Always open on my desktop…

April 28, 2020 Leave a comment


Categories: Coding

Linux, Windows and related fun…

April 25, 2020 Leave a comment

So let me make this clear. I am NO Linux expert, in fact I barely touch it. I have a web server running an old version of SuseLinux under my desk that I NEVER touch. The web site is just static pages, easily updated simply by replacing them and it works so why mess with something that is not broken!

That said, my wife recently ‘donated’ here old desktop PC to me as she was not using it any more. It’s a decent machine (DELL) but running Windows 10 it was sooooo sloooooow it was painful to use. So I decided to put Linux on it as I had something that I wanted to run on it long term and the problem with Windows is that, in its wisdom it periodically just updates itself and reboots the PC.

So, I downloaded the latest OpenSuse iso, burnt a CD and installed it. Well, after about two days of fighting with it, I installed it!. Most of the installs were because I’d configure it, decide that was not what I wanted (Figuring out which desktop to use was the worst, settled on Gnome in the end but only after about four different attempts at the install) and so it was just easier to wipe it al out and start again.


So, now to the whole point of this post.  My workspace is pretty large (it’s actually made from a kitchen counter top) but also pretty cluttered so having yet another screen, mouse and keyboard on there was not really an option.

My primary monitor had a spare VGA input so I used that but I still had to switch the display over and put the mouse/keyboard on my desk while I used the Linux box and picking up the wrong mouse or typing on the wrong keyboard soon got annoying.

So I looked into remote access.

At first I looked at using X11 but after a lot of messing and experimenting I decided it was messy to set up, still needed a lot of knowledge to use and really only brought individual apps over to the Windows desktop, not the whole Gnome desktop. I am no power user so I need all the help I can get and configurig individual Linux apps to run via X11 on my Windows desktop just seemed like a lot of extra work!

So I opted for VNC which gives you the full desktop experience.

Now you’d think that this would be easy and like all things, once you know how, it is but getting to that stage still took a couple of days! So this is the output from that ‘learning’ experience.

I am running Windows 10 and OpenSuse Leap 15.1 so this information should work for that configuration but like all software, as it moves forward (for better or worse!) who knows how long it will stay valid. Still…

One Time Setup Stuff

So first off, on the Linux box, using Yast, in in Network Services Remote Administration (VNC) , I set:

Allow Remote Administration with Session Management
The alternative was:
Allow Remote Administration without Session Management

I have no idea how that changes things, except perhaps in relation to sessions staying active when I disconnect the remote VNC session.

So then I used Putty on the Windows box to connect to my Linux box, LINBOX:

I set:

Hostname LINBOX Port 22
Under Connection:SSH:Tunnels add
Source port 5901
Destination LBOX:5901

I then saved that as a profile for future use.


I needed to do this next bit because up to this point, I could connect with VNC to my Linux desktop but all I got was a black screen. So for this next bit of the setup I needed to edit a file on the Linux box as a root user but rather than login as root, apparently never a good idea, I logged in as myself then did the following:

sudo vncserver                      This will start session with ROOT authority (enter root password when prompted)
Note session number or use vncserver -list to list sessions numbers (should be only one at this stage!)

Back on Windows I launched my VNC viewer (Tightvnc in my case) using host:port (so it was LINBOX:2) in my case
You will connect as root so enter root password when/if prompted.

This put me into my Gnome desktop on the Linux box.

I then selected the files application from the application pull down on the desktop menu and navigated to:


I then right clicked on custom.conf and selected edit (so you are now editing this file as a root user).

Locate [xdmcp] and just below it add this line:

Then save the file, exit the files application and
logoff as root (top right corner of screen)
End vnc session (close the widow)

Now back in the putty command window, restart xdm by entering:

sudo systemctl restart xdm

Now kill that vncserver process (the one that was using root) with

vncserver -kill :n n was 2 in my case (see above)

And that’s it for the one time setup stuff.


Regular Logon

You should now be able to VNC as a regular user to your desktop (Gnome in my case) as a regular user as follows:

Start putty as before and select the same LINBOX config options

Hostname LINBOX Port 22
Under Connection:SSH:Tunnels add
Source port 5901
Destination P390:5901

Login with your user id and password
vncserver This will start session as a normal user. NOTE NO SUDO command before vncserver.
Note session number or use vncserver -list to list sessions

Launch VNC Viewer or Tightvnc using host:port (so LINBOX:3 if the session number from vncserver was 3)
Enter YOUR password if required

And you should be good to go!!!

Also note that at this point you can close the putty window (type exit) and your VNC session will still work.

