Three hobgoblins, if not more, scuttle the illusion that computers are magic: entropy wrecks the hardware, information's continually changing shape makes software obsolete, and engineers (hardware and software) are fallible. In the typical portrayal of magic, it doesn't have these problems. Imagine if a magus had to contend with them:
- Entropy. Eventually, a wand would stop sending out sparks like it used to. Worse, it might start short-circuiting. Quests for hidden enchanted objects would be pointless, since those objects would long since have lost all effectiveness. Ancient books would fall apart, of course. Potions would go bad (or go good or go neutral, whatever). Flying brooms would start to give out, hopefully not during a high flight, and develop the same troubles as other wooden things, like splinters (ouch!). The power factor would demand special attention since magical actions expend so much energy, particularly in transformations of matter. No matter what the source of magical power is, that source wouldn't be inexhaustible (even if it's human thought/concentration/imagination/emotion that would still imply that each application leaves the person's consciousness reduced somehow). Anything that can operate while disconnected from a magical power source would need periodic recharging, but a "standby" or "hibernate" mode would help. Related to the power factor is the dissipation factor. The efficiency of magicked widgets wouldn't be absolute, resulting in a certain amount of magic leakage. Presumably, the leakage wouldn't be desirable, and overuse might produce an (apocalyptic?) overheated state. On the other hand, purposely approaching this limit for the sake of performance might be reasonable if done conscientiously. One would hope that the manufacturer would be overly conservative in estimating the threshold.
- Information malleability. First of all, spells would be much more specific than commonly assumed. The desired effects represent a finely-detailed confluence of information; else the vivified brooms will never stop carrying water in buckets from here to there, which would be an exceedingly serious bug, eh? The spell must precisely communicate its intent because the information must come from somewhere, and the information to produce a specified effect is always conserved. This means that the spell to transform someone into a newt is different than the spell to transform someone into a toad. And what if needs change in the future? For instance, now the toad must be able to retain the power of speech? Well, with any luck, the original spell-writer will have accommodated that by making the preserved human attributes configurable through additional optional spell clauses--if the spell-writer wasn't enough of a soothsayer to predict that need, then a new, complex spell is required. As for the toad, if the human's vocabulary wasn't extracted and stored just in case during the process of the first transformation, then the sorcerer has no other option than starting again with a different subject. Then there's the situation of a kitchen spell that automatically washes pans with steel wool. That's great until buying a Teflon skillet. A golem guard under instructions to pulverize uninvited visitors, like pushy salespeople, may seem great until it mashes your next-door neighbor, who came by to drop off the newspapers that were delivered during your vacation. A spell to create one hundred units of currency out of air is fairly convenient in the U.S. (your 15% interest rate credit card doesn't count), but chanting the same spell in Japan is not.
- Human fallibility. Oh, sure, tales of less-than-stellar mages aren't hard to find, and neither are tales of inadvisable attempts at something poorly understood. However, it's relatively unusual to find accounts of a normal practitioner who has a level 5 certification and occasionally fails to perfectly complete a level 3 incantation. Oops, the caster slurred a few words. When he or she was visualizing what should happen, concentration dropped for a moment or the envisioned vehicle's interior wasn't considered. Too many drops of the sixth ingredient went in, and now the concoction is worthless. The crystal ball is a tad oblong, causing everything to look horizontally stretched. A Trinket of Power has some flaws that necessitate tapping it several times whenever it intermittently stops functioning. When the spellbook was copied, several errata crept in. Some unnoticed iocaine powder was on the witch's fingers when she was stirring the cauldron, and consequently the antidote mysteriously acted like a poison. Instructions for the bewitching of the shoes didn't explicitly state that the shoes had to be made by leprechauns. Wearing an Invisibility Anklet or Invincibility Brooch is fine, but wearing both at once causes problems during the night of the 1st quarter of the moon. And the Bow of Elvish Accuracy only is compatible with FairyGenuine arrows, although any Crossbow of Standard Aim should at least wing the target with arrows that claim to match the Warlock Council's Archery Dictates.