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[MP 
EASI -- The User Interface 
There are many possible implementations of the IMP system. That chosen by 
PCI is to have a single, special task which handles all Input/Output between 
the user and the parameter file, making IMP application tasks independent of 
the user interface. This ensures a single, consistent interface for the 
whole system which may be written by several different applications 
programmers over an extended period of time. It also permits updates and 
enhancements of the user interface without affecting the application tasks, 
and vice versa. 
PCI's user interface task is called EASI. It is an interpretive programming 
language with a syntax similar to BASIC, so it is very easy for users to 
learn.  EASI allows interactive modification of the parameter file entries 
and invokes application tasks on request. PCI has taken a great deal of 
effort to ensure a uniform, helpful dialogue between the user and the 
computer system. However, EASI is more than just a user interface; it is a 
computer language (interpreter) which is modelled on BASIC. It is very easy 
for the user to use to develop automated systems, logging of operations, 
editing of procedures and automatic on-line HELP. The EASI/IMP System is a 
blend of interpreter/compiler languages where the user interface is a simple 
to use interpreter language, while the applications tasks are compiled 
programs used to quickly "crunch" through the requested tasks. 
EASI is only one of many possible interface designs. IMP permits many 
user-interface tasks to "live" side by side, each being used as the situation 
dictates. Other possible interfaces could include structured interpreter 
languages, highly specialized systems for a small subset of the applications 
or an interface tailored to Artificial Intelligence applications. 
The EASI user interface features include: 
structured on-line help for all applications 
* parameter assignment 
range checking of parameter values 
* vieving application program requirements 
* hierarchical directory search for applications 
* basic graphic capabilities 
* support for a variety of terminals 
isolation of the user from the operating system 
* easily constructed procedure creation, editing and deletion 
* nested procedures 
session history logging 
execution of any application program. 
All menus, messages, titles, warnings and prompts (i.e., everything that 
appears in the user interface except the on-line HELP documentation) are 
constructed from the control parameter dictionary and are not directly 
controlled by the application programs. This uncoupling of the user dialogue 
from the application tasks means that the entire user interface to an 
application package can be converted to another natural language in a few 
days without affecting the operation of the system. EASI may be used 
directly as the user interface in a mode equivalent to the BASIC direct (or 
immediate) mode. Typical direct commands let the user ask for HELP, examine 
parameters (with SEE command), set parameters (LET <Parameter>=<string of 
values>), examine the status of parameters currently set for a given task 
(STATUS <TASK>) and RUN tasks. The tasks may be compiled programs designed 
to operate with IMP or EASI Procedures. 
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