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S B M F O R T R A N A FORTRAN answer to 'C' The best road is designed by the traveller. Copyright (c) 1989-1991 by DUKE DAIGH Pine Bluffs, Wyoming 82082-0631 DISCLAIMER This is the initial release of SBM FORTRAN. It is probable that there are bugs. It may NEVER be totally bug-free. For this reason we make the following statement. This program is supplied as-is. The author disclaims all warranties, expressed or implied. The author assumes no liability for damages which might result from the use of this program. You are encouraged to freely distribute this package. Mail copies to friends. Put it up on other boards. We only request that you distribute only unmodified copies. Direct all inquiries, suggestions, etc. to: Duke Daigh P.O. Box 631 Pine Bluffs, Wyoming 82082-0631 CONTENTS Introduction to SBM fortran. . . . . . . . . . . . . . . . . . . . iii Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iv Current status . . . . . . . . . . . . . . . . . . . . . . . . . . v Fortran statements . . . . . . . . . . . . . . . . . . . . . . . . 1-1 Statement lables . . . . . . . . . . . . . . . . . . . . . . . . . 1-1 Symbolic names and keywords . . . . . . . . . . . . . . . . . . . 1-1 Statement order . . . . . . . . . . . . . . . . . . . . . . . . . 1-1 Comments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2 Include . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2 Data types . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3 Byte, Character, Integer*1, Logical . . . . . . . . . . . 1-3 Word, Integer, Integer*2 . . . . . . . . . . . . . . . . 1-3 Doubleword, Integer*4 . . . . . . . . . . . . . . . . . . 1-3 Character strings, ASCIIZ . . . . . . . . . . . . . . . . 1-3 Quoted strings . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4 Data declaration and initialization . . . . . . . . . . . . . . . 1-5 Data statement . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5 OPEN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1 UNIT (5-255). . . . . . . . . . . . . . . . . . . . . . . 2-1 IOCB names . . . . . . . . . . . . . . . . . . . . . . . 2-1 FILE . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1 ALIAS (alternate name for io unit). . . . . . . . . . . . 2-1 STATUS (old, new, append) . . . . . . . . . . . . . . . . 2-1 RECL . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1 READ STATEMENTS . . . . . . . . . . . . . . . . . . . . . . . . . 2-2 Unformatted . . . . . . . . . . . . . . . . . . . . . . . . 2-3 formatted . . . . . . . . . . . . . . . . . . . . . . . . . 2-4 List directed . . . . . . . . . . . . . . . . . . . . . . . 2-4 Next character from keyboard (NEXCHAR). . . . . . . . . . . 2-4 WRITE STATEMENTS . . . . . . . . . . . . . . . . . . . . . . . . . 2-5 Unformatted . . . . . . . . . . . . . . . . . . . . . . . . 2-5 formatted . . . . . . . . . . . . . . . . . . . . . . . . . 2-5 List directed . . . . . . . . . . . . . . . . . . . . . . . 2-6 SHOW_CHAR (display a character on screen) . . . . . . . . . 2-6 CRLF (write cr,lf to specified IOCB) . . . . . . . . . . . 2-6 FORMAT STATEMENTS . . . . . . . . . . . . . . . . . . . . . . . . 2-7 Field and edit descriptors. . . . . . . . . . . . . . . . . 2-7 ARITHMETIC EXPRESSIONS . . . . . . . . . . . . . . . . . . . . . . 3-1 INC, DEC (incrementing and decrementing variables. . . . . 3-1 ADD, SUB (adding to, or subtracting from variables . . . . 3-1 Subscripts . . . . . . . . . . . . . . . . . . . . . . . . 3-2 CONTROL STATEMENTS TEST, TEST Numeric. . . . . . . . . . . . . . . . . . . . . 4-1 Control flags . . . . . . . . . . . . . . . . . . . . . . . 4-1 Conditional transfers . . . . . . . . . . . . . . . . . . . 4-1 Compare variable to constant, CMP . . . . . . . . . . . . . 4-2 Compare string to string . . . . . . . . . . . . . . . . . 4-2 Unconditional transfers, GOTO, JMP . . . . . . . . . . . . 4-2 WAIT . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2 PAUSE . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2 STOP, CALL EXIT . . . . . . . . . . . . . . . . . . . . . . 4-2 TABLE_LOOKUP . . . . . . . . . . . . . . . . . . . . . . . 4-3 IF statements . . . . . . . . . . . . . . . . . . . . . . . 4-4 Block IF . . . . . . . . . . . . . . . . . . . . . . . . . 4-5 Do-loops . . . . . . . . . . . . . . . . . . . . . . . . . 4-8 RESERVED WORDS AND ARRAYS. . . . . . . . . . . . . . . . . . . . . 5-1 The command line (command tail) . . . . . . . . . . . . . . 5-1 Useful program constants . . . . . . . . . . . . . . . . . 5-1 Miscellaneous Intrinsics . . . . . . . . . . . . . . . . . . . . . 6-1 COPY Array_1 to Array_2 . . . . . . . . . . . . . . . . . . 6-1 FIND_CHAR 'c', Array . . . . . . . . . . . . . . . . . . . 6-1 END Ignored by the compiler. . . . . . . . . . . . . . . . 6-1 Masking operations. AND, XOR, OR . . . . . . . . . . . . . 6-1 SHIFT Shift a variable. . . . . . . . . . . . . . . . . . . 6-1 PARSE String, Keword . . . . . . . . . . . . . . . . . . . 6-1 PARSE_ONLY String, Keword, 'char' . . . . . . . . . . . . . 6-1 LDA. Load address . . . . . . . . . . . . . . . . . . . . 6-2 UPCASE. Convert string to upper case . . . . . . . . . . . 6-2 SYSTEMS STUFF . . . . . . . . . . . . . . . . . . . . . . . . . . 6-3 EXCLUDE_RTL . . . . . . . . . . . . . . . . . . . . . . . . 6-3 LABEL variable, word/byte. . . . . . . . . . . . . . . . . 6-3 PRESET data-type,variable . . . . . . . . . . . . . . . . . 