ZBasic Language Reference
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ZBasic Microcontrollers
FixI(), FixUI(), FixL(), and FixUL() are specifically for converting Single values to the target
type. The difference between using FixI() and CInt(), for example, to convert a Single value is the
rounding method used. The final set of conversion functions, CType() and To<enum>() is for
converting an integral value to an enumeration member. See the ZBasic System Library Reference
Manual for more details on these conversion functions.
2.14 Parameter Passing Conventions
When a subroutine or function is defined, part of the definition specifies the parameters and their types
that are expected by the routine. These parameters are referred to as the “formal parameters”. When a
subroutine or function is invoked, parameters must be provided that match the formal parameters in
order, number and type. These parameters are referred to as the “actual parameters” for each
invocation.
As discussed earlier, parameters may be passed to subroutines and functions either “by value” or “by
reference”. The differences between these two methods are subtle but important. When passed by
value, the actual parameter may be an individual value like a constant or variable or it may be an
expression. In either case the value of the actual parameter is calculated and the resulting value is
passed to the routine. Within the called routine, the passed value may be utilized in any manner; it may
even be modified and this modification will have no effect on any of the constituent elements of the
passed parameter value. Effectively, the called routine gets its own private copy of the passed value.
When passed by reference, the address of the actual parameter is passed to the called routine. This
implies that the actual parameter must be an individual variable or another parameter and not an
expression nor a constant. Since the called routine has the address of the actual parameter, it is able to
both read from and write to the actual parameter unless otherwise restricted. The ability of a routine to
modify a variable passed by reference is often useful, especially in cases where a routine needs to
produce multiple values for use by the caller. On the other hand, if used carelessly, it can be the source
of errant program operation that is difficult to diagnose.
There are restrictions on whether a particular variable type may, may not, or must be passed by value or
by reference. For example, a persistent variable cannot be passed by reference because the called
routine is expecting the address of a RAM-based variable. Also, for efficiency reasons some variables
are always passed to routines by providing the variable address, even if the definition of the routine
specifies the parameter is to be passed by value. In such cases, the compiler treats the parameter as
being read-only, effectively enforcing the semantics of pass-by-value. Any attempt to modify a read-only
variable in the called routine or to pass it by reference to another routine will be detected and reported as
an error by the compiler. Arrays may only be passed by reference and then only if they are RAM-based,
single-dimension and have a lower bound of 1.
Allowed Parameter Passing Methods
Actual Parameter Type
Pass By Value
Pass By Reference
Constant or expression, any type
Yes
No
RAM-based variable or array element
Yes¹
Yes²
RAM-based single-dimension array, 1-based
No
Yes
RAM-based single-dimension array, not 1-based
No
No
RAM-based multi-dimensional array
No
No
Persistent variable or array element
Yes
No
Persistent Memory array
No
No
Program Memory array element
Yes
No
Program Memory array
No
No
Notes:
¹ String types and structures are read-only within the called routine when passed by value.
² The sub-byte types, Bit and Nibble, cannot be passed by reference. Also, in BasicX mode,
UnsignedInteger and UnsignedLong types are read-only within the called routine when
passed by reference.
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