The telephone gave us a long-distance voice. Radio took away the wires; television added pictures. But the real revolution occurred well before all of that: In one fell swoop, the telegraph allowed messages to travel not at the pace of a man on a pony or a speeding locomotive but at the velocity of an electron. In like fashion, the colossal library of Netflix may be impressive, but the videocassette recorder was a revolution. The rest, which a reeling industry is still trying to sort out, is digital gravy.

It is orthodoxy to say that television, in 2015, is in the midst of radical change. We can watch a bewildering amount of material at will, and portable devices let us do so outside of the home. What’s more, a significant increase of highbrow programming now defies the old idea of television as the “idiot box.” Yet for all the advances that online distribution and digital technologies have brought, the real revolution came about 30 years ago. By 1985, viewers could see a show after it had aired, and their choices had increased greatly. They could watch a hand-held TV at the beach, and some shows had already started to exhibit serious artistic ambitions.

Image Blockbuster Video, MTV and the programs “Moonlighting” and “Hill Street Blues” were all part of the TV revolution.

The heart of today’s transformation of television is storage. Viewers have access to vast quantities of programming, according to their tastes and schedules, stored on DVRs, DVDs, on-demand cable and satellite channels, and online services. Not so very long ago, if you wanted to see “Citizen Kane,” you had to hope for a retrospective screening at an art house, or wait until it played on television. In 1977, the tens of millions of people who saw “Roots” had no choice but to stay home for eight consecutive nights and watch the broadcast on ABC.