6-3 SETFORM 'c' . . . . . . . . . . . . . . . . . . . . . . . . 6-3 SETIF 'c' . . . . . . . . . . . . . . . . . . . . . . . . . 6-3 Ramdisk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-1 Known bugs . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-1 INTRODUCTION TO SBM FORTRAN This manual describes SBM FORTRAN. SBM is based on American National Standards Institute FORTRAN 77 language. It is assumed that the reader has knowledge of an existing FORTRAN language and is familiar with MSDOS or PCDOS operating system. This manual is not intended to teach FORTRAN, but is intended to be used as reference material only. The original intention of SBM fortran was the author's answer to the 'C' language. The cryptic nature of 'C', while appealing to many programmers, leaves me cold. While I fully appreciate the power of the 'C' language (as with assembler), I felt that there was needed something that would better suit my style. I also remember when I brought my first XT home. There were many fortran-written utilities that I had on the Z-80 without which I felt very helpless. By the time I had rounded up the money to buy the system, I had none left for the software that I very sorely needed. An affordable compiler of an easily learned language seemed to the the answer. A good reason for someone, such as I, to write SBM fortran. The powerful fortran systems that are now on the market are designed with the high-level user in mind. Program size is not important. I needed something that would generate about the same code as if I wrote the it in assembler. This compiler operates by converting FORTRAN source code into assembler instructions, which are then converted into machine code using WASM, an assembler written by ERIC TAUK, of Merengo, IL. The result is a COM file, which can then be run on any MSDOS based system. THIS IS VERSION 1.00. To most of us this means a system that works well enough for the author, but sometimes awkward for the user. Here is a problem. I am in the process of moving to Wyoming. Here in Denver, I have access to many excellent bulletin boards. In Wyoming, that will not be the case. I must therefore release this version knowing that there may be bugs. Since I will no longer have easy access to the boards, I will not longer have easy access to you, the user. I must therefore go to a 'shareware' mode. To provide this connection, You must send me your name and mailing address. That will make you a registered user. To receive ANY updates of this compiler, you MUST be a registered user. At a minimum, I will upgrade to provide some of the functions that I need. Registered users will receive the first (or most recent) update. I most certainly need your suggestions for improvements and bug removal. If you like this compiler as I believe you will, your $20 contribution will be appreciated. Since I will no longer have access to the boards, that's the only way that you can receive the update. MSDOS is a registered trademark of Microsoft Corporation. PCDOS is a registered trademark of IBM Corporation. iii FEATURES OF SBM FORTRAN It is a compiler compiler. It was conceived as a bootstrap system to compile parts of itself. That's why I refer to it as my answer to 'C'. You can insert assembler coding and macros. You can invoke the standard interrupts. In other words, you can do anything with this compiler that you can do in assembler. In fact, some of the more complex modules of the compiler are WRITTEN IN FORTRAN. Any future refinements will be written in fortran. The executable module is very compact and efficient compared to other, higher-level compilers. It combines the simplicity of fortran coding with the power of the assembler. You can operate it as you would any other F77 compiler and end up with code that will usually run on any other F77 compiler. You can place more than one statement on each record. You can append comments to each statement. The compiled module uses buffered input, making it very fast. Pathnames are used so that you can access data on other drives and in other directories. All console/keyboard i/o can be re-directed. It has many powerful intrinsic operations, such as: PARSE, COPY, TABLE-LOOKUP, COMPARE, etc.. You can do masking operations, such as AND, OR, XOR. You can shift variables left or right, by the number of bits that you specify. iv CURRENT STATUS OF SBM FORTRAN BE VERY CAUTIOUS USING ANY SORTWARE! Do not trust it! Even if you have been using it for awhile, mentally EDIT the output. Does it look reasonable? You are the best judge. SBM fortran is not a scientific compiler. i.e., it does not have floating point. Integer*4 is there, but needs more hooks before it can be used. Arithmetic expressions are primitive, but gramatically correct and transportable. This feature will be upgraded to some extent. Needs more diagnostic messages. SBM fortran is not just forgiving. It's actually permissive. But, on the other hand, if you accept the above limitations, and write a program using standard fortran coding techniques, it will work, and the code can be put up and run under most other F77 compilers, without modification. FUTURE OF SBM FORTRAN SBM fortran was not, and is not intended to be a full-blown fortran compiler. It is not intended to compete with the more powerful systems. Integer*4 is one feature that will certainly be implememted. With large integers, you can do quite a lot. Accounting