The extended Compaq COBOL options to the ACCEPT and DISPLAY statements provide video forms features. You can develop video forms on VT100 and later series terminals and faithful emulators and write your application without regard to the type of terminal on which the application will eventually run. You can also run your forms application in the terminal emulator window of a workstation. ¹

Using the extended forms of the ACCEPT and DISPLAY statements, you can design video forms to:

• Make data entry applications, menu selections, and special control keys easier to use.
• Clarify the input expected from an operator.
• Improve the appearance of an application's terminal dialog.

Figure 11-1 is a sample form created by a Compaq COBOL program. It is for entry of employee information into a master file. This program prompts the user to type in data. Then the program writes it to the master file and displays a new form.

Figure 11-1 Adding Information to a Master File with a Video Form

For information on differences between the Compaq COBOL and the Compaq COBOL for OpenVMS VAX implementations of screen management, see Appendix B. For complete reference information on the ACCEPT and DISPLAY statements, including syntax, see the Compaq COBOL Reference Manual.

Designing Your Form with ACCEPT and DISPLAY Options

When you design a video form, you can use the ACCEPT and DISPLAY options to do the following:

• Erase specific parts or the entire screen.
• Use relative and absolute cursor positioning.
• Specify video attributes of data to be displayed and accepted.
• Convert data to appropriate usage when accepting or displaying data.
• Handle error conditions when accepting and displaying data.
• Provide screen protection by limiting the number of characters typed on the terminal when accepting data.
• Accept data without echoing.
• Specify default values for ACCEPT statements.
• Define and handle special control keys for ACCEPT statements.
• Allow field editing.

The remainder of this chapter describes these topics.

11.2.1 Clearing a Screen Area

To clear part or all of your screen before you accept or display data, you can use one of the following ERASE options of the ACCEPT and DISPLAY statements:

• ERASE SCREEN---Erase the entire screen before accepting or displaying data at the specified or implied cursor position.
• ERASE LINE---Erase the entire specified line before accepting or displaying data at the specified or implied cursor position.
• ERASE TO END OF SCREEN---Erase from the specified or implied cursor position to the end of the screen before accepting or displaying data at the specified cursor position.
• ERASE TO END OF LINE---Erase from the specified or implied cursor position to the end of the line before accepting or displaying data at the specified cursor position.

These options all work with either absolute or relative cursor positioning. (See Section 11.2.2.)

In Example 11-1, an introductory message is first displayed on the screen (along with a prompt to the user). Then the ERASE SCREEN option causes the entire screen to be erased before "Employee number:" is displayed. Figure 11-2 shows how the screen looks after the ERASE statement executes.

Example 11-1 Erasing a Screen

IDENTIFICATION DIVISION. PROGRAM-ID. ERASEIT. DATA DIVISION. WORKING-STORAGE SECTION. 01 ANY-CHAR PIC X. PROCEDURE DIVISION. A00-BEGIN. DISPLAY "EMPLOYEE ACCESS SYSTEM" LINE 8 COLUMN 30. DISPLAY "Type any character to begin." LINE 20 COLUMN 10. ACCEPT ANY-CHAR. A10-EN-SCREEN. DISPLAY "Employee number:" LINE 4 COLUMN 4 ERASE SCREEN. DISPLAY " " LINE 23 COLUMN 1. STOP RUN.

Figure 11-2 Screen After the ERASE Statement Executes

To position data items at a specified line and column, use the LINE NUMBER and COLUMN NUMBER phrases. You can use these phrases with both the ACCEPT and DISPLAY statements. You can use literals or numeric data items to specify line and column numbers.

In Example 11-2 and in Figure 11-3, "Employee name:" is displayed on line 19 starting in column 4.

Example 11-2 Cursor Positioning

IDENTIFICATION DIVISION. PROGRAM-ID. LOCATE. ENVIRONMENT DIVISION. DATA DIVISION. WORKING-STORAGE SECTION. 01 COL-NUM PIC 99 VALUE 4. PROCEDURE DIVISION. A00-OUT-PARA. DISPLAY "Employee name:" LINE 19 COLUMN COL-NUM ERASE SCREEN. DISPLAY " " LINE 24 COLUMN 1. STOP RUN.

Figure 11-3 Positioning the Data on Line 19, Column 5

If you use LINE, but not COLUMN, data is accepted or displayed at column 1 of the specified line position.

If you use COLUMN, but not LINE, data is accepted or displayed at the current line and specified column position.

If you do not use either phrase, data is accepted or displayed at the position specified by the rules for Format 1 ACCEPT and DISPLAY in the Compaq COBOL Reference Manual.

