When you're getting bored of programming, you can always ask why:
>> why A very rich programmer wanted it that way.
By placing a semicolon at the end of a line, you suppress the output. For example,
>> diag([1 2 3 4])
ans =
1 0 0 0
0 2 0 0
0 0 3 0
0 0 0 4
>> diag([2 4 6 8]);
If you do not assign the last result to anything, it is automatically assigned to the variable ans:
>> x = 3 + eye(2)
x =
4 3
3 4
4 - 2*eye(2)
>> ans =
2 4
4 2
>> ans + x
ans =
6 7
7 6