work and other related types of work require precise calculations. Large integers makes that precision possible. Instead of dollars and cents, you can carry everything in total cents. i.e. $156.25 is 15625 cents. For output, the format statement can direct that a decimal point be inserted (this feature is already installed, but not yet usable). The compiler needs compile time and runtime error detection that it does not now have. Some errors simply lock up the system. That is something that must be addressed in the first update. The direction of its future is mostly up to you. I have some floating- point routines that could be implemented, but I will probably not work in that direction unless there's enough response. The routines are in another fortran compiler of mine which I chose not to release at this time. There's another feature, TONTO (trace-on, trace_off), that might also be moved from my other compiler. v 1-1 FORTRAN STATEMENTS There are two types of statements, executable and non-executable. Non-executable statements are used to describe the characteristics and format of data. Executable statements specify actions that the program is to take against, or for the welfare of the data, such as READ, WRITE, etc.. Each source input line can be as long as 80 characters. Statement Continuations are permitted only on certain statements. they are: OPEN, FORMAT, data initialization. You can use statement labels to identify and reference individual statements in a program. You can label any statement but only labled statements can be referenced. SYMBOLIC NAMES AND KEYWORDS Symbolic names, chosen by the programmer, identify program variables and statement lables. A keyword is a pre-assigned identifier that you use to specify a particular action that the program is to take. Keywords are also known as RESERVED WORDs (see 5-1). A symbolic name is a sequence of one to 31 alphanumeric characters. When used to identify program variables, the first character must not be numeric. The name may consist of just about any printable character except for + - * / ( ) ; | apostrophy or comma. You cannot use reserved words to identify program variables. Standard fortran labels consist of numeric lables only. SBM fortran allows either, except for lables of format statements, which must begin with a numeric digit 0-9. Lables cannot begin with + - * ; |. Lables cannot use ( ) [ ] apostrophy or comma. Reserved words may be used as lables. Statement lables must begin in column 1. All other statements must begin in any column other than 1. By all means use column 7 if you wish to adhere to an accepted standard. You can assign more than one lable to a statement if you wish. In doing so, you can refer to it by either label. More than one statement may appear on each source input record by terminating each (except the last) with the marker code '|'. (on most keyboards this is uppercase backslash) The format of the additional statements is no different than the first, so don't forget to follow the marker with at least one blank, unless it is to be a label. STATEMENT ORDER Doesn't matter. mix or match. the compiler will sort them out. 1-2 COMMENTS - You can use a semi-colon(;), an asterisk(*) or hyphen (-) in column 1 to specify that the line is a comment. In addition, if you place a ';' anywhere in the statement portion of a source line, the rest of that statement will be treated as a comment. A blank line is also considered to be a comment. Individual assembler code statements can be inserted anywhere by placing a plus (+) in column 1. INCLUDE Blocks of fortran statements, assembler code, and macros may be inserted using the INCLUDE option. Syntax: INCLUDE pathname Pathname can name any file that is currently on line, on any disk. To include assembler code or macros, the statement must have a '+' in column 1 and the pathname must be in quotes. Example: + include 'maclib.asm' A small macro library is provided to generate some of the code that the compiler needs. You may build one of your own choosing and insert it using the + INCLUDE option. 1-3 DATA TYPES * SBM provides three data types: BYTE, WORD and Doublewords. BYTE data occupies 8 bits (one byte) of memory and is normally only used for ascii characters and strings, or logical variables, such as programmer-specified switches and flags. You can use this data type for numerical values, up to 255. WORD data are numbers that are whole positive, negative or zero-value numbers. WORD data values occupy 16 bits (two bytes) of memory and can contain numbers from -32,768 to 32,767. Although a word can hold a number as large as 65,635, this implementation provides no standard way to output the larger numbers. * DOUBLEWORDs are 32-bit (integer*4) integers. The may contain numbers within the range -2,147,483,648 to +2,147,483,647. Integer*4 data is very useful for accounting applications where larger numbers are involved and precision is required in transactions. For example, monitary amounts can be set into integer*4 variables using total cents, rather than dollars and cents. When the results are to be printed, a special feature of integer*4 values allows you to insert decimal points where applicable. In SBM FORTRAN, the following mean the same: CHARACTER, BYTE, INTEGER*1, LOGICAL 8-bit data. INTEGER, WORD, INTEGER*2 16-bit data. CHARACTER strings appear in memory as a collection of ASCII characters terminated by a binary zero. This zero terminator controls all operations in which this data type is manipulated, such as compares, copys, input-output, etc.. With the terminator, this is known as as an ASCIIZ string. * Integer*4 is not totally implemented. Some parts of it are. Some not. I wouldn't recommend that you try it yet. It will be implemented in the next update. 