3.1.3. Increment and decrement

We know how to perform common arithmetic operations. But there is also an operation that is common in programs, and does not have a specific mathematical symbol: incrementing the value of a variable in one unit:

   a = a + 1;

In C# there is a more compact notation for this operation, and also for the opposite operation (decrement):

   a++;           is the same as    a = a+1;

   a--;           is the same as    a = a-1;

But there is more to discover about increment (and decrement): we can distinguish between "pre-increment" and "post-increment." We can make assignments like this one:

   b = a++;

In this example, if "a" is 2, this instruction assigns to "b" the value of "a" and then increments that value of "a". Therefore, in the end we have b=2 and a=3 (post-increment: "a" is incremented after its value is assigned).

But if we write

   b = ++a;

which first increments "a" and then assigns it to "b" (pre-increment), so a=3 y b=3.

Of course, we can also distinguish post-decrement (a--) and pre-decrement (--a).

Suggested exercises:

Ø       Create a program that uses three variables x, y, z. Their initial values must be 15, -10, 2,147,483,647. It will increase the value of these variables. What results do you expect to get? Compare it with the results obtained by the program.

Ø       What would be the result of the following operations? a=5; b=++a; c=a++; b=b*5; a=a*2;

Also, in C# we can make multiple assignments:

   a = b = c = 1;