What is the purpose of the Boeing SCAP module?
The Standardized Computerized Airplane Performance (SCAP) interface is a standardised model for calculating aircraft performance of air transport category aircraft. The SCAP standard is developed and maintained by IATA and leading aircraft manufacturers.

From the IATA website:


  One particularly complex requirement is the calculation of takeoff performance data. Most airlines use programs supplied by the airplane manufacturers for each airplane type, and interface these programs with their own computer operating environment, airfield database, and data output format requirements.
  
  In order to reduce the development effort for the airlines
  (interfacing with different airplane manufacturers' programs) and
  manufacturers (meeting individual airline requirements for
  customer-specific features) there are clear advantages in
  standardizing as much as possible the input/output features of these
  programs, and also data formats.
  
  Having recognised this potential benefit, IATA, ATA and several
  manufacturers set up a Standardized Computerized Airplane Performance
  Task Force (SCAP TF).


A  SCAP module is a FORTRAN program that implements the SCAP standard. It takes a set of well defined inputs to produce a well defined output. 

The advantage of this approach is that it is possible for a third party to design a software program that requires aircraft performance data without having access to this proprietary data. The software can then be used for aircraft performance calculations of any aircraft as long as it has access its SCAP modules. 

There are 6 SCAP specifications for Takeoff, Landing, Climbout, Inflight, Noise and APM (Aircraft Performance Monitoring). 

I don't have access to the official SCAP specification, but from what I can find online I gather that for take-off performance the following is required:


TODA (Take-Off Distance Available)
TORA (Take-Off Run Available)
ASDA (Accelerate Stop Distance Available) 
runway elevation
runway surface condition
runway heading
wind speed and direction
ambient Temperature
QNH
MEL/CDL items affecting performance
max take-off thrust and reduced (FLX) option
anti-icing options
flap settings
V1/VR (fixed or opt) 
V2/VS (fixed or opt)
minimum acceleration altitude
actual take-off weight


I gather the landing SCAP module needs:


LDA (Landing Distance Available)
runway surface condition
runway elevation 
runway heading
wind speed and direction
ambient temperature  
MEL/CDL items affecting performance
approach type (CAT I/II/III) 
anti-icing options
presence of residual ice
flap setting (fixed or opt)
expected landing weight