1-4 QUOTED STRINGS Over the years, we programmers have created a standard that would not be acceptable to people other than programmers. That is, calling an apostrophy a quote! When we think of quoted strings, we think of an ascii string enclosed in apostrophies, not quotes. Don't know how this started, but we all do it. Anyway, format statements sometimes require us to specify a 'quoted' string for output. With this in mind, in this manual, when we talk of a quoted string, we mean a string that is enclosed in apostrophies. When entering a quoted string that we wish wish to contain an imbedded quote, SBM FORTRAN requires that you use an ACTUAL quote("). Standard fortran wants you to use two apostrophies in a row. We do it differently here. example: standard fortran requires: FORMAT('We sometimes don''t follow standards') We do it this way: FORMAT('We sometimes don"t follow standards') 1-5 DATA DECLARATION and INITIALIZATION There are two modes in which you can declare variables, (1) declare and (2) declare/initialize. (1) Declare. The 'standard' declaration in which you specify the size of individual elements and optionally set aside a specific amount of memory to contain these elements in an array. Example: INTEGER ELEV(20), DIST(20), SLOPE, DELTA(3) (2) Declare/initialize. This mode allows you to declare a variable or an array and establish it's initial value(s). When initializing arrays, only as much memory as needed to contain the given data will be allocated. This statement can be continued. When used, this option must be the last (or only) declaration on the source statement. You can, of course, put multiple statements on one physical record. Examples: integer day/5/| integer month/12/| integer year/1948/ integer*1 level(4), mace/3/ character pathname/'c:sales.jan',0/ This statement is tricky. If you forget the closing '/', the compiler will search the rest of your source looking for one. Here's another example, taken right out of the compiler itself: character registers/ 'AX',0,'BX',0,'CX',0,'DX',0,'SI',0,'DI',0,'BP',0 'AL',0,'BL',0,'CL',0,'DL',0,'AH',0,'BH',0,'CH',0 'DH',0,'[SI]',0,'[DI]',0,'[BX]',0,'[BP]',0,'$'/ If you want to declare an array of a certain size but initialize only the first portion, here's another example from the compiler: character outbuf(80) data outbuf/'e:sbm.t$$',0/ THE DATA STATEMENT This is an executable statement! Most fortran reference manuals don't admit it but it is. Because of this fact, it can be used anywhere in the program. As you see above, you can initialize a variable or an array with it. You can also change data values on the fly. Over and over. Here's a handy use of this feature: If(code.eq.4) DATA table/1,2,3,4,5/ If(code.eq.5) DATA table/6,7,8,9,0/ 2-1 OPEN statement The OPEN statement establishes the connection between a fortran UNIT and a file or device. You must issue this statement before any diskfile I/O can be used. Note: you cannot close a file and re-open. syntax: OPEN(UNIT,ALIAS=buff-name,FILE='filespec',status='old/new/append', RECL=nnn) where: UNIT is a numeric constant, in the range of 5-255. The unit number is converted to a control block name by appending the number to 'IOCB_'. The unformatted input record can be referenced by this name (as well as any alias that you may specify). Unit 10, for example may be referenced by the name 'IOCB_10'. An example of this can be found under UNFORMATTED READ. ALIAS is an alternate name by which the file can be addressed when reading unformatted (raw) data. Raw mode, when used instead of formatted or list-directed input results in much faster i\o. Unformatted i/o is discussed more fully in READ statements. This parameter is optional. FILE='filespec'. Pathnames can be used here. You may name a file that is to be used, or specify a character array which contains an ASCIIZ filespec. If the name itself is used here, it must be enclosed in quotes. If an array containing the filespec is used, it must not be quoted. STATUS='old/new/append'. If the file is to be created, use 'new'. If the file is to be read/write, use 'old'. If you have an existing file that is to be enlarged, use 'append'. If you use 'new', any existing file by that name will be replaced. If you omit this parameter, 'old' is assumed. The quotes are optional, for compatability. RECL=nnn. SBM uses a buffered input system, resulting in very high-speed input. The buffering system uses two arrays. one for the input buffer, (into which is loaded blocks of non-predictable pieces) and the record buffer which will contain only the individual record. It is from the record area that formatting takes place. You can use the RECL option to insure that no record exceeds a given size. If this option is omitted, record length defaults to 80. 