abs = Returns the absolute value of a given value.
acos = Returns the arc cosine of a given value (inverse trig).
alog = Returns the natural logarithm of a given value.
alog10 = Returns the common logarithm (base 10) of a given value.
asin = Returns the arc sine of a given value (inverse trig).
assoc = Map a file into multiple arrays of specified type and dimension.
atan = Returns the arc tangent of a given value (inverse trig). 
axis = Draws an X,Y, or Z axis.  Good for multiple axes.
beseli = Returns the I Bessel function of order N for the given value.
beselj = Returns the J Bessel function of order N for the given value.
besely = Returns the Y Bessel function of order N for the given value.
bindgen = Return a byte array with each element set to its 1-d index.
breakpoint = Set or clear debugging breakpoints in routines.
bytarr = Create a byte array of 1 to 8 dimensions.
byte = Convert a number to type byte or a string to a byte array of ASCII codes.
byteorder = Change integer byte order. Convert floats between native and IEEE.
bytscl = Convert an array to byte, scaling from 0 to TOP (def=255).
call_external = Calls a function written in another computer language.
call_function = Call the IDL function given its name in a text string.
call_procedure = Call the IDL procedure given its name in a text string.
cd = Change or find the current working directory.
check_math = Can use to turn off some math error messages.
cindgen = Complex array with real part of each element set to its 1-d index.
close = Closes the specified files.
color_convert = Converts between RGB, HLS, and HSV color systems.
color_quan = Combines a true color image RGB components into 8 bit psuedo color.
complex = Combine real and imaginary values into complex.  Extract cmplx fields.
complexarr = Create a complex array of 1 to 8 dimensions.
conj = Gives the complex conjugate of a complex value (imaginary = -imaginary).
contour = Make a contour plot of a 2-d array.
convert_coord = Convert coordinates between device, normalized, and data.
convol = Convolve a 1-d or 2-d array with a given kernel.
cos = Returns the cosine of a given value (trig).
cosh = Returns the hyperbolic cosine of a given value.
cursor = Gives an interactive graphics cursor.
dblarr = Create a double precision array of 1 to 8 dimensions.
define_key = Program keyboard keys with string values or actions.
defsysv = Create a new system variable.
delete_symbol = (VMS only) Delete a DCL symbol.
dellog = (VMS only) Delete a VMS logical name.
delvar = Delete a variable at the main program level (and erase main program).
device = Control non-universal device dependent features.
dilate = Performs the morphological dilation operation on an image.
dindgen = Gives a double precision array with each element set to its 1-d index.
double = Converts a value to double precision.  Extract double precision fields.
empty = Writes out all buffered output for the current graphics device.
eof = Tests a specified file unit for end of file (EOF).
erase = Erase the graphics device to a specified background color (def=0).
erode = Performs the morphological erosion operation on an image.
errorf = Returns the error function of a given value.
execute = Execute at run-time IDL statements contained in a text string.
exit = Exit IDL and return to the operating system.
exp = Returns the natural exponential of a given value.
fft = Compute the forward or inverse Fast Fourier Transform of an array.
findfile = Return an array of filenames matching a given pattern.
findgen = Gives a floating array with each element set to its 1-d index.
finite = Tests if a float or double is finite or not a number (NaN).
fix = Convert a given value to an integer.  Extract integer fields.
float = Convert a given value to floatig point.  Extract floating point fields.
fltarr = Create a floating point array of 1 to 8 dimensions.
flush = Writes out all buffered output for the specified file units.
free_lun = Frees up specified file unit numbers, after closing files.
fstat = Gives a structure with file info (total bytes,loc,...) for a given unit.
gamma = Returns the gamma function for a given value.
gaussint = Returns the Gaussian integral for a given value.
get_kbrd = Checks if a keyboard key has been pressed or waits until one is.
get_lun = Allocates a file unit number (100-128) from a pool of free units.
get_symbol = (VMS only) Returns the value of a DCL symbol as a text string.
getenv = Returns the value of an environmental variable. (VMS log nam, symbol).
help = Gives main level help on the current IDL session: variables, routines,...
histogram = Gives the histogram (density function) of an array.
imaginary = Returns the imaginary part of a given complex value.
