1. A multi-cycle control system for causing a series of events to occur in sequence and capable of altering said sequence, comprising: storage means for storing a plurality of coded instruction words at a corresponding plurality of addresses, each word comprising a first and a second portion; address register means coupled to the storage means for providing an address to select a coded instruction word, said address register means being capable of incrementing the address provided in successive operations of the system by a predetermined increment and also capable of modifying the address in a non-incrementing mode; decoding means coupled to the storage means and capable of generating operating code signals including conditional and unconditional branch signals from predetermined signal combinations of said first portion of each coded instruction word; second register means coupled to the address register means and to the storage means for receiving said second portion of each coded instruction word from said storage means under control of an operating code signal from the decoding means to provide part of a new address and presenting an address modifying code which corresponds to said second portion to the address register means to cause a modified address to be provided to the storage means by the address register means during a subsequent operation of the system; and branch control means coupled to and controlled by the decoding means and coupled to the address register means for controlling whether or not an address modifying code is loaded into the address register means during a given operation, said branch control means including indicator means settable during a first cycle by a signal from a selected origin, and also including logic means responsive to the condition of the indicator means and to conditional and unconditional branch signals, and capable of controlling said second register means to determine whether or not a modified address is provided to the storage means by the address register means during a subsequent cycle of operation of the system.