2-2 READ STATEMENTS READ statements transfer data from a specified I/O unit to memory. You can reference both external and internal files. The input data may be any ASCII stream. Syntax: READ(UNIT [,FMAT]) list UNIT is one of: (1) An integer constant in the range of 5 to 255 that identifies an external unit previously referenced in an OPEN statement. (2) An asterisk (*) specifying the default I/O unit (console). May be redirected. (3) The name of an internal array (such as the input buffer) containing data. This is the manner by which you can re-read a data record. explanation: on any read, the data is read into the input buffer as raw data. If a format has been specified, the record is transformed into the corresponding input fields. But: even after formatting, the raw data is still in the input buffer. FMAT is a parameter that specifies whether explicit or list-directed formatting is to be applied. It may take either of the following forms. (1) A statement label of a format statement. The statement label must begin with a numeric character 0-9. The rest of the label can be anything of your own choosing. (2) '*' that specifies list-directed formatting. If FMAT is omitted, a 'null' read is performed, effectively passing over an input record. The unformatted contents of the record are not lost, however, but are preserved in the input-output control buffer (IOCB). The string is available by its IOCB name, and may be treated as any other character array. LIST names the variables, arrays, array elements and character strings to which data will be transferred. If end of file is sensed, the logical variable 'EOF' is set to TRUE. 2-3 UNFORMATTED READ Syntax: READ(UNIT) list This is the most simple of the input statements. It transfers one record of binary data to the array 'list'. No conversion takes place. (A typical file of data information is stored as ASCII characters. No conversion is required if all you want to do is to examine it. It is considered to be binary data) If 'list' is omitted, one record is by-passed. For that reason it is sometimes referred to as a 'null' read, or 'by-pass' read. The contents of the record are available in the IOCB or under the ALIAS that was specified in the 'open'. Here's an example of how you might use it to read and display a file. open(5,file='reform.for') 1000 read(5) if(eof) stop write(*) iocb_5 goto 1000 end Type this one in and try it. It will make your hair stand on end! If you were to try this example on a large file, you can see that it wouldn't do you much good. The output would fly by so fast that you couldn't read most of it. 2-4 FORMATTED READ Syntax: READ(UNIT,FMAT]) list This is a two-step operation. Step 1 reads the record into the IOCB (an unformatted read). Step 2 applies the formatting and transforms the ascii data into the various input fields. LIST-DIRECTED READ Syntax: READ(UNIT,*) list Read statements are either unformatted or formatted. The difference in a list-directed read is that the compiler is going to create a format for itself, based on what kind of data we have in the 'list'. This is a two-step operation. Step 1 reads the record into the IOCB (an unformatted read). Step two applies the compiler-designed formatting and transforms the ascii data into the various input fields. NEXCHAR Reads a character from the keyboard. Does not echo to the console. If no character is ready, waits for operator to enter one. The character is available to the program in register AL. Execution resumes. See 'testall.for' for a practical example. (NEXCHAR and WAIT are same) 2-5 WRITE STATEMENTS WRITE statements transfer data from memory to a specified I/O unit. You can reference both external and internal files. Syntax: WRITE(UNIT [,FMAT]) list UNFORMATTED WRITE Syntax: WRITE(UNIT) list This statement transfers one record of ascii data to UNIT. The data must be terminated by a binary zero. No formatting takes place. If 'list' is present, it must be the name of an array. If omitted, the formatted contents of the IOCB is written. This is the form of output that you should use to insert control characters, such as escape-sequences, extra line feeds, backspaces, etc. Example, from 'testall.for' data outbuf/esc,'[2J',0/ write(*) outbuf ; clear the screen FORMATTED WRITE Syntax: WRITE(UNIT,FMAT]) list This is a two-step operation and is the revese of formatted read. Step 1 formats the specified data fields from binary to decimal as required and copies ascii data or quoted strings into the IOCB. Step 2 writes the contents of the IOCB to the specified UNIT. 2-6 LIST-DIRECTED WRITE Syntax: WRITE(UNIT,*) list In a list-directed write, a format is constructed by the compiler based upon the data type of the various fields. Other than that, it is exactly like the formatted write. While most compilers require that the first character of an output record be used for carriage control, SBM fortran does not. When output is to be directed to a printer, feel free to insert ascii control codes, 0Ch for eject, 0Dh for double space. SHOW_CHAR Display the character that is in the AL register. You can use this statement immediately after NEXCHAR. SHOW_CHAR 'char' Display specific character. The character can be a printable character enclosed in quotes, or a hex constant. Example: show_char 8 gives us a back-space on the console. 