You can use the PLUS option with the LINE or COLUMN phrases for relative cursor positioning. The PLUS option eliminates the need for counting lines or columns. Cursor positioning is relative to where the cursor is after the previous ACCEPT or DISPLAY. If you use the PLUS option without an integer, PLUS 1 is implied.

To get predictable results from your relative cursor positioning statements, do not:

• Cause a display line to wrap around to the next line.
• Accept data into unprotected fields.
• Go beyond the top or bottom of the screen.
• Mix displays of double-high characters and relative cursor positioning.

In Example 11-3, the PLUS phrase is used twice to show relative positioning, once with an integer, and once without. Figure 11-4 shows the results.

Example 11-3 Using PLUS for Cursor Positioning

IDENTIFICATION DIVISION. PROGRAM-ID. LINEPLUS. PROCEDURE DIVISION. A00-BEGIN. DISPLAY "Positioning Test" LINE 10 COLUMN 20 ERASE SCREEN "Changing Test" LINE PLUS 5 COLUMN PLUS 26 "Adding Test" LINE PLUS COLUMN PLUS 14. DISPLAY " " LINE 23 COLUMN 1. STOP RUN.

Figure 11-4 Cursor Positioning Using the PLUS Option

Depending on your terminal type, you can use one or more of the character attributes in Table 11-1 to highlight your screen data. Example 11-4 shows the use of these attributes in a program segment. Figure 11-5 shows the results of the program segment in Example 11-4.

Table 11-1 Available Character Attributes by Terminal Type

Character Attribute	VT500, VT400, VT300, VT200, and VT100 with Advanced Video Option	VT100 Without Advanced Video Option
BELL Sounds the terminal bell	Available	Available
UNDERLINED Underlines the text	Available	Not Available
BOLD Intensifies the text	Available	Not Available
BLINKING Blinks the text	Available	Not Available
REVERSED Changes the text's foreground & background colors	Available	Not Available

Example 11-4 Using Character Attributes

IDENTIFICATION DIVISION. PROGRAM-ID. CHARATTR. PROCEDURE DIVISION. A00-BEGIN. DISPLAY "Employee No:" UNDERLINED LINE 5 COLUMN 5 ERASE SCREEN. DISPLAY "Employee wage class:" BOLD LINE 5 COLUMN 25. DISPLAY "NAME" BLINKING LINE PLUS 6 COLUMN 6. DISPLAY "SALARY: $" REVERSED LINE PLUS 6 COLUMN 24. DISPLAY " " LINE 23 COLUMN 1.

Figure 11-5 Screen Display with Character Attributes

Use the CONVERSION phrase to convert the value of a numeric data item for display. It causes the value to appear on the screen as follows:

• In DISPLAY usage
• With a decimal point (if needed) or comma (if DECIMAL-POINT IS COMMA)
• Edited (if needed)
• With a sign (if needed)

Thus, the values of non-DISPLAY data items can be converted to a readable form. The size of the displayed field is determined by the PICTURE clause of the displayed item. Example 11-5 and Figure 11-6 show how to display different types of data with the CONVERSION phrase.

