pgbeg  : to start pgplot by specifying the display device (screen).
pgenv  : to define range and scale of the graph and to draw labels, axes etc.
pgpt   : draws a point.
pgline : draws a polyline(refer notes).
pgend  : closes the pgplot.
pgpage : clears the screen for the next page of display.
pgsvp  : define size of a viewport in normalized manner(0.0-1.0) : device independent..
pgvsiz : define size of a viewport in inches : absolute coordinates.
pgtext : to write a horizontal char string at a position in world coordinates.
pgptxt : write text at a position with given orientation and justification.
pgpoly : to draw a filled polygon.
pgrect : to draw a rectangle : doesnt work.
pgcirc : to draw a circle : doesnt work.
pgsci  : to set color.
pgscr  : to change color represented by a color-index.
pgsls  : to change line style.
pgslw  : to change line width.
pgsch  : to change character height.
pgscf  : to change character font.
pgstbg : to change text background.
pgsfs  : to change fill-area style.
pgqcol : gives min and max number of the color supported.
pgqch  : gives current char-height.
pgolin : interactively allows user to specify a set of points.
pgncur : similar to pgolin and points are sorted into increasing order of x.
pglcur : similar to pgolin and draws a continuous polyline through the points.

pgvstd : define a default standard viewport : device dependent.
pgswin : define a window using world coordinates.
pgbox  : to draw frame(box) around the viewport and to draw tickmarks.
pglab  : to label the graph and the axes.
pgbbuf : start buffering.
pgebuf : end buffering.