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The first line defines three instances i, j and k of type Integer. For each instance the special operation constructor should be called (Allocation memory). In this example, this is internally done by the compiler. The compiler reserves memory to hold the value of an integer and ``binds'' the corresponding name to it. If you refer to i you actually refer to this memory area which was ``constructed'' by the definition of i. Optionally, compilers might choose to initialise the memory, for example, they might set it to 0.
Implementation of ADT:
Step 1: Instances definition
MODULAR PROGRAMMING
int i, j, k; /* Define three integers */
i = 1; /* Assign 1 to integer i */
j = 2; /* Assign 2 to integer j */
k = i + j; /* Assign the sum of i and j to k */
Consider the ADT Integer. Outline the relationship to the ADT Integer in the following code:

| The last section introduces abstract data types (ADTs) as an abstract view to define properties of a set of entities. Object-oriented programming languages must allow to implement these types. Consequently, once an ADT is implemented we have a particular representation of it available.
| Consider again the ADT Integer. Programming languages such as Pascal, C, Modula-2 and others already offer an implementation for it. Sometimes it is called int or integer. Once you've created a variable of this type you can use its provided operations. For example, you can add two integers: