Fundamentals of Communications and Networking, 3rd Edition

Application Architectures

In the early days of computing, users ran an individual program on large, expensive mainframe computers to accomplish a specific task—general purpose applications didn’t exist. A program’s instructions were either manually entered via a computer console or stored on cards with holes punched in them. These punch cards made early programming life easier by relieving computer operators from having to enter CPU instructions one at a time. Early computer programs had specific uses and almost no recognizable user interface. The computer operator would load a program’s instructions along with its initial data, and then the program would run and hopefully produce some usable output.

As the value of computers began to be appreciated ...