ECHO in COBOL

Learn about the ECHO feature in COBOL, including its usage in terminal interaction, input handling, and screen management.

Understanding ECHO

ECHO is a terminal interaction feature in COBOL that controls whether characters typed during ACCEPT operations are displayed on the screen. This feature is essential for creating secure input interfaces and managing how user input is handled visually.

Key Characteristics

  • Controls character display during input
  • Can be enabled or disabled per ACCEPT statement
  • Commonly used for password input
  • Part of COBOL's screen handling capabilities

Basic ECHO Usage

Standard Input with ECHO

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       WORKING-STORAGE SECTION.
       01  USER-INPUT    PIC X(20).
       
       PROCEDURE DIVISION.
           DISPLAY "Enter your name: "
           ACCEPT USER-INPUT
           DISPLAY "Hello, " USER-INPUT

Input without ECHO

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       WORKING-STORAGE SECTION.
       01  PASSWORD    PIC X(20).
       
       PROCEDURE DIVISION.
           DISPLAY "Enter password: "
           ACCEPT PASSWORD WITH NO ECHO
           DISPLAY "Password accepted"

Advanced ECHO Applications

Custom Input Masking

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       WORKING-STORAGE SECTION.
       01  SECURE-INPUT    PIC X(10).
       01  DISPLAY-MASK    PIC X(10).
       
       PROCEDURE DIVISION.
           INITIALIZE DISPLAY-MASK
           DISPLAY "Enter PIN: "
           ACCEPT SECURE-INPUT WITH NO ECHO
           PERFORM VARYING WS-I FROM 1 BY 1
                   UNTIL WS-I > LENGTH OF SECURE-INPUT
               MOVE "*" TO DISPLAY-MASK(WS-I:1)
           END-PERFORM
           DISPLAY "Input received: " DISPLAY-MASK

Screen Section Implementation

ECHO can be used effectively with COBOL's SCREEN SECTION for more sophisticated input handling:

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       SCREEN SECTION.
       01  LOGIN-SCREEN.
           05  BLANK SCREEN.
           05  LINE 5 COLUMN 10 VALUE "Username: ".
           05  LINE 5 COLUMN 20 PIC X(20)
               USING WS-USERNAME.
           05  LINE 6 COLUMN 10 VALUE "Password: ".
           05  LINE 6 COLUMN 20 PIC X(20)
               USING WS-PASSWORD
               SECURE.

Handling Special Cases

Mixed ECHO States

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       WORKING-STORAGE SECTION.
       01  PUBLIC-DATA     PIC X(20).
       01  PRIVATE-DATA    PIC X(20).
       
       PROCEDURE DIVISION.
           DISPLAY "Enter public info: "
           ACCEPT PUBLIC-DATA
           
           DISPLAY "Enter private info: "
           ACCEPT PRIVATE-DATA WITH NO ECHO
           
           DISPLAY "Public: " PUBLIC-DATA
           DISPLAY "Private data received (hidden)"

Best Practices

  • Always use NO ECHO for sensitive data input
  • Provide clear user feedback when input is hidden
  • Consider platform-specific behavior
  • Test ECHO functionality thoroughly
  • Combine with other security measures

Common ECHO Patterns

Password Validation

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       WORKING-STORAGE SECTION.
       01  WS-PASSWORD     PIC X(20).
       01  WS-CONFIRM      PIC X(20).
       01  WS-MATCH        PIC X VALUE 'N'.
       
       PROCEDURE DIVISION.
           PERFORM UNTIL WS-MATCH = 'Y'
               DISPLAY "Enter password: "
               ACCEPT WS-PASSWORD WITH NO ECHO
               DISPLAY "Confirm password: "
               ACCEPT WS-CONFIRM WITH NO ECHO
               IF WS-PASSWORD = WS-CONFIRM
                   MOVE 'Y' TO WS-MATCH
                   DISPLAY "Passwords match"
               ELSE
                   DISPLAY "Passwords do not match, try again"
               END-IF
           END-PERFORM

Error Handling

  • Handle unexpected input gracefully
  • Provide clear error messages
  • Implement input validation
  • Consider timeout scenarios
  • Plan for system interrupts

Frequently Asked Questions

Related Pages

Related Concepts

Terminal Interaction

Understanding how COBOL programs interact with terminal devices and handle user input

Screen Handling

Techniques for managing screen output and user interface in COBOL applications

Input Validation

Methods for validating and processing user input in COBOL programs