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Obviously, “+'' was chosen to implement the add operation. We could read the part ``i + j'' as “add the value of j to the value of i'', thus at the ADT level this results in
{ Precondition: Let i = n 1 and j = n 2 with n 1, n 2 particular Integers }
i.add(j)
{ Postcondition: i = n 1 and j = n 2 }
Implementation of ADT:
Step 3: add
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 postcondition ensures that i and j do not change their values. Please recall the specification of add. It says that a new Integer is created the value of which is the sum. Consequently, we must provide a mechanism to access this new instance.