Running a program

About this task

Clear the screen before running an exec. If you want to run a program that has a file type of EXEC, you type in REXX followed by its file name. In this case, type rexx hello on the command line and press Enter. Try it!

Suppose your name is Sam. Type sam and press Enter. Hello SAM is displayed.

rexx hello
Hello! What is your name?
sam
Hello SAM

Here is what happens:

The SAY instruction displays Hello! What is your name?
The PULL instruction pauses the program, waiting for a reply.
You type sam on the command line and then press Enter.
The PULL instruction puts the word SAM into the variable (the place in the computer's storage) called who.
The IF instruction asks, Is who equal to nothing?
```
who = ""
```
This means, is the value stored in who equal to nothing? To find out, REXX substitutes that stored value for the variable name. So the question now is: Is SAM equal to nothing?
```
"SAM" = ""
```
Not true. The instruction after then is not processed. Instead, REXX processes the instruction after else.
The SAY instruction displays "Hello" who , which is evaluated as
```
Hello SAM
```

Now, here is what happens if you press Enter without typing a response first.

hello
Hello! What is your name?

Hello stranger!

Then again, maybe you did not understand that you had to type in your name. (Perhaps the program should make your part clearer.) Anyhow, if you just press Enter instead of typing a name:

The PULL instruction puts "" (nothing) into the place in the computer's storage called who.
Again, the IF instruction tests the variable
```
who = ""
```
meaning: Is the value of who equal to nothing? When the value of who is substituted, this scans as:
```
"" = ""
```
And this time, it is true.
So the instruction after then is processed, and the instruction after else is not.