The unrestricted access to global data, i.e let us say all functions use integer type as global data. If it is necessary to change the integer into long integer then the problem occurs. A change made in global data item may require re-writing all the functions that access that data item.
Real world modeling, In the physical world we deal with objects such as people, car etc. such objects are not like data and functions. Real world objects have both attributes and behavior, i.e eye color, job title, no. of doors in a car, tall , short etc are the examples of attributes. As it turns out attributes in the real world are equivalent to data in a program, Behaviour is something a real world object does in response to some stimulus, i.e laughing, moving, applying the banks etc. The behavior is represented by a function.
Lack of Encapsulation, Encapsulation is the mechanism to hide the complexity of the program or it will protect from the unauthorized access to the user.
This is the mechanism to protect the data from losing. But while the encapsulation concept is a powerful working tool, its lack of availability in structured programming means that programs will be longer.
The same or similar code will appear in more than one location. This also means that the programs will have a greater chance of errors.
The testing will be lengthy as well since every piece of code will have to be tested. Even if the code is without errors in one place, the same piece of code may appear in a different part of the program and could have problems there.
Because the code that is written may appear in different parts of the program, it can be vulnerable to different problems because of its location.
Programs have variables, which means that they can take on different values in different parts of the program. So the testing that is necessary to develop an error-free program can be time consuming.