Hi
where we r giving co code in transactions i mean in T codes
that is company code level, and with out co code 
transactions are client level.

Hi,
   client level is the heighest possition in the sap r/3 
architecture . from the following specifications are cleint 
level:1. business area 2. posting keys.3. document types 
4.in g/l master record COA level 5.genaral data of 
customer , vendor mr maintained at cleint level.
 2) co.code level: all globel settings for fiscal year 
varient, posting period varient, field status varient, Fi 
document number Ranges , cca, g/l mr another segment, 
customer, vendor mr for fi company code data segment

client: company code,fiscal year varient,posting period 
varient,chart of accounts,document types,number 
ranges,vendor/customer general data segments.

company code: payment terms,verify the xdo1

Hi reddy you have to write it aagain very clearly its bit 
confusing...Ravindra plz mention more for company code 
level. Thank you for posting.
Majid.