X12 is a messaging standard developed by the American National Standards Institute (ANSI) for inter-industry electronic exchange of business transactions i.e. electronic data interchange (EDI).
ASC X12, chartered by the American National Standards Institute, develops and maintains EDI standards to drive business processes globally.

How X12 is helpful in EDI
The ASC X12 body develops and maintains EDI standards to facilitate electronic interchange involving business transactions such as order placement and processing, shipping and receiving information, invoicing, payment and cash application data, and data to and from entities involved in finance, insurance, transportation, supply chains and state and federal governments. With over 320 + transaction standards available, ASC X12 standards help conduct every facet of B2B operations electronically.

X12 Structure

An X12 EDI document contains mandatory segments:

• Interchange Envelop (ISA/IEA)
• Functional Groups (GS/GE)
• Transaction Sets (ST/SE)

Interchange Envelop
This is the wrapping for all the data to be sent in one transmission. The Interchange Envelope includes a header (ISA) and trailer (IEA). The Interchange Control Header (designated ISA) appears at the beginning, whereas Interchange Control Trailer (designated IEA) appears at the end.
The Interchange envelop may contain one or more Functional Groups. Apart from this, envelop indicates the sender of the message, intended recipient, date and time of transmission and version of X12 in use.
The ISA contains delivery information for the package, for e.g.
Sender ID and Receiver ID are often called as EDI Alias.
Interchange Control Number (ICN) is incremented each time an ISA is generated for this sender and receiver relationship.
Functional Groups
Within an ISA there can be many Functional Groups, and within each Functional group there are many Transaction Sets of the same type. The Functional Group is defined by the header (GS) and trailer segments (GE).
The GS segment is similar to the ISA, but now identifies what kind of document this is:

The sender and receiver IDs are the same as in ISA.
 
Transaction Sets
Many Transaction Sets can be included in the Functional Group, but these must be of the same type. The Transaction set is defined by header (ST) and trailer (SE). The ST segment specifies the type of document same as GS, but it uses a three digit number to do so.
ST¦850¦60001
Here 850, specifies Purchase Order transaction.
The X12 standard defines the sequence of segments in the Transaction Set and the internal sequence of elements within each segment. The relation between segments and elements can be linked to the relationship between records and fields in a database environment.
A segment is composed of logically related pieces of information grouped into units. For example, one segment used in the Transaction Set might convey the complete address in form of city, state, postal code, and other geographical information. A Transaction Set may contain multiple segments such as an address segment might be used repeatedly to convey multiple sets of address information.
X12 is a messaging standard developed by the American National Standards Institute (ANSI) for inter-industry electronic exchange of business transactions i.e. electronic data interchange (EDI).
ASC X12, chartered by the American National Standards Institute, develops and maintains EDI standards to drive business processes globally.

How X12 is helpful in EDI
The ASC X12 body develops and maintains EDI standards to facilitate electronic interchange involving business transactions such as order placement and processing, shipping and receiving information, invoicing, payment and cash application data, and data to and from entities involved in finance, insurance, transportation, supply chains and state and federal governments. With over 320 + transaction standards available, ASC X12 standards help conduct every facet of B2B operations electronically.

X12 Structure

An X12 EDI document contains mandatory segments:

• Interchange Envelop (ISA/IEA)
• Functional Groups (GS/GE)
• Transaction Sets (ST/SE)

Interchange Envelop
This is the wrapping for all the data to be sent in one transmission. The Interchange Envelope includes a header (ISA) and trailer (IEA). The Interchange Control Header (designated ISA) appears at the beginning, whereas Interchange Control Trailer (designated IEA) appears at the end.
The Interchange envelop may contain one or more Functional Groups. Apart from this, envelop indicates the sender of the message, intended recipient, date and time of transmission and version of X12 in use.
The ISA contains delivery information for the package, for e.g.

Sender ID and Receiver ID are often called as EDI Alias.
Interchange Control Number (ICN) is incremented each time an ISA is generated for this sender and receiver relationship.
Functional Groups
Within an ISA there can be many Functional Groups, and within each Functional group there are many Transaction Sets of the same type. The Functional Group is defined by the header (GS) and trailer segments (GE).
The GS segment is similar to the ISA, but now identifies what kind of document this is:

The sender and receiver IDs are the same as in ISA.
Transaction Sets
Many Transaction Sets can be included in the Functional Group, but these must be of the same type. The Transaction set is defined by header (ST) and trailer (SE). The ST segment specifies the type of document same as GS, but it uses a three digit number to do so.
ST¦850¦60001
Here 850, specifies Purchase Order transaction.
The X12 standard defines the sequence of segments in the Transaction Set and the internal sequence of elements within each segment. The relation between segments and elements can be linked to the relationship between records and fields in a database environment.
A segment is composed of logically related pieces of information grouped into units. For example, one segment used in the Transaction Set might convey the complete address in form of city, state, postal code, and other geographical information. A Transaction Set may contain multiple segments such as an address segment might be used repeatedly to convey multiple sets of address information.[:]