Getting Started with TRANSACT (32247-90007)

6 Data Structures

So far, the examples have made little reference to Transact’s data structures. However, if

you go back and scan each example, you will ﬁnd that some form of the LIST verb exists in

each example. For many applications, what you see in the examples is all that is needed.

However, there are times when it is necessary to programmatically take more control over

Transact’s temporary data storage.

COBOL and Pascal have very well deﬁned data structures. This chapter will compare

Transact's data structures to those used by both of these languages.

Typically, high-level application development products have data structures that are not

well deﬁned. For many applications, this makes them very easy to work with to generate

reports and to update databases or ﬁles. By the same token, there are applications which

become, if not impossible, then extremely difﬁcult to implement with these products

because of their weak data structures.

Let’s start by using some lines from EX40 in Figure 5-12.

Figure 6-1. Transact Data Structures

1.1 define(item) lastkey i(4):

1.2 enter i(4),init=0;

1.21 define(item) valid i(4):

1.22 yes i(4),init=1:

1.23 no i(4),init=0;

1.24 list valid:

1.25 yes:

1.26 no;

1.3 list lastkey:

1.4 enter;

2 list(auto) vorderhead;

3 list(auto) vorderline;

3.1 level;