Example 11-5 Using the CONVERSION Phrase

IDENTIFICATION DIVISION. PROGRAM-ID. CONVERT. ENVIRONMENT DIVISION. DATA DIVISION. WORKING-STORAGE SECTION. 01 DATA1A PIC X(10). 01 DATA1B PIC X(10) JUST. 01 DATA2 PIC +++++9999.99. 01 DATA3 PIC S9(2)V9(2) COMP. 01 DATA4 PIC S9(3)V9(3) COMP. 01 DATA5 PIC S9(6)V9(6) COMP. 01 DATA6 PIC S9(4)V9(4) COMP-3. 01 DATA7 PIC S9(1)V9(7) SIGN LEADING SEPARATE. PROCEDURE DIVISION. CONVERT-CHECK SECTION. P1. DISPLAY "to begin... press your carriage Return key" LINE 1 COLUMN 1 ERASE SCREEN BELL UNDERLINED REVERSED. ACCEPT DATA1A. DISPLAY "X(10) Test" LINE 8 ERASE LINE. ACCEPT DATA1A WITH CONVERSION PROTECTED REVERSED LINE 8 COLUMN 50. DISPLAY DATA1A REVERSED WITH CONVERSION LINE 8 COLUMN 65. DISPLAY "X(10) JUSTIFIED Test" LINE 10 ERASE LINE. ACCEPT DATA1B WITH CONVERSION PROTECTED REVERSED LINE 10 COLUMN 50. DISPLAY DATA1B REVERSED WITH CONVERSION LINE 10 COLUMN 65. P2. DISPLAY "Num edited Test (+++++9999.99):" LINE 12 ERASE LINE. ACCEPT DATA2 PROTECTED REVERSED WITH CONVERSION LINE 12 COLUMN 50. DISPLAY DATA2 REVERSED WITH CONVERSION LINE 12 COLUMN 65. P3. DISPLAY "Num COMP Test S9(2)V9(2):" LINE 14 ERASE LINE. ACCEPT DATA3 PROTECTED REVERSED WITH CONVERSION LINE 14 COLUMN 50. DISPLAY DATA3 REVERSED WITH CONVERSION LINE 14 COLUMN 65. P4. DISPLAY "Num COMP Test S9(3)V9(3):" LINE 16 ERASE LINE. ACCEPT DATA4 PROTECTED REVERSED WITH CONVERSION LINE 16 COLUMN 50. DISPLAY DATA4 REVERSED WITH CONVERSION LINE 16 COLUMN 65. P5. DISPLAY "Num COMP Test S9(6)V9(6):" LINE 18 ERASE LINE. ACCEPT DATA5 PROTECTED REVERSED WITH CONVERSION LINE 18 COLUMN 50. DISPLAY DATA5 REVERSED WITH CONVERSION LINE 18 COLUMN 65. P6. DISPLAY "Num COMP-3 Test S9(4)V9(4):" LINE 20 ERASE LINE. ACCEPT DATA6 PROTECTED REVERSED WITH CONVERSION LINE 20 COLUMN 50. DISPLAY DATA6 REVERSED WITH CONVERSION LINE 20 COLUMN 65. P7. DISPLAY "Num DISPLAY Test S9(1)V9(7)Sign Lead Sep:" LINE 22 ERASE LINE. ACCEPT DATA7 PROTECTED REVERSED WITH CONVERSION LINE 22 COLUMN 50. DISPLAY DATA7 REVERSED WITH CONVERSION LINE 22 COLUMN 65. P8. DISPLAY "To end...type END" LINE PLUS COLUMN 1 ERASE LINE BELL UNDERLINED REVERSED. ACCEPT DATA1A. IF DATA1A = "END" STOP RUN. GO TO P1.

Figure 11-6 Sample Run of Program CONVERT

Note that, in addition to the items illustrated in Figure 11-6, you can also display the following:

• COMP-1 and COMP-2 data items
• On OpenVMS, RMS registers (RMS-STS, RMS-STV, RMS-FILENAME, RMS-CURRENT-STS, RMS-CURRENT-STV, RMS-CURRENT-FILENAME) <>
• LINAGE-COUNTER register
• RETURN-CODE special register
• RWCS registers (PAGE-COUNTER, LINE-COUNTER)
• VALUE EXTERNAL data items
• POINTER VALUE REFERENCE data items

The /DISPLAY_FORMATTED command-line qualifier is an alternative way to display numeric data without specifying the CONVERSION phrase. It accomplishes the same result, converting any nonprinting values for display. (The default is /NODISPLAY_FORMATTED.)

11.2.5 Handling Data with ACCEPT Options

The ACCEPT options CONVERSION, ON EXCEPTION, PROTECTED, SIZE, NO ECHO, and DEFAULT are described in the following sections.

11.2.5.1 Using CONVERSION with ACCEPT Data

When you use the CONVERSION phrase with an ACCEPT numeric operand (other than floating point), Compaq COBOL converts the data entered on the form to a trailing-signed decimal field. Editing is performed when specified by destination. The data is then moved from the screen to your program using standard MOVE statement rules.

When you use the CONVERSION phrase with an ACCEPT numeric floating-point operand, Compaq COBOL converts input data to floating-point (COMP-1 or COMP-2 as appropriate). The converted result is then moved to the destination as if moving a numeric literal equivalent to the input data with the MOVE statement.

When an ACCEPT operand is not numeric, the CONVERSION phrase moves the input characters as an alphanumeric string, using standard MOVE statement rules. This lets you accept data into an alphanumeric-edited or JUSTIFIED field.

If you use the CONVERSION phrase while accepting numeric data, you can also use the ON EXCEPTION phrase to control data entry errors.

If you do not use the CONVERSION phrase, data is transferred to the destination item according to Format 1 ACCEPT statement rules.

11.2.5.2 Using ON EXCEPTION When Accepting Data with CONVERSION

If you enter illegal numeric data or exceed the PICTURE description (if not protected) of the ACCEPT data (with an overflow to either the left or right of the decimal point), the imperative statement associated with ON EXCEPTION executes, and the destination field does not change.

Example 11-6 (and Figure 11-7) show how the ON EXCEPTION phrase executes if you enter an alphanumeric or a numeric item out of the valid range. The statements following ON EXCEPTION prompt you to try again.

If you do not use ON EXCEPTION and a conversion error occurs:

• The field on the screen is filled with spaces.
• The terminal bell rings and the terminal automatically reprompts you for the data results.

