Double Byte Character

Key Characteristics

• • Storage: Each DBC occupies exactly two bytes of storage, regardless of the specific character, contrasting with SBCs which use one byte.
  • Encoding: Often used within an extended EBCDIC environment (e.g., EBCDIC DBCS) or in Unicode (UTF-16, where many characters are 2 bytes, or UTF-8 where they can be multi-byte sequences).
  • Mixed Data: DBCs can coexist with Single Byte Characters (SBCs) within the same data string, requiring specific shift-out (X'0E') and shift-in (X'0F') control characters in EBCDIC DBCS to delimit DBC sequences.
  • System Support: z/OS provides extensive support for DBCs across its components, including COBOL, CICS, DB2, IMS, and utilities, through specific data types and processing routines.
  • Display and Printing: Requires DBCS-capable terminals, printers, and software to correctly render the characters, often involving specific font libraries and display drivers.

Use Cases

• • International Applications: Developing applications for global markets that require storing and processing names, addresses, and other textual data in languages like Japanese, Simplified Chinese, Traditional Chinese, or Korean.
  • Database Storage: Storing customer information, product descriptions, or legal documents in DB2 or IMS databases using GRAPHIC or VARGRAPHIC data types to accommodate non-Latin scripts.
  • User Interfaces: Displaying screens and reports in CICS or batch applications that present information to users in their native double-byte languages, often leveraging BMS maps with DBCS fields.
  • Data Exchange: Interfacing with external systems that use multi-byte character sets, requiring proper conversion and handling of DBC data during file transfers, API calls, or message queuing.

Related Concepts