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[page 54]
The STOP Command
The STOP command is used to specify a halt in the object program. Its general form is simply:
STOP n
where n is an integer.
The number n will be displayed when the command is executed, i.e., when the machine halts. Restarting the machine causes execution of the object program to be resumed beginning with the next command in sequence.
For a "dead-end" halt, an unconditional GO TO command placed immediately following the STOP can be used to effect a transfer back to the STOP command.
Other Program Commands
In addition to the commands described in the foregoing pages there are two program commands that do not fall into any of the four categories discussed. These "miscellaneous" commands, which employ the verbs LOAD and DISPLAY, are described in the following paragraphs:
The LOAD Command
Since an object program may exceed the capacity of internal storage, a facility is needed for keeping a part of the program in "standby status" (in external storage) and for calling it in to replace a portion of the program currently in internal storage. The LOAD command, used in conjunction with the processor command OVERLAP, provides this facility. The general form of the LOAD command is:
LOAD procedure.name
where "procedure.name" is the name of a portion of the program which, at object time, will be waiting in external storage. The LOAD command causes this unit of procedure to be brought into the area of storage shared by the procedures mentioned in the associated OVERLAP command. The portion of the object program formerly occupying that area is replaced by the new portion but can be retrieved later by another LOAD command.
Any unit of procedure addressed by a LOAD command must be named in an OVERLAP command.
The use of the LOAD command is illustrated in the example given in the discussion of the OVERLAP command (see page 56).
The DISPLAY Command
At certain times during the running of the object program, the programmer may wish to examine particular values of data in internal storage, or may need to send messages to the operator. The DISPLAY command causes the object program to present such low-volume information on an appropriate output device or display medium. The general form of the DISPLAY command is:
DISPLAY 'any message' data.name 'any message'
The DISPLAY command displays all the information that follows the word DISPLAY up to, but not including, a comma or period not enclosed in quotation marks.