes in this range are printable │ │ and which specify control functions. │ │ │ │ 1.12) SCREEN function │ │ SCREEN function requests for the character at the │ │ current cursor position may return a zero in │ │ place of &H20 (space) for IBM if there are no │ │ non-space characters to the right of the │ │ specified cursor position. GW-Basic can now │ │ support this character code for the screen │ │ function. │ │ │ │ 1.13) POKE/PEEK │ │ Results of the POKE and PEEK statements were │ │ different. The GW-Basic machine interface now │ │ includes routines to filter PEEK and POKE │ │ instructions. The OEM may now modify the PEEK or │ │ POKE address and data value. Certain GW-Basic │ │ routines have been provided for use in these │ │ filters. GW-Basic provides the capability to │ │ support the function of all PEEK and POKE │ │ locations specified by IBM user documentation. │ │ │ │ 1.14) INITIALIZATION DIFFERENCES │ │ A) HEADING: GW-Basic displays the heading when a │ │ program is specified on the command line, │ │ while IBM Basic does not print a heading or │ │ display function keys in this case. The │ │ GW-Basic machine interface now contains a │ │ parameter that specifies to GW-Basic whether to │ │ print the heading and function keys when a │ │ program is specified on the command line. │ │ B) FUNCTION KEY DISPLAY: GW-Basic did not give the │ │ option of displaying the function keys when │ │ BASIC initializes, when there is no program on │ │ the command line. A configuration switch now │ │ specifies the function key display switch │ │ position on BASIC initialization. │ │ │ │ 1.15) ERROR CODES │ │ Some of the error codes and messages were │ │ different. GW-Basic error codes and messages have │ │ been modified to conform to IBM Basic. │ │ │ │ │ │ 1.16) MUSIC AND SOUND │ │ A) PLAY octave default not the same. │ │ B) BEEP duration not the same │ │ C) SOUND STATEMENT: │ │ 1)SOUND freq,0 causes the IBM Basic to be │ │ flushed │ │ 2)GW-Basic does not perform range checking on │ │ frequency. │ │ 3)SOUND statement foreground mode was not │ │ interruptable by CTL-C or BREAK. This is a │ │ problem because it is possible to create │ │ extremely long notes. │ │ These conditions are considered bugs and have │ │ been fixed for all versions. Foreground SOUND │ │ interruptability is available through a GW-Basic │ │ keyboard routine provided to the OEM for use │ │ within the speaker control support. │ │ │ │ 1.17) COLOR statement syntax │ │ The IBM COLOR statement syntax was not │ │ supportable by the GW-Basic OEM interface. This │ │ problem has been fixed in GW-Basic. │ │ │ ├────────────────────────────────────────────────────────────────────┤ │ │ │ 2) DIFFERENCES WHICH WILL NOT BE RESOLVED │ │ │ │ 2.1) SCREEN EDITOR DIFFERENCES │ │ (THESE DIFFERENCES MAY NOT EXIST IN SOME VERSIONS │ │ OF GW-BASIC BECAUSE OF THE FLEXIBILITY OF THE OEM │ │ INTERFACE FOR MAPPING AND OMITTING FEATURES) │ │ │ │ A) Input sequences that wrap to a subsequent │ │ physical line cause a scroll to open another │ │ physical line. IBM Basic allows the user to │ │ type over the text which is on the subsequent │ │ line. The IBM Basic end of logical line is then │ │ moved to the end of the logical line which is │ │ being overwritten. │ │ B) Skip-to-next-word function. When the cursor is │ │ positioned on a space the IBM skip-to-next-word │ │ control function will skip spaces until a word │ │ is found, progress over the word and proceed to │ │ the word following. The GW-Basic skip-to-next- │ │ word control function will skip spaces until a │ │ word is found. │ │ C) TAB. In GW-Basic, after stopping at the last │ │ position on a line, TAB will proceed to the │ │ next line. IBM Basic TAB only operates on one │ │ line. │ │ D) Cursor movement control functions do not join │ │ physical lines into logical lines. In IBM Basic │ │ cursor movement can join lines. │ │ E) Line delete. The GW-Basic Screen Editor uses a │ │ character other than ESC for line delete. │ │ F) GW-Basic extends logical lines to new physical │ │ lines (when required by LF or wrapping at the │ │ end of the screen). A new blank line is inserted │ │ following the current