2-7 FORMAT STATEMENTS Format is a labled non-executable statement that specifies the format of data being transferred between memory and i/o devices. It may appear anywhere in the program. The first character of the label must be numeric. The method by which formatting takes place is by the use of field and edit descriptors with which the type and size of the various data fields is specified and quoted strings for constant ascii data. Each field descriptor consists of letter which identifies the type of data, followed by a number indicating the width of the data field. In some cases the width is optional. Format control proceeds from left to right, matching each field descriptor with each item in the i/o list. SBM uses 3 field descriptors, A, I, X Character data. The 'A' field descriptor transfers character data. It has the form A[w] If W is present the field width is w-characters. If omitted, the field width is the size of the data item in the i/o list. The name in the list can be any data type, character, logical or integer. On input, any existing data is simply overlayed. Integer data I[w] If the output binary number, when converted to decimal, exceeds the allocated space, the number will back-flow into the previous field, replacing whatever the formatter just put there. (not like standard fortran, which would fill the output field with asterisks. If enough of you complain, I will comply with the standard). Skip [w]x Quoted strings. Dollar sign descriptor $ Normally, all output records are terminated by a carriage return. The dollar sign descriptor inhibits this action. The option is intended for interactive I/O and is valid only for output statements. It permits user response to appear on the same line as a prompt. example: WRITE(*,*) 'Enter project number: ',$ READ(*,*) PROJ When used, the dollar sign descriptor must the the last item of the output statement. 3-1 ARITHMETIC EXPRESSIONS SBM fortran does not yet support more than a simple one-function expression. The simpler form of an expression, while requiring more statements to complete some calculations, still maintains compatability with higher-level compilers. Thus, we are limited to such statements as: counter=counter+1 range=limit-base etc.. String expressions allow a little more versatility, such as: filespec='c:modemuf.asm' letter='A' etc.. In addition to the above arithmetic statements, SBM fortran also supports the following statements: INC, DEC Add or subtract 1 from an integer variable. This is the most efficient way to add or subtract the constant 1 from a variable. example: inc counter ; add one to 'counter' dec tally ; subtract one from 'tally' ADD, SUB Add or subtract constant or value from register from an integer variable. This is much faster than standard fortran and uses less code. example: add index,10 ; add 10 to index. index=index+10 ; the usual, less ; efficient way. 3-2 SUBSCRIPTING Any variable may be accessed by using the variable name in a fortran statement. To access variables in positions other than the first, you must (1) use an integer offset or (2) use a subscript. An integer offset may be used by simply appending the variable name with a plus-or-minus constant. Example: 'ARRAY+4' points to the fifth position of a integer*1 or character array. If the array was integer*2, it would point to the third position, since each element in an integer*2 array requires two positions. While this is not a standard fortran method of accessing data, it is by far the most efficient. Subscripts, on the other hand, indicate the position of an element by enclosing a subscript expression within a pair of parentheses. The subscript expression can be an integer constant, and integer variable, or an integer variable plus-or-minus an integer constant. Examples: array(k), date(m+2), etc.. Other informative examples can be found in the program 'TESTALL.FOR'. A word of caution: Do not allow the expression to go negative. You will access something, but who knows what... 4-1 CONTROL STATEMEMTS There's no point in writing a program if you can't control what it does. Without flow control, a program would sequentially execute each of your statements and then blow up. That would be tacky. Fortran flow control statements provide a means of modifying the normal sequemntial flow of execution. Flow control statements are: TEST, COMPARE, CMP, DO, CONTINUE, GOTO, JMP, STOP and CALL EXIT. Some of these are not standard but all are handy. TEST Usage: TEST VARIABLE, MASK or TEST VARIABLE, NUMERIC You can test a variable using a mask, or TEST NUMERIC. When a TEST is performed, control flags are set, depending upon the results of the test. You must then use an if-statement or conditional jump. Control flags are: equal, not equal, zero, not zero, carry and not carry. (EQ), (NE), (ZR), (NZ), (CY), (NC), (NUMERIC), (NOT.NUMERIC) CONDITIONAL JUMPs are JNC, JC, JZ, JNZ Using a MASK, you can see if a particular bit or any one of a group if bits is set. It does this with a logical AND, and sets flags but changes nothing in memory. Example: see if an integer is odd or even. test(answer,1) if(zr) goto even (or) jz even To test an individual ascii character to determine whether it is numeric or not, use the following syntax: TEST VARIABLE, NUMERIC This checks an ascii character to see if it is within the range of '0' - '9'. As a result of this test, the logical variable 'numeric' is set to either true or false. Example: test(inbuf(1),numeric) if(not.numeric) goto alpha 4-2 CONTROL STATEMEMTS CMP variable, constant Compare a variable to a known value. This statement is identical to it's ASM equivalent. Subscripts are not permitted, but offsets can be used. Usage: CMP Name, 'A' CMP Name+2,'B' CMP Year, 99 This statement essentially subtracts the constant from the variable, does not