You can also just close the VNC window and come back to it later and it’s all still there, with apps open etc. No need to do the putty/vncserver steps, just use the same session number as before.

When you area ‘really’ done on your Linus desktop, open a putty window to your server as before and type:

vncserver -kill :n

Where n is the session number you were using. This will get rid of the background process.

I installed Regina Rexx and wrote a little exc to automate a lot of the regular logon stuff. It’s not perfect because it has hard coded passwords in it and currently only establishes a new session, cannot reuse an old one but it’s a start (and fun to figure out how to do anyway!)

I believe you can get around the hard coded password problem by setting up certificates to authenticate the session/user but that’s way beyond me at this point in time.


Here’s my (suspended) Linux Gnome desktop in a VNC window on my Windows desktop.






Categories: Uncategorized

Backup a bit…

April 11, 2020 Leave a comment

About a million years ago, actually 1976, I started in the computer industry as an operator. My job interview was with the managing director of the ‘computer department’ because it wasn’t ‘Information Technology’ yet! One thing that I have always remembered from that interview is him saying that I shouldn’t worry about making mistakes because it can always be fixed. I think he probably said it as much to reassure my novice self as anything else, but it always stuck with me.

And for the most part, he was right. But I have to qualify the general statement by saying that fixing it is a lot easier if you’ve got a backup of everything!

This comes to mind because a backup saved my bacon a few days ago.

I’ve been working on a little side project for a good while now, just a fun little thing I’ve been playing around with and while it’s not a lot of code as such, it is pretty involved. Now I still work quite a bit on a good old green screen in ISPF where I tend to use the 3.4 data set list option because I can easily switch from browse of a member to edit and back without having to switch ISPF screens.

The one thing I have never liked about the data set list function and the resultant member list display for a data set though, is that you can easily enter a D (for delete!) against either a data set or member. While it does prompt you to confirm the action (unless you’ve turned it off) it is pretty easy to be not paying attention, press enter on the confirm screen and it’s gone.

At this point you go ‘Oh F***k’ or words to that effect.

I know this because that’s exactly what happened to me the other day. Not paying attention, something popped up, I hit enter and it was only when the word ‘deleted’ appeared beside the member name that I realized I’d screwed up!


Now I’ve been working on this project for a while. In fact I last touched it a few years ago, got to a ‘sticky’ point where the coding was neither fun nor easy and put it aside until recently when I decided to pick it up again.

In all that time I kept thinking I really should start taking backups of the work. Fortunately for me, that’s exactly what I had done the previous day. I spent some time to write some jobs to back everything up so when I screwed up, thankfully I had a backup that I was able to restore the missing member from.

Had this happened a day earlier and it would have been a whole different story.

An after effect of this is that I wrote my own little data set list function that does NOT allow me to do a delete either against the data set or a data set member. Again, this was something I’ve often thought about, just never gotten around to until this happened and I got ‘motivated’ as it were.

My ISPF 3.4 alternative can be down loaded from ===> here. <===

Unzip the file and upload the exec and panel to your ISPF REXX and ISPPLIB panel library using a text transfer to convert back to EBCDIC. Edit the exec to specify the name of the panel library or remove the LIBDEFs for the panel library if it is already allocated to your ISPF ISPPLIB DD.

Then just run the exec, @34. It takes two parameters:

  • A mask to specify the datasets to list, just like the real 3.4
  • One or more exclude strings. Any data set name in the result list that matches one of these strings will not be show.

Line commands against data sets are:

  • B or S – Browse
  • E – Edit
  • Z – Compress

Line commands against a member in a member list are:

  • S – Whatever what entered against the data set, E or B.
  • E – Edit
  • B – Browse
  • SUB – Submit the member
  • =  Repeat the previous command


It’s very basic. A lot of the error messages are just issued as say statements. If you use it, feel free to modify it to your needs.

This is the exec source:

/* rexx */
/* Custom ISPF 3.4 function */
/* pfx is dataset prefix to list */
/* excl is one or more exclude masks */
/* David E Ellis April 2020 */

parse arg pfx excl
if pfx = '' then pfx = sysvar(syspref)

address ISPEXEC



if rc <> 0 then do
say "TBCREATE RC="rc
signal exit

if rc <> 0 then signal exit

do forever
'TBTOP @34'
'TBDISPL @34 PANEL(@34)' ,

if rc > 7 then leave

if row = 0 then row=1

do ztdsels

if sel <> '' then do
upper sel
when sel='S' then do
rc=doit('B') /* default */
when sel='B' then do
when sel='E' then do
when sel='Z' then do
otherwise do
zerrsm = 'Invalid option'
zerrlm = 'Invalid option for this line'
zerralrm = 'NO'

end /* if sel <> '' */

if ztdsels = 1 then iterate

end /* do ztdsels */


"TBEND @34"
return 0

parse arg pfx

if rc <> 0 then do
say "LMDINIT RC="rc
signal Build_list_exit

DSN = ''
do forever
if rc = 4 then do
say 'Nothing found for 'pfx
if rc = 8 then leave /* end of list */
if rc <> 0 then do
say "LMDLIST RC="rc

exclrc=0 /* RC=0 means do NOT exclude */
if excl<>'' then do
if exclrc=0 then do
"TBADD @34"

return myrc

parse arg option

if strip(dstype) = "" then do /* unknow org, let ispf handle */
option" DATASET('"dsname"')"
signal doit_exit

return myrc

parse arg mlistopt
/* mlistopt just controls default action if S entered for mbr */

if rc<>0 then do
say "LMINIT Rc="rc
signal mlist_exit

if rc<>0 then do
say "LMOPEN Rc="rc
signal mlist_exit

do forever


"TOP("mbr") FIELD(9)"
if rc=0 then nop
if rc=4 then do
say " Empty dataset"
if rc=8 then leave
else do


do forever
if getrc=0 then nop
if getrc=8 then leave
else do
say "LMMDISP GET RC="getrc



return myrc

procmbr: Procedure Expose mlistopt dsname prevcmd
parse arg mbr,cmd

if cmd = "S" then do
if cmd = "B" then do
"BROWSE DATASET('"dsname"("mbr")')"
if cmd = "E" then do
"EDIT DATASET('"dsname"("mbr")')"
if cmd = "SUB" then do
address TSO "SUBMIT ('"dsname"("mbr")')"
if cmd = "=" then do
else do
say "Invalid command "cmd

return 0

CheckExcl: Procedure
/* If any of the string in excl are in the dsn return rc=4 */
/* else returns rc=0 (excl strigs NOT in dsn) */

parse arg dsn , excl
upper dsn
upper excl

do i = 1 to words(excl)
if pos(word(excl,i),dsn) > 0 then return 4

return 0

compress: Procedure
parse arg dsname, dstype

if dstype <> 'PDS' then do
say 'Invalid dataset type'
signal compress_exit

if rc <> 0 then do
say "LMINIT RC="rc
signal compress_exit

"LMCOMP DATAID("lmiid")"
if rc=0 then do
say "Compressed"
else do
say "LMCOMP RC="rc

"LMFREE DATAID("lmiid")"

return 0


And this is the panel definition:

%--/-/-- Dataset List --/-/--
%Command ==> _ZCMD / / +Scroll ===>_ZAMT+

+DSLIST - Data Sets Matching@Z +

_Z+ @Z +

IF (.MSG = ' ')
&SEL = ' '

IF (&ZTDSELS ^= 0000)
VER (&SEL, LIST, B, b, E , e , S , s, Z, z)







Categories: Mainframe

Optional Instructions…!

April 8, 2019 Leave a comment

One great thing about the development of the IBM mainframe hardware of the last few years has been the addition of lots of nice new, shiny instructions especially those that allow for the use of all or part of the ‘grande’, I.E. 64 bit, registers. For example, to do a locked update on a double word (8 bytes) in the past you would need to use two pairs of registers, for example, zero and one and fourteen and fifteen and use a Compare Double and Swap (CDS) instruction to do the update. Oh, and those pairs of registers had to be even-odd  as well. Now you can just use two 64 bit registers and use a Compares and Swap Grande (CSG) instruction to do the update and the registers do not need to be an even-odd pair either.

Basically, code that used to take several instructions and registers can often be simplified into fewer instructions and use less registers by using the newer instructions from the instruction set. The benefit is less CPU time consumed and faster execution.

This is great and I’ve been doing this sort of thing for a good few years now. However, if you read the POP (Principles of Operation) you may notice next to some instructions under the ‘Program Exceptions’ heading something along the lines of:

  • Operation (if …… facility is not installed)

What this means is that this instruction is ‘optional! What that means is that it may not be physically implemented on the machine and what that means is that if you try to execute it, you will get an operation exception (S0C1 abend).

There are fields in the PSA you can test to see if a facility is installed before attempting to use an instruction or feature of the hardware but to be honest, in all my forty some years of coding, I have never had to do that…..Until now.

Well, actually, not even now which I will explain in a minute.

I wrote some code recently and wanted to do a divide. Because of the size of the numbers, I used the grande version of the divide instruction. Before doing the divide I needed to clear the high word of the registers so I used the SHHHR Subtract High instruction.

