For people whose roots are embedded in the mainframe IBM world, 
client-server is  essentially distributed or remote presentation. This style 
maps a workstation Graphical User Interface (GUI)  front end onto an 
existing application's text-based screen. This   is also called Remote, 
Mapping, Front-ending or HLLAPI (High-Level Language Application 
Programming Interface). The  mode of operation is typically intelligent 
workstations intercepting and interrogating text-screen (e.g. 3270) data 
streams sent from a host for display in a windowed environment.This is   
"frontware" solution, where a GUI front end is added to an IBM/MVS 
3270/5250 application and is placed on a workstation.   However, most 
processing remains on the host or server, with the exception of user 
interface translation logic and possibly validation logic.  For example,  
data from an application program is sent to a 3270 screen program on the 
mainframe to be displayed. The  merged data is sent to the workstation as 
a 3270 data stream.The workstation interprets the data and converts it to 
graphical form in a window. (Typically every mainframe screen used by 
the application has a corresponding window on the workstation and vice 
versa). When the user enters the data in a GUI window, it is transformed 
by the frontware application into a corresponding 3270 data format and is 
sent to the host computer.