change any values in memory but, sets the control flags. You must then use a conditional jump for program control. COMPARE Compare a string of characters against a model. Not case sensitive, 'TOKEN' should be upper case. Usage: COMPARE KEWORD, 'TOKEN' Example, from the compiler. - see if prefix 'byte' or 'word' compare keword,'BYTE' ; if(eq) goto destin_ok ; if 'byte' or 'word', compare keword,'WORD' ; accept it as-is. if(eq) goto destin_ok ; GOTO Unconditional transfer of control. JMP Same as GOTO WAIT Wait for operator. Program execution stops. When operator has pressed any key, execution resumes. PAUSE ['message'] Stops, waits for operator. If message included, displays the message. Otherwise, displays the phrase 'FORTRAN PAUSE'. Execution of the program will continue with the press of any key. STOP, CALL EXIT Use either to close all files, update directory and return control to the operating system. 4-3 TABLE_LOOKUP Given a character string, tests to see if the string exists in a specified table. Each entry in the table must be enclosed within quotes and must be in upper case. each entry must be followed by binary zero. The table must be terminated by a '$'. If the given string is found to be present in the table, register CX indicates it's relative position in the array. i.e., in the table below, AX=1, BX=2, CX=3, etc. If the string cannot be found, CX=0 and carry-flag is set. Here's a sample table. character registers/ 'AX',0,'BX',0,'CX',0,'DX',0,'SI',0,'DI',0,'BP',0 'AL',0,'BL',0,'CL',0,'DL',0,'AH',0,'BH',0,'CH',0 'DH',0,'[SI]',0,'[DI]',0,'[BX]',0,'[BP]',0,'$'/ The following example wants to see if the character string that is in the array 'keword' is any of the entries in the table 'registers'. - see if a destination is register. table_lookup keword,registers if(nc) goto destin_ok TABLE_ADD Following a table-lookup operation, adds a string to a given table. While this is not a control statement, it is included here because it is frequently used immediately following a non-successful table_lookup. Example: install the string in the array 'keword' in the table. - new symbol, put it in table. table_add keword 4-4 IF statements An IF statement conditionally executes one statement or a block of statements. The IF statement has the form: IF (exp) stmt Where exp is a logical or relational expression. In a LOGICAL IF statement, we have, as the result of a TEST or input/output operation, a condition of true(non-zero) or false(zero). The statement, or block of statements, will be executed only if the condition is true. In a logical IF, exp simply names the logical variable. In addition to the normal variable names, SBM fortran also allows the following: (EQ), (NE), (ZR), (NZ), (CY), (NC) or (EOF), (NOT.EOF), (NUMERIC), (NOT.NUMERIC) stmt can be any non-labled executable statement, but not another IF. The RELATIONAL IF statement performs an on-the-fly comparison of a variable to a known value. Character-strings can be compared, no matter what their length, but only for EQ or NE. Other operators may be used, but use with caution. The comparison is NOT case sensitive. The relational IF has the following syntax: IF (VARIABLE.OP.Constant) stmt where OP will be EQ, NE, LT, GT, LE, GE Constant may be (1) numeric, (2) Ascii character (excluding ';' and '|') , or (3) AsciiZ string. 4-5 There are two types of IF statements: o The single IF o The block IF (The arithmetic IF is not supported by SBM fortran) The single IF statement conditionally executes a single statement. It has the form IF (exp) stmt where: exp is a logical expression. stmt is a single, not continued, fortran statement. 4-6 The block IF conditionally executes blocks of statements. It has the following form: IF (exp) THEN block ELSE block ENDIF where: exp is a logical expression. THEN must appear on the same line. block is a series of statements, none of which can be another block-IF. The ENDIF terminates the block-IF construct. 4-7 There are two types of data which can be compared in an IF statement, numeric or literal. Literals are recognized by the presence of quotes. Here are some examples: * Author used the following program to test out and debug IF statements. integer ibuf write(*,*) 'enter a number: ',$ read(*,*) ibuf if(ibuf.eq.100) then write(*,*) '---------------' write(*,*) 'number is equal' else write(*,*) 'number is NOT equal' endif if(ibuf.lt.100) write(*,*) 'number is LT 100' if(ibuf.le.100) write(*,*) 'number is also LE 100' if(ibuf.gt.100) write(*,*) 'number is GT 100' if(ibuf.ge.100) write(*,*) 'number is also GE 100' stop - - - - - - - - - - - - - - - - - - - - - - - - ; this program reformats a WASM LST file to straight ASM format. You ; might want to do this to have a source that has the macros expanded. open(5,file=infile,status='old',recl=132,alias=inbuf) loupe read(inbuf) if(eof) stop if(inbuf.eq.20h) goto loupe if(inbuf.eq.'L') goto loupe if(inbuf+22.eq.20h) goto loupe write(1) inbuf+26 jmp loupe 4-8 DO Statement Here you can specify that a block of statements be executed for a specific number of times. Syntax: DO label index=first,last where: label is a numeric statement label of a CONTINUE statement which is forward from this statement. index is an integer*2 variable that will be set, and then incremented. first is an integer constant. last is an integer constant. CONTINUE statement Used only in conjunction with the DO statement, this statement is labled