
Define
X and Y to be two different integers

Print
their sum and difference to the terminal screen

Repeat,
all on one IDL command line, using the "&" character

Repeat
all of the above, using the recall buffer ("up" arrow)

Print
the result of adding 3 times X to 2 times Y

Print
the product of (XY) and (X+Y)

Print
the common logarithm of the absolute value of X+Y (use the ABS and ALOG10
functions)

Confirm
this result by raising 10.0 to the power you just obtained

What
is the difference between X = 5/2 and Y = 5./2 ?

Between
X = FLOAT(5/2) and Y = FLOAT(5)/2 ?

Set
C equal to the numerical value of the speed of light in cgs units

Successively
print powers of C until you locate the point at which the result becomes
"Inf".

What
power yields this result? [The answer is noninteger.]

Now
define C to be the speed of light in double precision.

Repeat
the exercise above [Hint: you should accelerate all such exercises by making
liberal use of the recall buffer and line editing.]

String
example: define a string variable for each word in the sentence:
"This is a concatenation"; then concatenate them and print the
result.