9. Legacy Systems

• Old software systems were implemented with third generation programming languages that used procedural programming concepts.

• These systems are called legacy systems.

• Procedural programming involves writing a series of instructions in sequence:

  • all input data from keyboard or disk drive is read into "globally" shared memory;

  • the "next" computer instruction follows "current" instruction, occasionally passing control to another instruction somewhere in memory;

  • all output data is written to console screen, printer, or disk drive from the shared memory.

• Procedural programming is also known as structured code.