HALT command
Summary
- Privileges
- User 0
- Function
- Suspends the reading of User 0's input
Syntax
HALT [n1,message[,n2,reply]
Where:
| n1 | is the number of characters in the message. The maximum number of characters for n1 is 72. |
|---|---|
| message | is the text of the message that is displayed on the operator's console when the HALT is executed. If a message is not specified, WAITING is the default. |
| n2 | is the number of characters in the reply. The maximum number of characters for n2 is 28. |
| reply | is the text of the reply that is expected from the operator. The operator must enter either this reply or one of the operator commands listed in the beginning of this section on the discussion of types of users. If a reply if not specified, WAITING is the default. |
All leading and intermediate spaces must be accounted for in the length counts.
Example
HALT 14,UP AND RUNNING,8,CARRY ON
Usage notes
- The HALT command indefinitely suspends the reading of User 0's input, but it does not affect other users in the same job. HALT is useful in controlling input after initial run processing and before the start of Online processing.
- If the HALT command is executed, it writes a message to the operator's console and causes the user issuing the HALT to wait for a reply from the operator. ONLINE processing is described in detail in Controlling system operations (CCAIN).
- If the HALT command shown in the example above is executed, a message in the following form appears on the operator's console:
xx jobname ** 000 ** UP AND RUNNING
xx represents the system-assigned message number to which the operator must reply in order for User 0 to resume reading input lines. Reading cannot resume until the operator enters an operator command or issues an entry in the following form:
R xx,CARRY ON
If you respond incorrectly, Model 204 prompts again.
- The processing of the HALT command occurs in a way that changes the priority of the command's issuer (User 0). The priority is set to one above the maximum priority of a HIGH user; that is, the minimum, maximum, and current priorities are set to 128. This allows User 0 the highest possible dispatching priority of any Model 204 user. When the HALT command has completed execution, User 0's priority is reset to the settings that were in effect prior to issuing the HALT command.
Handling an incorrect message length
The HALT command issues a Command Rejected message, if the length specified for the message or reply is not of the correct length. This is an upward incompatibility. Formerly the message and reply defaulted to WAITING, if the length of the actual message was greater than specified.
In addition, to break out of the HALT wait, the reply given must match exactly the reply specified or the default reply. This represents another upward incompatibility. Formerly, the number of characters compared was the number specified in the HALT command regardless of the length of the actual reply string. If the reply ends in a blank, then the reply issued must include a blank followed by a semicolon (;).