This worked great on my test machine but failed on another machine with an S0C1 abend. Yep, that other machine did not have the high-word feature installed.

It was easy enough to replace the instruction with another (The ICMH version of Insert Character under Mask) which is not feature based and so should be there on all hardware but this is the first time in all my years of coding that I’ve ever had to even consider to availability of a feature.

I’ve always thought of the instruction set in the machine as being like an engine in a car, every car has an engine, but I’ve never really considered that not all car engines are the same. If you want more power, it typically costs more to buy a car with a more powerful engine. A more powerful car will (speed limits aside) get you from A to B more quickly and if time is money, spending money up front to get a more powerful car will save you time (and money) later on. In the computer world, you can pay more up front to buy a machine with more features (better instruction set) and get faster execution which save CPU time and thus chargeable MSUs or you can pay less and pay the money when you consume the extra MSUs due to the smaller and thus slower instruction set available to code running on the machine.

In my case, rather than test to see if the feature (instruction) was available before using it I just replaced it with an instruction that I know will always be there. This reason for this is that this is very low use code and it was two instances of one instruction. It would take longer to execute the code to test for the feature and branch to alternate code than it would to just always just execute an alternative instruction. That test and branch also adds slightly more complexity to the code which adds to the possibility of errors and makes it just that bit harder to maintain.

Had the block of code been high use and/or very complex it may have been worth while to test for the feature and use the faster instructions/simpler code when available but that was not the case here. Simple is good in my book!


Categories: Uncategorized

A Matter of Style – Labels…

November 9, 2017 Leave a comment

As much as possible I try to make it obvious from a variable label, what type of variable it is and wherever possible, what other variable or control block it is related to.


I start variable names for constants with a # sign, thus:


If a variable starting with a # sign is on the receiving end of an instruction, it is wrong because I should not be modifying constants!


I start equated value names with an @ sign, thus:

@ONE   EQU   1
@FLAG1 EQU   X'80'

For equated symbols that define a length, I add the suffix ‘_LEN’ to the symbol name, thus:

FIELD1      DS    CL8

That way, it is obvious in the code that I am referring to an equated length value, for example:

          LA    R1,@FIELD1_LEN        Get field length in R1

It it obvious that I intend to load the field length and not the field address into the register but having the _LEN suffix ensures that I get the length and do not accidentally code the field address instead.

Equate/Field relationship

I prefer to ‘tie’ equated values for a field to the field they relate to by using a naming convention that uses the field name as part of the equate symbol, thus:

FIELD1         DS  C

Then in code I would write something like this:

          CLI   FIELD1,@FIELD1_YES
          BE   DO_YES
          CLI   FIELD1,@FIELD1_NO
          BE   DO_NO
          B     NOT_SET


Similar code would apply to setting the field value, only use equated symbols that are related to the target field. This convention ensures that you are only setting and testing for values actually defined for the field.

About the only exception to this rule that I use is the use of the following common equated symbols:

@YES    EQU   C'Y'
@NO     EQU   C'N'

@YES and @NO should be obvious, @POSTED is to test an ECB posted bit flag,E.G:

          TM    ECB1,@POSTED           Is ECB posted?
          BO    DONE


Field/DSECT relationship

When I am creating my own DSECTS I prefer to prefix the name of each field within the DSECT with the DSECT name and an underscore, thus:


Using this standard makes it easy when reading source code to determine who owns a field. There is no confusion. The length equate for the control block also follows my convention of adding _LEN to the end and prefixing the equate symbol with an @ sign to avoid ambiguity in the executable code.

The exception to the rule…

I do allow for one exception to this rule though and that is for a program’s working storage. Typically I prefix working storage fields with the prefix STG_ (short for ‘storage’) although you can use anything you want, to identify working storage fields, for example W_ etc. It is preferable to use the underscore as part of the name to avoid situations where a field name ‘might’ happen to start with whatever prefix you are using. For example if you use just W as your working storage field prefix, is WORKF1 a field in your working storage or somewhere else? Using this convention, STG_WORKF1 or W_WORKF1 are obviously part of the code’s working storage. And again, the convention ensures that you are using the field you intend and not a WORK1 field defined somewhere else that might allow the program to assemble but my then fail at execution time because the storage it refers to is not addressable or it is addressable but it’s the wrong field and messes up some other code (good luck finding that one!).


Whatever conventions you use, the aim is to make it less likely to introduce errors when developing the code and to make it much easier to read, and locate field owners several months later when someone else has to try to follow, understand and debug or modify your code.





Categories: Coding, Style

A Matter of Style…

November 9, 2017 Leave a comment

There are probably as many ways to write a program as there are programmers in the world, more if you accept that a program is solution or part thereof, to a problem and could be written in more than one language, each of which causes the writer to adopt differing styles.

