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A block-oriented terminal is a type of computer terminal that communicates with its host in blocks usually consisting of chunks of text
With a block-oriented terminal, the terminal is sent a description of the fields on the screen by the host. The terminal then displays these fields and permits the user to edit them; when the editing operation is completed, the terminal submits the entire fields back to the host in one burst. Thus communication between terminal and host occurs in blocks of data. A web browser displaying an HTML form is an example of this: each block sent by a web server is called a "document" or "page", and the client's response is called "POST data".
Block-oriented terminals have the advantage of causing less system load on the host and less network traffic than character-oriented terminals. They are also more responsive to the user, especially over slow connections, since editing within a field is done locally on the terminal itself. This makes them especially ideal for data-entry applications.
The IBM 3270 and IBM 5250 are the main examples of block-oriented terminals. Although DEC systems mainly used character-oriented terminals, the VT131 and VT132 had a block mode capability.
The rise of web-based interfaces can be seen in some ways as a return to block-oriented terminals, due to their similarities; indeed, many applications today exist which will convert a block-oriented terminal stream (esp. IBM 3270) to an HTTP/HTML stream.