and is used as the terminator of the block of statements to be executed. Example: from "testall.for" do 809 counter=1,10 write(16,309) counter 309 format('test output record',i3) 809 continue 5-1 RESERVED KEYWORDS and ARRAYS FORTRAN has many keywords that are meaningful to the compiler, such as IF, READ, WRITE, etc.. In addition to the standard list of reserved keywords, SBM fortran includes some options not provided in other systems: LDA, EXCLUDE, WAIT, JMP, JNC, JC, JZ, JNZ, AND, XOR, OR, SHIFT, SETFORM, SETIF, SHOW_CHAR, INCLUDE, UPCASE, INC, DEC, TEST, ADD, SUB, CMP, LABEL, PARSE, COPY, NEXCHAR, TABLE_LOOKUP, TABLE_ADD, COMPARE, FIND_CHAR, CRLF, PRESET. YOU CANNOT USE RESERVED WORDS AS VARIABLE NAMES, although any of them may be used as statement lables. In addition to the above reserved words, we also have the following arrays, which are considered as reserved words: COMMAND, CONSOLE, INFILE, WORKBUF, OUTFILE, WORKBUF2. THE COMMAND LINE One of the problems facing the high-level programmer is how to access the data that we entered at the system prompt. SBM fortran sets this data where it can be easily used. The command tail can be located in the character array COMMAND. From there it can be parsed or otherwise used just like any other character array. In addition, the first two tokens are parse into INFILE (alias WORKBUF) and OUTFILE (alias WORKBUF2) and may be used as filenames in the OPEN statement. The advanced programmer will find these options to be of significant value. PROGRAM CONSTANTS Rather than using numerical equivalents for commonly needed constants, you may choose from the following list of pre-assigned symbolic names. CR Carriage return. Use instead of 0Dh, 13 decimal. LF Line feed. Use instead of 0Ah, 10 decimal. ESC Escape. For ansi screen control, 1Bh, 27 decimal. FF Form feed. To eject the page in printer files. TAB BS Back space. COMMA Equivalent to 2Ch. QUOTE Equivalent to 27h. QUOTES Equivalent to 22h. False Equivalent to binary zero. True Equivalent to binary 1. 6-1 MISCELLANEOUS INTRINSIC FUNCTIONS COPY Array_1, Array_2 Copies a character string to another array. Can be indexed. FIND_CHAR 'c', Array Searches a character string until the specified character is located. END Optional for compatability. Ignored by the compiler. AND, XOR, OR Masking operations Usage: AND variable,mask. Mask is hex constant, register, memory. SHIFT Shift a variable, left or right. Usage: SHIFT VARIABLE [,nbits] Shifts the variable the number of bits specified. If nbits absent, shift the variable one bit right. Otherwise you must specify the number of shifts. If nbits is preceded by a minus sign, shift is to the left. Example: shift 'number' one bit right. SHIFT NUMBER nother: shift 'number' 3 bits left. SHIFT NUMBER,-3 If you wish to shift only one bit left, it can be more efficiently done by adding the number to itself. It accomplishes the same result. Example: ibuf=ibuf+ibuf or better yet: ax=ibuf add ibuf,ax 6-2 MISCELLANEOUS INTRINSIC FUNCTIONS PARSE STRING, KEY [, 'delims'] Given the ascii STRING, isolate the first token. Copy the isolated token to KEY and shift STRING left to remove the token KEY. Delimiters are blank, comma or equals. Carry is set if no data available to parse (EOR). You can specify an additional list of delimiters to be used. Example: Consider the string 'now is the-time' parse string,keword,'(/-+' After the parse, keword will be 'now' string will be 'is the-time' carry is not set. PARSE_ONLY String, Keword, 'char' Parse until a specific character is found. We ignore the standard delimiters. In fact, the standard delimiters (including blanks) are passed to the 'keword' array. Example: As above, the string 'now is the-time' parse_only string, keword,'-' After the parse, keword will be 'now is the' string will be 'time' LDA Load address to a register: LDA VARIABLE, REG UPCASE Convert a character string to upper case. Usage: UPCASE String 6-3 SYSTEMS STUFF Things on this page are of no value to users. They are included here only for Author's convenience. LABEL variable, word/byte. Allows alias in system modules. Must be issued immediately before the data decalaration statement. PRESET data-type,variable Establish name and type in symbol table for external variable. data type is byte/word. SETFORM 'c' Change default character in format name. Normally fmt_nnn. Changes the 't'. Sample: fma_001. SETIF 'c' Change default character in if-labels. Normally true_000. Changes first '0'. Sample: true_a01. Example of the above two. SETFORM a| SETIF a 7-1 Greater speed can be realized by using a ramdisk. To take advantage of this feature, include in your autoexec.bat file the following: SET RAMDISK=d Where 'd' is your ramdisk drive. i.e. SET RAMDISK=E In the batch files, notice the commands SET BATCH=TRUE and SET BATCH=. These two commands are used by the compiler to determine the course or action when the requested source file cannot be found. They are of no concern for normal operations and should not be disturbed. 8-1 KNOWN BUGS I am aware of the following bugs. If I take time to correct them now, I may not get this system on the boards before I move to Wyoming. They will be addressed in the next update. 1. If you re-define a variable, you get no error message but all sorts of seemingly unrelated problems. 2. if(inbuf.eq.';') SBM.ASM(get_record) Input takes the ';' as begin comment, thereby truncating the statement.