Computer Accessories User Manual

Table 1–2 (Cont.) Parameter Data Types

Data Type Description

longword 32-bit unsigned integer

ptr Longword pointer to data buffer

short Synonym for short int

short int 16-bit signed integer

unsigned long int 32-bit unsigned integer

void * Pointer to object of unknown type

1.3.2 Access

Access describes the way in which the called routine accesses the data speciﬁed

by the parameter. The access methods are described in Table 1–3.

Table 1–3 Called Routine Access Methods

Access Method Description

Read Data needed by the called routine to perform its operation is read

but not returned.

Write Data that the called routine returns to the calling routine is written

into a location accessible to the calling routine.

Modify Data is both read and returned by the called routine; input data

speciﬁed by the parameter is overwritten.

1.3.3 Mechanism

The parameter-passing mechanism is the way in which a parameter speciﬁes

the data to be used by the called routine. The passing mechanisms are

described in Table 1–4.

Service Format 1–3