indgen = Gives an integer array with each element set to its 1-d index.
intarr = Create an integer array of 1 to 8 dimensions.
interpolate = Does linear, bilinear, or trilinear interpolation on an array.
invert = Computes the inverse of a matrix given as a square array.
ioctl = Gives access to the Unix ioctl(2) system call (see system C progr doc).
ishft = does right or left bit shifts on bytes, integers, or longs.
journal = Logs interactive IDL commands and results to a specified text file.
keyword_set = Tests if a keyword exists and is not 0. Good for true/false flags.
lindgen = Gives an long integer array with each element set to its 1-d index.
linkimage = Merges other language routines into IDL (call_external much easier).
lngamma = Returns the natural logarithm of the gamma fuction of a given value.
lonarr = Create a long integer array of 1 to 8 dimensions.
long = Convert a given value to an long integer.  Extract long integer fields.
lubksb = With ludcmp solves a set of linear equations.
ludcmp = With lubksb solves a set of linear equations.
make_array = General array creation routine. Good for most array creation needs.
map_continents = draws world continents after map_set initializes setup.
map_grid = Draws a latitude/longitude grid after map_set initializes setup.
map_image = returns an image warped to fit a map projection set up by map_set.
map_set = Initializes, and optionally draws, a selected map projection.
max = Returns the largest element of an array (and optionally the smallest).
median = Returns the median value of an array or does median smoothing.
message = Print an IDL like error or informational message.
min = Returns the smallest element of an array (and optionally the largest).
mprove = Iteratively improves the ludcmp solution to a set of linear equations.
n_elements = Number of elements in an array (scalars have 1) or 0 if undefined.
n_params = Number of non-keyword parameters given in a call to a routine.
n_tags = Number of tags in a structure.  Also size in bytes.
on_error = Set error handling action for errors in a user written routine.
on_ioerror = Set a statement label to jump to on an I/O error.
open = Open a specified file for input or output.
oplot = Overlays a plot of given data on a plot established previously by plot.
plot = Plots an x/y graph of given data.
plot_io = Plots an x/y graph of given data.  Linear X, Log Y.
plot_oi = Plots an x/y graph of given data.  Log X, Linear Y.
plot_oo = Plots an x/y graph of given data.  Log X, Log Y.
plots = Plots arrays or points in 2 or 3-d in device, normalized, or data coord.
point_lun = Sets or returns the current file byte position pointer.
poly_2d = Does polynomial warping of images. out(x,y)=in[a(x,y),b(x,y)].
polyfill = Fill inside of a 2-d or 3-d polygon visible on the display.
polyfillv = Returns the 1-d indices inside a polygon in a 2-d array.
polyshade = Returns a shaded surface image of a set of 3-d polygons.
print = Prints formatted output to the screen (standard output).
printf = Prints formatted output to an open file.
randomn = Returns one or more normally distributed numbers of mean 0 and SD 1.
randomu = Returns one or more uniformly distributed numbers from 0 to 1.
read = Reads formatted input from the keyboard (std input) into IDL variables.
readf = Reads formatted input from a file into IDL variables.
reads = Reads formatted input from a text string into IDL variables.
readu = Reads unformatted binary data from a file into IDL variables.
rebin = Resizes array dimensions to an integral multiple or factor of original.
reform = Reshapes an array. Ex: 2x6 -> 3x4.  Also drops leading dims of size 1.
replicate = Creates an array of 1 to 8 dimensions filled with a given value.
restore = Restores an IDL session or variables from a file made by SAVE.
rewind = (VMS only). Rweind a tape unit.
roberts = Does a Roberts edge enhancement on an image.
rotate = Efficiently rotate array multiples of 90 deg with optional transpose.
save = Save IDL session or variables to a file. May later restore and continue.
set_plot = Set the output device used by IDL graphics commands.
set_shading = Set up light source parameters for shade_surf and polyshade.
set_symbol = (VMS only) Defines a DCL symbol.
setenv = (Unix only) Sets or changes an environmental variable.
setlog = (VMS only) Defines a VMS logical name.
shade_surf = Returns a shaded surface image from a 2-d array.
shade_volume = Prepares a volume and threshold for 3-d shading by polyshade.