So basically, there’s more than one way to skin a cat!

Now I’m not saying that the style of assembler programming that I have developed over the years is the best but I think it satisfies many of the requirements that I will cover in what I hope will be a short series of articles. Let’s put it this way, unless someone tells me different, I’ll tend to try to influence any code that I work in towards my preferred style although there are reasons for NOT doing that, for example to maintain the existing style or coding standards since a mix can make things worse.

SO! Why is style important?

Sometimes it isn’t. You may need to write a quick, one off, one use program to solve a problem. As long as it does the job, does style really matter? Well, it depends. If the code is simple then probably not but what if the code is complex? Then making the code at least readable and logical makes sense since if you get it wrong the first time through, it will be a lot easier to diagnose the problem and correct the code.

But let’s consider the more common situation where you are developing a program or even multiple programs that form a piece of software and those programs are for use by paying customers. In other words you are creating commercial software. I am also including software written for in house use (in the business sense) because such development, use and support usually involves internal billing and thus still qualifies it as commercial software.

Basically, if someone else other than the developer or developing department uses it, you can consider it to be commercial software in my mind.

So let’s say that you are assigned the task of developing a z/OS super widget application which, because it uses lots of system services will be written in assembler, or at least a lot of it will be. Let’s looks at how programming style will affect it’s life cycle.


The faster you can develop and test the code to the point where it does what the requirements require without failing or causing other problems, the faster the product will reach the market and thus generate revenue for the business.

Everyone probably has a standard program entry and exit macro and possibly similar ones for subroutine entry and exit but what about other stuff. Parsing of input for example? Do you do it with hard coded assembler or use a macro or service to do parsing in a standard and consistent manner? If a service, do you call that service using a macro to make coding the call simpler and standard? Or, do you let your programmers set everything up by hand (guess which is the more reliable method)?

Do you use a standard form of label name for program labels and subroutine names? Are you still stuck in the ‘all labels must be 8 characters long’ mental state or do you use longer and more meaningful names, either CamelCase or with parts separated by underscores, E.G. WORK_FIELD_1.

Do you use naming standards to tie equated symbols to the field they relate to or is it a free for all. Is it easy to tell, without looking at the variable definition,  if a variable name is a label or an equated value and if a label, is it easy to tell which control block it belongs to, or if a constant, is it easy to tell that it is a constant?

And most importantly in my mind, do you create comment blocks for the program as a whole and for each subroutine that describes the program, it’s inputs, outputs and return codes and the same for all subroutines? Also, if the program is reliant upon a particular control block structure, do you document that WITHIN the code as best you can (using good old EBCDIC character graphics if need be) so that the architecture is right there in the code, not lost on some hard drive somewhere that got wiped because someone didn’t realize that what was on it was needed (the ‘not my job’ syndrome!).


If the code is well structured, follows consistent  naming standards, uses macros to standardize the coding of interface, has proper comments describing what each routine does, what it’s input and outputs are then understanding the code and diagnosing a problem becomes a lot easier and more importantly faster. You are also more likely to be able to correctly fix any problem without introducing new problems. All the above result in a faster turn around time for the resolution of any code related problems. They also mean it is much easier for someone other than the original developer to pick up the code and work on it with confidence.

This all results in improved customer confidence in the product and better tolerance for any problems that do occur because they know that they can be quickly resolved.

New Features

Code that is well structured is much easier to modify to add new features to. And just like the maintenance situation, there is less likelihood of such changes introducing new problems into either the new or the existing code. This all helps to get the product out to market that much quicker and earning revenue.

The Bottom Line

If you are a commercial programmer, that is, it’s your job, your work earns the business that you work for, the money that pays your wages. The quicker you can develop new code or fix existing code directly affects the companies business results and therefore your earnings.





Categories: Coding, Style

ISPF Edit ‘Count’ macro

August 22, 2017 Leave a comment

Just a little macro I put together to count the number of occurrences of a string in a file when editing it.

/* rexx */ 
if text = '' then do 
 say 'Nothing to search for. Enter text to search for ith cmd' 
 return 0 
address isredit "find all "text 
address isredit "(num,lines) = FIND_COUNTS" 
if num > 1 then s='s' 
if lines > 1 then ls='s' 
if lines > 0 then on = ' on 'lines' line'ls 
say 'Found 'num' occurance's' of 'text||on

To run it, just type count followed by the string to search for, and any other parameters such as the column number on the command line when in edit and press enter. E.G.

COUNT ‘some string’







Categories: Uncategorized