The Control Element contains two six bit registers and several miscellaneous flip-flops. The latter deal with indexing, indirect addressing, memory control, etc. The six bit registers are:
Instruction Register
The Instruction Register receives the first six bits of the Memory Buffer Register during the cycle which obtains the instruction from memory (cycle zero). This information is the primary input to the Control Element.
Program Flags
The six Program Flags act as convenient program switches. They are used to indicate separate states of a program. The program can set, clear, or sense the individual flip-flops. The program can also sense or make the state "All Flags ZERO." They can also be used to synchronize various input devices which occur at random times (see [Input-Output], [Typewriter Input]).
Three toggle switch registers are connected to the Central Processor (see [Manual Controls]).
Test Address
The fifteen Test Address Switches are used to indicate start points and to select memory registers for manual examination or change.