line. When physical lines │ │ following the first physical line in a logical │ │ line are deleted, the line is removed from the │ │ screen. In IBM Basic, lines are not inserted or │ │ removed. │ │ G) AUTO. The IBM AUTO statement allows the user to │ │ modify the statement corresponding to the line │ │ number printed by AUTO only. If the user uses │ │ the Screen Editor to move to another line, or │ │ otherwise attempts to modify the line number, │ │ strange results are obtained. The GW-Basic AUTO │ │ statement allows the user to modify any line by │ │ making use of the Screen Editor to modify the │ │ line number or to move to another line on the │ │ screen. │ │ H) Functions added to Screen Editor │ │ 1) HELP. This control function allows the │ │ programmer to edit the last statement where │ │ an error ocurred, or if no error ocurred, │ │ the last direct statement. │ │ 2) DELETE WORD. This control function deletes │ │ the current word starting at the current │ │ cursor position, and ending at the character │ │ previous to the next word │ │ 3) CLEAR TO END OF SCREEN. This control │ │ function clears all data from the current │ │ cursor position to the end of the screen. │ │ │ │ 2.2) Breaking from INPUT │ │ IBM Basic allows the user to break from an INPUT │ │ statement using either Control-C or BREAK. GW-Basic │ │ provides only one BREAK function code. This │ │ function code may be assigned to either BREAK, │ │ Control-C, or both by the OEM. However, no special │ │ processing is performed to differentiate between │ │ the INPUT statement and other statements. │ │ │ │ 2.3) Sequences returned by the GW-Basic RANDOM NUMBER │ │ GENERATOR (RND function) will NOT be identical to │ │ sequences returned by the IBM Basic random number │ │ generator. │ │ │ │ 2.4) /F and /S Options │ │ IBM Basic statically allocates file space using │ │ the /F and /S BASIC command line switches. GW-Basic │ │ allocates space dynamically and is not limited by │ │ these switches. GW-Basic will not declare an error │ │ if the user specifies either of these switches. │ │ │ │ 2.5) File Format of BASIC │ │ IBM Basic is in ".COM" file format. GW-Basic is in │ │ ".EXE" file format. │ │ │ │ 2.6) Fielded Strings │ │ IBM Basic fielded strings retain their values │ │ after the file is closed. In GW-Basic this space is │ │ deallocated. Any field statement which is executed │ │ while a file is opened, has no effect after that │ │ file is closed. For example, assume file 1 is │ │ opened, fielded, and closed. If file 1 is │ │ reopened, it should be refielded. │ │ │ │ 2.7) VARPTR │ │ In IBM Basic, the value returned by VARPTR for a │ │ given file number is not subject to change during │ │ program execution. In GW-Basic, FBD's are moved in │ │ memory when files are opened and closed. To avoid │ │ problems due to this difference, the statement │ │ "X=VARPTR(file)" should be executed before every │ │ referrence to X because a file buffer may be moved │ │ in memory when another file is closed. │ │ │ │ 2.8) Line Printer Filenames │ │ Line printer filenames have the following syntax: │ │ "LPTn:[bin]" │ │ Where if bin is included, the file is opened in │ │ Binary mode. In this mode, tabs are not expanded │ │ to spaces, and CR is not forced at end-of-line. │ │ │ │ 2.9) DATE$ │ │ Both IBM Basic and GW-Basic allow a single digit │ │ for year. IBM Basic interprets the digit 8 as │ │ 1980. GW-Basic interprets the digit 8 as 2008. │ │ │ │ 2.10) Pen and Joy Stick │ │ The statement 'STRIG ON' and 'STRIG OFF' perform │ │ no function in GW-Basic. In IBM Basic these │ │ functions are used to enable and disable the joy │ │ stick trigger interrupts. │ │ │ │ 2.11) Parity Checking on the OPEN statement │ │ There is an undocumented PE on the IBM OPEN │ │ statement. This OPEN option enables/disables │ │ parity checking on input. With no PE specified, │ │ the IBM OPEN for communications will report no │ │ parity errors. │ │ │ ├────────────────────────────────────────────────────────────────────┤ │ │ │ 3) IBM BASIC PROBLEMS FIXED IN GW-BASIC │ │ │ │ 3.1) Homing The Graphics and Text Cursor │ │ IBM Basic does not home the cursor after CLS in │ │ version A1.0. GW-Basic allows the OEM to choose │ │ when to home the graphics cursor. The text cursor │ │ is always returned home as per IBM PC Basic │ │ version A1.1. │ │ │ │ 3.2) NAME statement On Open Files │ │ IBM Basic allows the NAME statement to refer to an │ │ open file. This causes no immediate problem, but │ │ can lead to problems as in the following case: │ │ 10 OPEN"0",#1,"JUNK" │ │ 20 NAME"JUNK" AS "JUNK2" │ │ 30 KILL"JUNK2" │ │ 40 PRINT#1,"My data" │ │ 50 CLOSE │ │ IBM Basic allows this program to execute. Data │ │ printed to the file is lost. This is inconsistent │ │ in that KILL is illegal when referring to an open │ │ file. │ │ GW-Basic and the standard MS-DOS version of │ │ BASIC-86 do not allow NAME to refer to open files. │ │ │ │ 3.3) Detection Of Identical File Names │ │ IBM Basic does not detect identical file names │ │ when the only difference in the name is the case │ │ of the alphabetic characters comprising the file │ │ name. This problem prevents IBM Basic from │ │ detecting that a file in an OPEN statement has │ │ already been opened. │ │ GW-Basic and the standard MS-DOS version of │ │ BASIC-86 are able to detect this user error. │ │ │ │ 3.4) Interruptability Of Input From The Keyboard │ │ Variable length input (INPUT n,var...) from │ │ the keyboard is not interruptable using the break │ │ key. The program: │ │ 10 OPEN "KYBD:" FOR INPUT AS 1 │ │ 20 INPUT #1,A$ │ │ 30 GOTO 20 │ │ will read break as a character (the program is │ │ virtually uninterruptable). This problem is fixed │ │ in GW-Basic. │ │ │ │ 3.5) Communications │ │ 1) End Of File. IBM-PC Basic returns EOF true │ │ whenever the input buffer is empty. GW-Basic │ │ returns EOF true only when file was opened in │ │ non binary mode, and CTL-Z has been received. │ │ Once EOF is true, it remains true until the │ │ file is closed. This is more analogous to the │ │ way EOF works on other devices. │ │ 2) Default Data Bits. IBM Basic documentation │ │ states that the default bit count for │ │ communications is 7. The commas in the │ │ statement: │ │ OPEN "COM1:,,," │ │ cause 7 bit mode to be invoked. However, if │ │ parity or speed are specified, the default data │ │ bit count is set to 8. GW-Basic defaults to 7 │ │ data bits. │ │ │ │ 3.6) Graphics │ │ 1) POINT. The IBM BASIC POINT function does not │ │ detect that certain coordinates are not on the │ │ screen and therefore are not legal. │ │ 2) GET and PUT. The array format and speed │ │ capability of these statements is supportable │ │ by GW-Basic. However, the operation of these │ │ commands is highly dependent on hardware design │ │ and the implementation of OEM specific │ │ routines. │ │ │ │ 3.7) Screen Editor │ │ 1) The IBM Screen Editor returns a zero to input$ │ │ function when a null function key is depressed. │ │ GW-Basic Screen Editor returns no key code to │ │ INPUT$ for null function keys. │ │ 2) The IBM Screen Editor terminates function key │ │ expansion when a key code greater than &H7f is │ │ encountered. The high bit of this key code is │ │ removed. GW-Basic allows codes greater than │ │ &H7f. In late ROMs, the IBM Screen Editor will │ │ not remove the high order bit from codes │ │ returned by function key expansion. │ │ │ │ 3.8) Trailing Blanks │ │ The following BASIC program demonstrates a problem │ │ in IBM Basic: │ │ 10 OPEN "JUNK FOR OUTPUT AS #1 │ │ 20 PRINT #1,"ABC " │ │ 30 CLOSE #1 │ │ 40 OPEN "JUNK" FOR INPUT AS #1 │ │ 50 INPUT A$ │ │ 60 PRINT LEN(A$) │ │ 70 CLOSE #1 │ │ The IBM Basic result of the print statement in │ │ line 60 is 13. The trailing blanks have not been │ │ removed. GW-Basic removes these trailing blanks as │ │ specified by the ANSI Standard. │ │ │ ├────────────────────────────────────────────────────────────────────┤ │ │ │ 4) RS232 COMMUNICATIONS │ │ │ │ Previous releases of GW-Basic were incompatable with │ │ IBM-PC Basic communications in the following areas: │ │ 1) When a com file was opened with default │ │ parameters and closed, a CONTROL-Z (1A hex) was │ │ sent to let the other end of the RS-232 │ │ protocol know that end-of-file had been │ │ reached. This is not done in IBM-PC BASIC. │ │ 2) Under