Contents of Implementation dependent characteristics

Implementation dependent characteristics

Trailing blanks of image are not transferred to the external file on outfile.outimage excepts it's a direct file.
A parameter to printfile.spacing with value zero gives the standard effect of overprint.
The procedures lock and unlock are not implemented.
All open external files are closed when a program is terminated.
The following directive lines is supported:
- % whitespace ...
  A directive line with a whitespace is treated as a comment line.
- %nocomment ...
  The rest of the line is treated as ordinary source text. Some other simula implementations will ignore this line, and give a warning message. But this can be useful as the following example shows. In this implementation formal procedures must be specified, but that should not be done in standard simula. This will work both on Lund (Simula implementation from Lund Software House AB, Sweden) and Cim:
```
PROCEDURE P(i1,P2);INTEGER i1;
%nocomment PROCEDURE P2 IS 
              INTEGER PROCEDURE P2
%nocomment      (i,j);INTEGER i,j;
           ;
```
- %comment
  Will cause the compiler to strip all lines until the corresponding %endcomment is reached. This directive may be nested.
- %eof
  Will cause the compiler to react as if the end of the source file was reached. Include files that is placed in a archive must be preceded with this directive line.
- %casesensitive ON/OFF
  The case sensitivity of identifiers and keywords is turned ON or OFF. Default value is OFF.
- %define name
  Define a name. Names such as aix, amigados, convex, cray hp9000s800, hppa, hpux, i286, i386, i486, mach, minix, msdos, mc68000, mc68010, mc68020, mc68030, mc68040, m88000, mips, next, ns32000, sony, sparc, sunos, ultrix, unicos, unix, vax and vms are defined dependent of the system. The name cim is defined for implementations that is generating C code.
- %error ...
  Will cause the compiler to believe that it has found an error in the source text. The message that is preceded on the line is printed as an error message.
- %ifdef name
  If name is not defined then the compiler will strip all lines until the corresponding %else or %endif is reached. If name is not defined then the compiler will strip all lines between the optional %else and %endif.
- %include filename
  Will cause the compiler to include the indicated file in place of the INCLUDE directive line. This directive may be nested, but only to a level of 10.
- %nameasvar ON/OFF
  If it is turned ON, then transmission mode for name is implemented as reference. This will produce more efficient code. Default value is OFF.
- %staticblock ON/OFF
  If it is turned on, then data objects will be allocated static instead of dynamic, and the compiler may generate more efficient code. This option should be used with care and should not be used for blocks which may have more than one active data object at a given time. The option may not be used for classes that are given as prefix or virtual procedures or procedures that are parameter to other procedures. It may not be used for external classes or procedures.
- %stripsideeffects ON/OFF
  If it is turned ON, then the compiler can generate more efficient code, but not necessary correct code due to evaluation order for expressions. Default value is OFF.
- %undefine name
  Undefine a name. If the name is not defined the directive line has no effect.
C is the only language supported for none-Simula external procedures. ``Kind'' is interpreted as ``C'', and the external-item is case sensitive. External C procedures must be specified in the following way:
External C procedure external-item is type procedure procedure-identifier parameter/mode/specification-part ; ;
The rules for external C procedures are:
- Avoid global symbols prefixed with ``__'', it may lead to conflicts with system names in Cim.
- The procedure may have any type, except ref. If the type is text, then the null terminated string returned from C is converted to a Simula text object.
- Parameters may not be a Simula-procedure, switch or label.
- Parameters transmitted by value are always copied. Text or arrays are allocated by malloc, and are not deallocated by Cim. It's the C-programs responsibility to dealloc the space.
- Parameters transmitted by reference or name are transmitted to C as pointer to. Array or text are transmitted to C by the location of the first element.
- External C procedures with variable number of parameters can be specified by use of ``...'' in the end of the parameter list. Printf and scanf can be specified as follows:
```
EXTERNAL C PROCEDURE printf IS 
   INTEGER PROCEDURE printf(t,...);TEXT t;;
EXTERNAL C PROCEDURE scanf IS
   INTEGER PROCEDURE scanf(t,...);NAME ...;TEXT t;;
```