Instructions

An instruction tells the system to do something. Instructions can contain one or more assignments, labels, or commands and they usually start on a new line. The following are explanations of some of the more common instructions.

SAY Instruction - The format for the SAY instruction is:

SAY expression

The expression can be something you want displayed on the screen or something to be computed, such as an equation:

SAY 5 + 6 "= eleven"

This displays

11 = eleven

With the SAY instruction, anything not in quotation marks is changed to uppercase or is processed. If you want something to appear exactly as it is typed, enclose it in quotation marks.

PULL and PARSE PULL Instructions -

In a procedure, the usual sequence of instructions is to use SAY to ask a question and PULL to receive the answer. The response typed by the user is put into system memory. The following procedure does not work correctly if the PULL instruction comes before the SAY instruction.

Question: What do you think happens when the following procedure, NAME.CMD, is run?

/* Using the PULL Instruction */
SAY "Enter your name"
PULL name          /* Puts response
from user into memory */
SAY "Hello" name
EXIT

Answer: NAME.CMD puts a name in memory and then displays that name anywhere in the file that the word name appears without the protection of single or double quotation marks.

If you tried the NAME procedure, you probably noticed that your name was changed to uppercase. To keep the characters as you type them, use the PARSE PULL instruction. Here is an example called CHITCHAT.CMD that uses the PARSE PULL instruction:

/* Using the PARSE PULL Instruction */
SAY "Hello! Are you still there?"
SAY "I forgot your name.  What is it?"
PARSE PULL name
SAY name "Are you going to Richard's seminar?"
PULL answer
IF answer = "YES"
 THEN
 SAY "Good.  See you there!"
IF answer = "NO"
 THEN
 SAY "Sorry,  We will miss your input."
EXIT

EXIT Instruction

The EXIT instruction tells the procedure to end. The EXIT instruction should be used in a procedure that contains subroutines. Although the EXIT instruction is optional in some procedures, it is good programming practice to use it at the end of every procedure.