GW-Basic if a COM device was opened with │ │ the BIN option, EOF always returned false. In │ │ ASCII mode, EOF returned false until it │ │ received a CONTROL-Z, after which time it │ │ always returned true. │ │ These changes made EOF behave in a device independent │ │ manner. For example, a program which was written to │ │ read sequentially through a disk file, stopping when │ │ EOF was true, can now be used to read a COM file. For │ │ another example, GW-Basic can load "COM1:" and terminate │ │ when the load is finished if the user on the other end │ │ of the RS232 line types SAVE "COM1:",A. │ │ │ │ The number of application programs which have been │ │ written to use IBM-PC COM cannot be ignored. The │ │ following change in GW-Basic is intended to provide │ │ compatability with IBM-PC Basic while retaining the │ │ features added to GW-Basic. │ │ NOTE: This change is isolated to version independent │ │ code and has no effect on OEM written routines. │ │ │ │ COM files can be opened in one of the following ways: │ │ │ │ 1) With the ASC option │ │ In this mode, EOF is always false until a CTL-Z │ │ is received. When a file is opened for OUTPUT │ │ or RANDOM, a CTL-Z is sent when the file is │ │ closed. │ │ │ │ 2) With the BIN option │ │ In this "raw" mode, Basic performs no filtering │ │ of data. This includes forcing carriage return │ │ when line width is exceeded. This option │ │ overrides the LF option. EOF has the same │ │ meaning as it does in IBM-PC Basic. EOF is TRUE │ │ if no data exists in the input buffer. │ │ │ │ 3) With neither the BIN nor the ASC options. │ │ This mode is compatible with IBM-PC Basic. No │ │ CTL-Z is sent when the file is closed. EOF is │ │ TRUE if no data exists in the input buffer. │ │ │ │ BSAVE, BLOAD force the mode to BINARY. This insures │ │ BASIC will not force any Carriage Returns if the device │ │ is not 255 (infinite). │ │ │ │ SAVE "COMn:...",A forces the mode to ASCII. │ │ │ │ LOAD 'COMn:..." forces the mode to ASCII if the first │ │ character received is less than 80 hex, indicating an │ │ ASCII file is being loaded. This ensures that ASCII │ │ LOADs will terminate. │ │ │ │ COM file syntax: │ │ "COMn: [speed] [,parity] [,data] [,stop] [,RS] │ │ [,CS[n]] [DS[n]] [,CD[n]] [,LF] [,ASC] [,BIN]" │ │ Where: │ │ SPEED baud rate in bits per second │ │ PARITY N, E, 0 (none, even, odd) │ │ DATA 5,6,7,8 bits per byte │ │ STOP 1, 1.5, 2 stop bits │ │ Default for baud greater than 110 is 1 │ │ Default for 110 baud or lower & 5 data bits │ │ is 1.5 │ │ Default for 110 baud or lower & 6-8 data bits │ │ is 2 │ │ RS Suppress RTS (Request To Send) │ │ CS[n] Controls CTS (Clear To Send) │ │ DS[n] Controls DSR (Data Set Ready) │ │ CD[n] Controls CD (Carrier Detect) │ │ This is also referred to as RLSD │ │ (Receive line Signal Detect) │ │ LF Send a Line Feed character (X'OA') │ │ following a Carriage Return (X'OD') │ │ ASC Open COM file in ASCII mode │ │ BIN Open COM file in BINARY mode │ │ │ │ The RTS (Request To Send) line is turned on when you │ │ execute an OPEN "COM..." statement unless you include │ │ the RS option. │ │ If CD is omitted, it defaults to CSO │ │ If DS is omitted, it defaults to DS1000 │ │ If CS is omitted, it defaults to CS1000 │ │ If RS is specified and CS is omitted, then CS defaults │ │ to 0. │ │ │ │ Normally I/O statements to a communication file will │ │ fail if the CTS (Clear To Send) or DSR (Data Set Ready) │ │ lines are not cabled. The CS and DS options allow you │ │ to avoid this problem by ignoring these lines. If the │ │ [n] argument is included, it specifies the number of │ │ milliseconds to wait for the signal before returning a │ │ "Device Timeout" error. │ │ │ │ If the argument [n] in the CS, DS, and CD options is │ │ omitted, or equal to 0, then that line's status is not │ │ checked at all. │ │ │ │ NOTE: The speed, parity, data, and stop parameters are │ │ positional, but RS, CS< DS, and CD may appear in any │ │ order after STOP. │ │ │ │ When included in the parameter list, LF will cause a │ │ Line Feed to be sent after a Carriage Return. │ │ │ │ │ └────────────────────────────────────────────────────────────────────┘