Fig. 7.1.4 shows the SDLC.

Fig. 7.1.4 The SDLC.

The SDLC is sometimes called the “waterfall” approach to the development of systems.

Disk Technology

Into this fray at about the time of structured development of systems came the disk
storage device. With disk storage, data could be accessed directly. Prior to the advent of
disk storage, data had been stored on magnetic tape files. Even though magnetic tape files
could hold a lot of data, all the data on the magnetic tapes had to be accessed
sequentially. In order to find a single record, you had to process the entire file.

In addition, magnetic tape files were notoriously unreliable for the long-term storage of

Chapter 7.1: The Operational Environment: A Short History