This chapter provides an overview of the VT220 terminal. The chapter describes the VT220's major features and operating modes.
The VT220 (Figure 1-1) is a general-purpose, video display terminal that uses ANSI standard functions. The terminal has two major components, a monitor/system unit and keyboard.
The following sections summarize the major VT220 features.
The VT220 uses a monochrome monitor with the following features.
24 rows × 80/132 columns
7 × 10 dot matrix in a 10 × 10 cell for 80 columns
7 × 10 dot matrix in a 9 × 10 cell for 132 columns
800 (horizontal) × 240 (vertical) pixels (80 columns)
1188 (horizontal) × 240 (vertical) pixels (132 columns)
This list summarizes the major VT220 text features.
The VT220 provides the following major communication features.
The VT220 has three operating states.
Set-Up
The set-up state lets you select or examine terminal operating
features (such as transmit and receive speeds) from the keyboard.
You can also use set-up to select the on-line and local states. The
VT220 Owner's Manual describes set-up in detail.
You select set-up by pressing the Set-Up key.
On-Line
The on-line state lets the terminal communicate with a host
computer. Data entered at the keyboard is sent to the host
computer. Data received from the host computer is displayed on the
monitor. You can also display data entered from the keyboard, if
you select the local echo feature in set-up or with a control
sequence.
You can only select on-line from set-up.
Local
The local state lets you place the host computer on "hold". Data
entered at the keyboard is sent to the monitor, but not the host
computer. Data received from the host computer is stored; this
data is sent to the monitor after you put the terminal back
on-line.
You can only select local from set-up.
The VT220 has four major operating modes. You can select these modes from the keyboard, or from the host via control codes.
VT200 mode, 7-bit controls is the default mode and executes standard ANSI functions. This mode provides the full range of VT220 capabilities in an 8-bit communications environment with 7-bit controls (Chapter 2). This mode supports the DEC multinational character set or national replacement character (NRC) sets, depending on the character set mode selected. You can access both types of character sets from the keyboard, or from the host computer via control codes. This operating mode also provides some backward compatibility for existing VT100 software.
VT200 mode, 8-bit controls executes standard ANSI functions. This mode provides the full range of VT220 capabilities in an 8-bit communications environment with 8-bit controls (Chapter 2). This mode supports the DEC multinational character set or national replacement character (NRC) sets, depending on the character set mode selected. As in VT200 mode, 7-bit controls, you can access both types of character sets from the keyboard or with programmed control codes.
VT100 mode executes standard ANSI functions. It has a high degree of compatibility with Digital's VT102 terminal. (Appendix A describes VT220/VT102 differences). This mode restricts use of the keyboard to VT100 keys. All data is restricted to 7 bits, and only ASCII, national replacement characters (NRC), or special graphics characters are generated. This mode is provided for strict backward compatibility with existing software written for the VT100 terminal family.
VT52 mode executes Digital (DEC) private functions (not ANSI). It has a degree of compatibility with Digital's VT102 terminal operating in a VT52 mode. This mode restricts use of the keyboard to VT52 keys. All data is restricted to 7 bits, and only ASCII, U.K., or special graphics characters are generated.
The VT220 has two character set modes, multinational and national. You can select either mode from the keyboard in set-up, or from the host computer via control codes.
Multinational mode supports the DEC multinational character set (DEC MCS). The DEC MCS is an 8-bit character set that contains most characters used in the major European languages. The ASCII character set is included in the DEC MCS.
National mode supports the national replacement character sets (NRC sets). The NRC sets are a group of eleven 7-bit character sets. The national character set available is determined by the keyboard selected in set-up. Only one national character set is available for use at any one time. National mode restricts compatibility to a 7-bit environment in which the use of the DEC MCS is disabled.