This is a simple circuit of programmable current source/regulator. This circuit is used to generate current. Here is the schematic diagram of programmable current source/regulator :
Programmable Current Source Regulator circuit schematic

This circuit uses L 200 as main component. The error amplifier of this circuit is disabled by shorting pin 4 to ground. The value R is used to fix the output Io :

Io=(V5-2)/R

The output voltage can reach a maximum value Vi
– Vdrop=Vi  2 V (Vdrop  depends on Io ).

[Source: SGS-Thomson Microelectronics Application Note]