Page 78 - DCAP407_DATA_STRUCTURE

Unit 4: Pointers

Then, the elements of the matrix d are stored in memory row-wise as shown in figure 4.2:

Figure 4.2: Array of Pointers

By using array of pointers, you can declare d as:
int *d[3];
Here, d is an array of pointers, d[0] gives the address of Row 0, d[1] gives the address of Row 1, and
d[2] gives the address of Row 2. Now, d[0]+0 will give the address of the element in the 0 row and 0
th
th
column, d[0]+1 will give the address of the element in the 0 row and 1 column and so on.
th
st
In general, the address of the element in the i Row and j Column is given by:
th
th
d[i]+j
The element in the i Row and j Column can be accessed using “*” (indirection operator) by specifying
th
th
*(d[i]+j).
4.6 Records and Record Structures
Usually, collection of data is organized into hierarchy of fields, records, and files. A file is a collection of
similar records and a record is a collection of related data items, where each data item is called a field or
an attribute. Each data item can be a group item composed of sub items. The items which cannot be
decomposed are called elementary items, scalars or atoms. Identifiers are used to refer to the data types,
variables, and functions.
A record is a collection of data items that differs from a linear array in the following ways:
1. A record can be a collection of non-homogenous data (data items with different data types).
2. In a record, data items are indexed by attribute names. Therefore, there may not be a natural
ordering of the elements.
Under the relationship of a group item to sub item, “level” numbers can be used to describe the
hierarchical structure of the data items in a record, as shown in the following example:

Consider a kindergarten school maintaining a record of the admission application
it receives. The record contains the following data items: name, gender, date of
birth, father’s name, mother’s name, and address. Further, date of birth is a group
item with sub items month, day, and year, Father and Mother group items will
have sub items Name and Age, and Address group items will have sub items
Dno, Road, and Area.

The structure of the record can be as follows:
1 Application
2 Name //data item

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