Start – Pressing this key with the computer in Manual mode switched the computer to Automatic mode (causing the computer to begin executing at the address in the program counter). Stop-SIE – Pressing this key with the computer in Automatic mode switched the computer to Manual mode when the currently executing instruction completes. Pressing this key with the computer in Manual mode switched the computer into Automatic mode for one instruction. Instant Stop-SCE – Pressing this key with the computer in Automatic mode switched the computer into Automatic/Manual mode at the end of the current memory cycle. Pressing this key with the computer in Manual or Automatic/Manual mode switched the computer into Automatic/Manual mode and executed one memory cycle. For program debugging there were the buttons labeled Save & Display MAR. Save – Pressing this key with the computer in Manual mode saved the program counter into another register in the MARS core memory and activated Save mode. When a Branch Back instruction was executed in Save mode, it copied the saved value back to the program counter (instead of copying the return address register as it normally did) and deactivated Save mode.
Start – Pressing this key with the computer in Manual mode switched the computer to Automatic mode (causing the computer to begin executing at the address in the program counter). Stop-SIE – Pressing this key with the computer in Automatic mode switched the computer to Manual mode when the currently executing instruction completes. Pressing this key with the computer in Manual mode switched the computer into Automatic mode for one instruction. Instant Stop-SCE – Pressing this key with the computer in Automatic mode switched the computer into Automatic/Manual mode at the end of the current memory cycle. Pressing this key with the computer in Manual or Automatic/Manual mode switched the computer into Automatic/Manual mode and executed one memory cycle. For program debugging there were the buttons labeled Save & Display MAR. Sav.e – Pressing this key with the computer in Manual mode saved the program counter into another register in the MARS core memory and activated Save mode When a Branch Back instruction was executed in Save mode, it copied the saved value back to the program counter (instead of copying the return address register as it normally did) and deactivated Save mode.