Paper tape
Programs stored as holes in a strip of paper — cheaper than punched cards and impossible to reorder.
The technique came from telegraphy, where five-hole tape carried Baudot code long before computers existed. Computer machinery used eight holes per row, one per bit of an ASCII character, plus a row of small sprocket holes for the feed wheel. The tape was punched on a teletype or a separate punch and read back optically or mechanically. Unlike a deck of cards it cannot be rearranged: correcting a mistake meant a new tape, or scissors and splicing tape.
The medium carried everything from Colossus input to the first microcomputer software. Microsoft's Altair BASIC was distributed on paper tape in 1975 and copied so freely at hobby club meetings that Bill Gates wrote his irate open letter to hobbyists arguing that somebody had to pay for software.