Functional Specs - Please Help

Question

I am very new to SAP FICO. I want to know how do you write a func. spec.  I have searched in this forum but I didn't get enough example. Please help me to know how write a func. spec. in detail. A real time example and how to write is what I am looking for.
Something about functional specs for  reports, user-exits, routines, interfaces and external table definitions with example is higly appreciated.
If you want to email me my email is arun4sap[at]gmail[dot]com.
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Answer 1

Hello,
I copy pasted a functional spec below.
ITs basically telling the Abapper what exactly has to be done.
The Abapper should know what has to be done by looking at the funcitonal spec alone( usuall they have a million questions after)
Points will be appreciated
Regards,
Zaid
Functional Specification –
DEV ID          Sales tax report
Functional Team          Zaid Azam     
               (phone)
SAP Dev.  Team     (lead)      Zaid Azam      (phone #)
     (member)      (phone #)
Phase / Priority     Phase 1
     Medium
Revisions
Rev. Id     Rev. date     Author     Description
00               Initial release
1     Report definition
Basic Information
Report type 1     A/P
Report type 2     Printed
Language requirem.     
Printer requirement     Local printer / system printer
Paper requirement     Landscape
Source environment:     R/3
Module:     FI
Suggested technique     ALV / other
Triggered:     Manually
Frequency:     On-demand
Volume:     Daily
2     Functional Requirements
Functional Requirements
Selection     Posting Date,  G/l account
Narrative flow     The report should list the all the transactions of the G/l account( all items i.e open and cleared) selected on the initial screen. It should list  the vendor name and number when a G/l transaction is of a vendor
Assumptions / issues     
Should have the capability of being exported to excell
3     Processing logic
Processing logic
Step 1     Enter g/l account (HKONT) on the selection screen and run with or without a date range Or run by a  date range only without specifying a G/L
Step 2     Get the G/L number from BSIS that was selected on the initial screen Or get all the G/ls that had postings in the posting date  ( BUDAT) specified on the initial screen.
Step 3     Get the amount ( WRBTR) from BSIS ( Open and cleared both are in BSIS)
Step 4     Take the Document Number (BELNR) from BSIS and get the vendor number for that doc number  from BSIK ( open item), from BSAK ( cleared) if item is paid.
Step 8     Should get the vendor name from LFA1 for the vendor number from BSIK or BSAK
Step 9     
Step 10     
4     Output
4.1     Layout
FORMAT                                        
G/L     Posting date   Amount         Doc type      Text                         Doc number          Pk     Vendor #     Name
650100     12/03/2006     500     SA     Test for report     19000042342     40     10229      GMC
4.2     Header elements
SAP Field     Report Field                          Comment
BSAK LIFNR,BSIKLIFNR     Vendor number     
LFA1_NAME1        Vendor Name     
BSIS_BUDAT     Posting Date     
BSIS_HKONT     G/l account     
4.3     Line item
SAP Field     Report Field                          Comment
BSIS_WRBTR      amount     
BSIS_BLART               Document type     
BSIS_SGTXT     Item text     
BSIS_BSCHL             Posting Key     
5     Additional topics
Additional topics
Unit Test Suggestions:     Same as the standard SAP report FBL3N. Only addition is the vendor name and number
Security/ Authorizations:     .
Error handling     
Dependencies     
References     
Out of scope requirements     NA