Example 11-6 Using the ON EXCEPTION Phrase

IDENTIFICATION DIVISION. PROGRAM-ID. ONEXC. ENVIRONMENT DIVISION. DATA DIVISION. WORKING-STORAGE SECTION. 01 NUM-DATA PIC S9(3)V9(3) COMP-3. PROCEDURE DIVISION. A00-BEGIN. DISPLAY "Enter any number in this range: -999.999 to +999.999" LINE 10 COLUMN 1 ERASE SCREEN. ACCEPT NUM-DATA WITH CONVERSION LINE 15 COLUMN 16 ON EXCEPTION DISPLAY "Valid range is: -999.999 to +999.999" LINE 20 REVERSED WITH BELL ERASE TO END OF SCREEN DISPLAY "PLEASE try again... press your carriage return key to continue" LINE PLUS REVERSED ACCEPT NUM-DATA GO TO A00-BEGIN. STOP RUN.

Figure 11-7 Accepting Data with the ON EXCEPTION Option

A DISPLAY statement within an ACCEPT [NOT] ON EXCEPTION statement must be terminated, with, for example, END-DISPLAY.

11.2.5.3 Protecting the Screen

You can use the PROTECTED phrase in an ACCEPT statement to limit the number of characters that can be entered. This phrase prevents overwriting or deleting parts of the screen. For more information about using the PROTECTED phrase, refer to the ACCEPT statement in the Compaq COBOL Reference Manual.

If you use this phrase, and you try to type past the rightmost position of the input field or delete past the left edge of the input field, the terminal bell sounds and the screen cursor does not move. You can accept the data on the screen by pressing a legal terminator key, or you can delete the data by pressing the DELETE key. If you specify PROTECTED WITH AUTOTERMINATE, the ACCEPT operation terminates when the maximum number of characters has been entered unless a terminator has been entered prior to this point. For more information on legal terminator keys, refer to the CONTROL KEY phrase of the ACCEPT statement in the Compaq COBOL Reference Manual.

You can also use the REVERSED, BOLD, BLINKING, or UNDERLINED attributes with the PROTECTED phrase. Using these attributes lets you see the size of the input field on the screen before you enter data. The characters you enter also echo the specified attribute.

You can specify the NO BLANK and FILLER phrases with the PROTECTED phrase. The NO BLANK phrase specifies that the protected input field is not to be filled with spaces until after the first character is entered. The FILLER phrase initializes each character position of the input field with the filler character specified.

When you use the FILLER phrase with the NO BLANK phrase, the input field is filled with the filler character only after you have entered the first character.

The PROTECTED SIZE phrase sets the size of the input field on the screen and allows you to change the size of the input field from the size indicated by the PICTURE phrase of the destination item. Example 11-7 and Figure 11-8 show how to use the SIZE phrase with the PROTECTED phrase. When the example specifies SIZE 3, any attempt to enter more than three characters makes the terminal bell ring. When the example specifies SIZE 10, the ACCEPT statement includes the ON EXCEPTION phrase to warn you whenever you enter a number that will result in truncation at either end of the assumed decimal point. Figure 11-8 shows such an example in which the operator entered a 10-digit number, exceeding the storage capacity of the data item NUM-DATA on the left side of the assumed decimal point.

Example 11-7 Using the SIZE and PROTECTED Phrases

IDENTIFICATION DIVISION. PROGRAM-ID. PROTECT. ENVIRONMENT DIVISION. DATA DIVISION. WORKING-STORAGE SECTION. 01 NUM-DATA PIC S9(9)V9(9) COMP-3. PROCEDURE DIVISION. A00-BEGIN. DISPLAY "Enter data item (NUM-DATA) but SIZE = 3:" LINE 1 COLUMN 14 UNDERLINED ERASE SCREEN. PERFORM ACCEPT-THREE 5 TIMES. DISPLAY "Same data item (NUM-DATA) BUT SIZE = 10:" LINE PLUS 3 COLUMN 14 UNDERLINED. PERFORM ACCEPT-TEN 5 TIMES. STOP RUN. ACCEPT-THREE. ACCEPT NUM-DATA WITH CONVERSION PROTECTED SIZE 3 LINE PLUS COLUMN 14. ACCEPT-TEN. ACCEPT NUM-DATA WITH CONVERSION PROTECTED SIZE 10 LINE PLUS COLUMN 14 ON EXCEPTION DISPLAY "TOO MANY NUMBERS--try this one again!!!" COLUMN PLUS REVERSED GO TO ACCEPT-TEN.

Figure 11-8 Screen Display of NUM-DATA Using the PROTECTED Option

When you do not use the PROTECTED phrase, the amount of data transferred is determined according to the ACCEPT statement rules. (See the Compaq COBOL Reference Manual.)