Overview
The vehicle relies on computerized control and monitoring for successful performance.

Software
DPS software is divided into two major groups: system software and applications software.

General-Purpose Computers
Five identical computers aboard the orbiter control vehicle systems.

Mass Memory Units
Computing functions for all mission phases requires about 400,000 words of computer memory.

Multifunction CRT Display System
Displays on the flight deck allow onboard monitoring of systems, software processing and manual control for crew data and software manipulation.

Master Timing Unit
The GPC complex requires an accurate time source because its software uses GMT to schedule processing.

Computer Data Bus Network
Network is divided into specific groups that perform specific functions.

Multiplexers/Demultiplexers
DPS MDMs convert and format serial digital GPC commands into separate commands for various vehicle system hardware.

Master Events Controllers
Send signals to arm and safe pyrotechnics during SRB/ET separation.

Data Bus Isolation Amplifiers
Interfacing devices for the GSE/LPS and SRB MDMs.

Backup Flight Control The fifth GPC, loaded with different software, provides backup in case primary GPCs fail.