We talk about the various sources of Data - both static and dynamic - its features and differences.

1. 1.2 SOURCES OF DATA
H’MM

2. OBJECTIVES
The learners will be able to:
 Define Static Data and give examples
 Define Dynamic Data and give examples
 Compare the use of static information sources with dynamic information
sources
 Define direct and indirect data source
 Understand the advantages and disadvantages of gathering data from direct
and indirect data sources

3. DATA STRUCTURE
 What is a data structure?
“A data structure is a collection of data items that is
implemented by various development tools.”

4. STATIC DATA STRUCTURE
“MR. DEPENDABLE”

5. STATIC DATA STRUCTURE
 The size of the data structure is fixed
 Static data structures are very good for storing a well-defined number of
data items.
 For example, if we want to design an ID field for employees of an
organization. We can suggest it to be a fixed format e.g. “HIS000”; where
the 1st 3 characters are the initials of the organization and the other
three the employee number e.g. HIS225.

6. ADVANTAGES OF STATIC DATA STRUCTURES
 The development tool can allocate space during compilation
 Easy to program
 Easy to check for overflow
 Allows random access

7. DISADVANTAGES OF STATIC DATA STRUCTURES
 The developer has to estimate the maximum amount of space that is
going to be needed.
 A lot of space maybe wasted.

8. DYNAMIC DATA STRUCTURE
“MR. ADAPTABLE”

9. DYNAMIC DATA STRUCTURE
 There are many situations where the number of items to be stored in
NOT known in advance e.g. the length of someone’s name may NOT be
the same as any other’s name.
 In this case, the developer would be using a dynamic data structure. This
means that the data structure is allowed to grow and shrink as the
demand for storage arises.
 The developer should also set a maximum size to help avoid memory
collisions.

10. DYNAMIC DATA STATIC DATA
Memory is allocated to the data structure
dynamically.
Memory is allocated at compile time. Fixed size.
Limitation: As the memory allocation is dynamic, it
is possible to ‘overflow’ should it exceed it’s allowed
limit. It can also ‘underflow’ if it becomes empty.
Benefit: The memory allocation is fixed and so
there will be no problem with adding an removing
data items.
Benefit: Makes the most efficient use of memory as
the data structure – only uses as much memory it
needs.
Limitation: Can be very inefficient as the memory
for the data structure has been set aside regardless
we use it or not.
Limitation: Harder to program as the software
needs to keep track of its size and data item
locations at all times.
Benefit: Easier to program as there is no need to
check on data structure size at any point.