To answer your question (everyone is asking oneself before an upgrade): which applications the update to MacOS X will break?

There is no professional, nor any easy answer to this question (this isn't typical of MacOS X, it is nearly the same situation on any OS):

• Apple doesn't provide a database of known incompatabilities,

• most application developpers don't provide a database of known incompatibilities.

Hence it is up to the user to take this risk and test by himself.

Here is my personnal advice on how to proceed starting from a Mac running Leopard.

1. Use an external disk (rather a new one) and make a clone copy of your actual internal disk on it. For this task use Carbon Copy Cloner 3.5.7 (which is the last one compatible with Snow Leopard).

2. Download Yosemite combo update.

3. Install it on your external disk.

4. Boot from your external disk now running Yosemite 10.10.5.

5. For each application important for your father to work,

   check if it is running correctly

   if it doesn't, find if the application editor provides a compatibility support (as Carbon Copy Cloner does professionnaly) and download the appropriate update. Beware, in some cases this search for the compatible version will be a failure. This is the reason why some editors don't like to advertise this compatibility matrix and let the user discover it on his own.

   continue with next application.

If you follow this receipe, your original disk is still hosting Snow Leopard. It is a de facto backup you can schwitch back to as quickly as switching the boot disk (~5 minutes).

6. Run on your external disk hosting Yosemite and its set of applications (kept as is or updated or abandonned) for a few days (I advise to check it for a week) with all these applications, to detect all the other possible incompatibilities.
7. If the state reached is OK, do the reverse of step 1.: clone your external disk onto your internal one, and switch on it as the boot disk.

To answer your question (everyone is asking oneself before an upgrade): which applications the update to MacOS X will break?

There is no professional, nor any easy answer to this question (this isn't typical of MacOS X, it is nearly the same situation on any OS):

• Apple doesn't provide a database of known incompatabilities,

• most application developpers don't provide a database of known incompatibilities.

Hence it is up to the user to take this risk and test by himself.

Here is my personnal advice on how to proceed starting from a Mac running Snow Leopard.

1. Use an external disk (rather a new one) and make a clone copy of your actual internal disk on it. For this task use Carbon Copy Cloner 3.5.7 (which is the last one compatible with Snow Leopard).

2. Download Yosemite combo update.

3. Install it on your external disk.

4. Boot from your external disk now running Yosemite 10.10.5.

5. For each application important for your father to work,

   check if it is running correctly

   if it doesn't, find if the application editor provides a compatibility support (as Carbon Copy Cloner does professionnaly) and download the appropriate update. Beware, in some cases this search for the compatible version will be a failure. This is the reason why some editors don't like to advertise this compatibility matrix and let the user discover it on his own.

   continue with next application.

If you follow this receipe, your original disk is still hosting Snow Leopard. It is a de facto backup you can schwitch back to as quickly as switching the boot disk (~5 minutes).

6. Run on your external disk hosting Yosemite and its set of applications (kept as is or updated or abandonned) for a few days (I advise to check it for a week) with all these applications, to detect all the other possible incompatibilities.
7. If the state reached is OK, do the reverse of step 1.: clone your external disk onto your internal one, and switch on it as the boot disk.

To answer your question (everyone is asking oneself before an upgrade): which applications the update to MacOS X will break?

There is no professional, nor any easy answer to this question (this isn't typical of MacOS X, it is nearly the same situation on any OS):

• Apple doesn't provide a database of known incompatabilities,
• most application developpers don't provide a database of known incompatibilities.

Hence it is up to the user to take this risk and test by himself.

Here is my personnal advice on how to proceed starting from a Mac running Leopard.

1. Use an external disk (rather a new one) and make a clone copy of your actual internal disk on it. For this task use Carbon Copy Cloner 3.5.7 (which is the last one compatible with Snow Leopard).

2. Download Yosemite combo update.

3. Install it on your external disk.

4. Boot from your external disk now running Yosemite 10.10.5.

5. For each application important for your father to work,

   check if it is running correctly

   if it doesn't, find if the application editor provides a compatibility support (as Carbon Copy Cloner does professionnaly) and download the appropriate update. Beware, in some cases this search for the compatible version will be a failure. This is the reason why some editors don't like to advertise this compatibility matrix and let the user discover it on his own.

   continue with next application.

If you follow this receipe, your original disk is still hosting Snow Leopard. It is a de facto backup you can schwitch back to as quickly as switching the boot disk (~5 minutes).

6. Run on your external disk hosting Yosemite and its set of applications (kept as is or updated or abandonned) for a few days (I advise to check it for a week) with all these applications, to detect all the other possible incompatibilities.
7. If the state reached is OK, do the reverse of step 1.: clone your external disk onto your internal one, and switch on it as the boot disk.

To answer your question (everyone is asking oneself before an upgrade): which applications the update to MacOS X will break?

There is no professional, nor any easy answer to this question (this isn't typical of MacOS X, it is nearly the same situation on any OS):

• Apple doesn't provide a database of known incompatabilities,

• most application developpers don't provide a database of known incompatibilities.

Hence it is up to the user to take this risk and test by himself.

Here is my personnal advice on how to proceed starting from a Mac running Leopard.

1. Use an external disk (rather a new one) and make a clone copy of your actual internal disk on it. For this task use Carbon Copy Cloner 3.5.7 (which is the last one compatible with Snow Leopard).

2. Download Yosemite combo update.

3. Install it on your external disk.

4. Boot from your external disk now running Yosemite 10.10.5.

5. For each application important for your father to work,

   check if it is running correctly

   if it doesn't, find if the application editor provides a compatibility support (as Carbon Copy Cloner does professionnaly) and download the appropriate update. Beware, in some cases this search for the compatible version will be a failure. This is the reason why some editors don't like to advertise this compatibility matrix and let the user discover it on his own.

   continue with next application.

If you follow this receipe, your original disk is still hosting Snow Leopard. It is a de facto backup you can schwitch back to as quickly as switching the boot disk (~5 minutes).

6. Run on your external disk hosting Yosemite and its set of applications (kept as is or updated or abandonned) for a few days (I advise to check it for a week) with all these applications, to detect all the other possible incompatibilities.
7. If the state reached is OK, do the reverse of step 1.: clone your external disk onto your internal one, and switch on it as the boot disk.