shift = Shifts array elements along any dimension by any number of elements.
sin = Returns the sine of a given value (trig).
sindgen = Gives an string array with each element set to its 1-d index.
sinh = Returns the hyperbolic sine of a given value.
size = Returns an array describing the size and type of the given value.
skipf = (VMS only) Skips files or records on magnetic tape.
smooth = Does boxcar averaging of an array of any number of dimensions.
sobel = Approximates the Sobel non-linear edge enhancement operator.
sort = Returns an array of subscripts to sort a given array in ascending order.
spawn = Executes operating system commands and optionally captures results.
sqrt = Returns the square root of a given value.
stop = Stops execution of a routine and returns to interactive mode. Debugging.
strarr = Creates a string array of 1 to 8 dimensions. Sets elements to null.
strcompress = Compresses or removes whitespace in a text string.
string = Convert a given value to a string.  May explicitly format result.
strlen = Return the length of a given string (converts arg to string if needed).
strlowcase = Converts a string to all lowercase letters.
strmessage = Returns an IDL error message given an error number.
strmid = Returns a substring of specified length and start from a given string.
strpos = Searches for a substring in a longer string and returns found position.
strput = Inserts a substring into another string by overwriting.
strtrim = Convert value to string & remove leading and/or trailing white space.
strupcase = Converts a string to all uppercase letters.
surface = Plots a wire mesh surface plot of a given 2-d array.
svbksb = Uses back substitution to solve a set of linear equations.
svd = Does singular value decomposition on a matrix.  Useful with svbksb.
systime = Returns date and time as a string or # seconds since 1 Jan 1970 (dbl).
tag_names = Gives a structure's tag names in a string array (and struct. name).
tan = Returns the tangent of a given value (trig).
tanh = Returns the hyperbolic tangent of a given value.
taprd = (VMS only) Reads the next record of a specified tape unit into an array.
tapwrt = (VMS only) Writes data from a array to a specified tape unit.
temporary = Conserves memory for array operations. A=temporary(A)+1 uses 1/2.
thin = Returns a skeleton of a bi-level image.  Medial axis of a shape.
total = Returns the sum of all array elements or sum over a specified dimension.
tqli = Gives eigenvalues & eigenvectors of a real,symmetric, tridiagonal matrix.
transpose = Returns the transpose of an array.
tred2 = Reduces a real, symmetric matrix to tridiagonal form (useful with tqli).
triangulate = Constructs a triangulation of a random set of planar points.
tridag = Solves tridiagonal systems of linear equations.
trigrid = Interpolate a regular array from known values at random points (2-d).
trnlog = (VMS only) Translates a VMS logical name.
tv = Displays a given image array on the display without autoscaling.
tvcrs = Position and/or turn on or off the display device cursor.
tvlct = Load a color table in RGB, HLS, or HSV color systems. Read back RGB.
tvrd = Read all or part of the image display area into an array.
tvscl = Displays a given image array on the display, autoscaling on min & max.
usersym = Set up a user defined plotting symbol (may be filled, up to 50 pts).
voigt = Computes a Voigt profile useful as a spectral line profile.
wait = Wait a specified number of seconds before execution continues.
wdelete = Delete a specified window.
weof = (VMS only) Write an end of file (EOF) mark on a tape.
where = Returns 1-d indices of non-zero elements of an array expression.
widget_base = Used to define a base widget as a container for other widgets.
widget_button = Used to define a button widget.
widget_control = Used to realize, manage, and destroy widget hierarchies.
widget_draw = Used to define a draw widget.
widget_event = Look for and return a widget event (should use xmanager instead).
widget_info = Obtains information about widgets and widget subsystems.
widget_label = Used to define a label widget.
widget_list = Used to define a list widget.
widget_slider = Used to define a slider widget.
widget_text = Used to define a text widget.
window = Creates a window (may give size & location). Use for multiple windows.
wmenu = Primitive graphical menu with mouse selectable items.
writeu = Writes unformatted binary data to a file from IDL variables.
wset = Use to select the currently active window.
wshow = Use to show or hide a selected window.
xyouts = Display text on the graphics device.
zroots = Find the roots of an m-degree complex polynomial by Laguerre's method.