Program.
What is a computer program?
It is a set of instructions, to be obeyed by a computer. The instructions are mostly arranged in sequence, but selection and repetition are other essential compositional structures.
In looking for a Gaelic term for "computer program", I ask myself what else is like it? What else consists of a series of instructions to be followed? The best I can come up with is a recipe, or a prescription. With the recipe analogy, the recipe is the program, the cook is the computer, the person originating the recipe is the computer programmer.
The Gaelic for "recipe" is "oideas". I think this is quite suitable for a computer program. The most common meaning of "oideas" is "training". And when you supply a computer with a program, you are indeed training it, or programming it, so that it now can perform the task elaborated in the program. Moreover, in Dwelly's Gaelic dictionary, under a cross-reference to "oideachd", we find the meaning "occult science", which I like to think captures one view of computers and programming!
More importantly, we can construct a very satisfactory terminological field around "oideas" meaning "program". And of course "oideas" itself may be expanded to "ríomh-oideas" in any case where the context is not clearly established as computation. Derived terms may include:
"Clár" (FR 296: clár, ríomhchlár) is an unsuitable term for "computer program". Not only is it semantically useless — its basic meaning is a wooden board, and by extension, a smooth flat surface — but worse, there are many computing artifacts which are much more "clár"-like than a program is: desktop, keyboard, screen, disc, menu, etc. In Scotland, "clár" is used for some of these, while the word used for "program" is "prògram". In Ireland, I would regard "prógram" as an acceptable second choice to "oideas" and greatly preferable to "clár".