Previous topic |
Next topic |
Contents |
Glossary |
Contact z/OS |
PDF
3270 data stream Networking on z/OS |
||
Prior to explaining the TN3270 implementation, you need to know a little more about the 3270 data stream. The 3270 data stream operations are designed primarily for transmitting data between an application program and a 3270 display with keyboard so end users can interact with mainframe-based applications. The 3270 data stream is also designed for transmission of data to 3270 printers. The 3270 data stream is implemented using a mapped character buffer in the device. In turn, this mapped character buffer forms the display on the screen. Data received from the application program and data to be transmitted to the application program are stored in a device buffer and displayed on the screen in the form of alphanumeric characters and symbols. The displayed data is updated when the end user modifies the buffer data and when new data is received from the application program. Each character storage location in the buffer maps to a character position on the display. All characters and numbers are represented through Extended Binary Coded Decimal Interchange Code (EBCDIC). Write control character (WCC) The 3270 write control character is often included in the 3270 data stream. It is used to sound a beep or to unlock the keyboard. Data stream commands The 3270 data stream commands
perform various functions. The basic 3270 data stream commands are:
While these commands appear straightforward, what is the meaning of, say, an unprotected field? All locations on a 3270 display screen are governed by field attributes. 3270 field attributes The field attribute defines
the start of a field and the characteristics of the field. Here are some common
field attributes:
Field attributes can be further modified using extended field attributes. Extended field attributes allow such characteristics as foreground and background colors and highlighting to be controlled. These 3270 data stream fields appear reasonably straightforward, but the implementation details can quickly become very complex; 3270 Data Stream Programmer's Reference provides exhaustive details. |
Copyright IBM Corporation 1990, 2010
|