IBM G24-1377-0 1401 dataFlow free download

File name G24-1377-0_1401_dataFlow.pdf

1401 DATA PROCESSING SYSTEM BULLETIN 1401 DATA FLOW New, more efficient programming techniques for the age on one of the wires running through the center of IBM 1401 Data Processing System are being developed the core. This voltage is recognized as a bit. as the programming knowledge and the experience Information is always read into core storage during level on the system increases. This manual presents a the late haH of a cycle. If the information that was read semi-detailed data How explanation of every 1401 oper- out of a storage location is to be retained in the same ation. This approach should assist both the new, and location, it is read back into that location from one of the more experienced, programmer with his 1401 pro- the registers during the late haHof the read-out cycle. gramming effort. The 1401 system also makes use of this core-storage Each operation is presented in the form of a data- operation to perform the system's arithmetic opera- How diagram. The path that the data takes during an tions. Two areas are alternately read out a position at a operation is graphically presented along with a written time, added together, and the sum stored in the last explanation of the steps involved. The internal-parity position read out. This is called add-to-storage logic, and validity-checking operations are also presented, and it eliminates the need for special-purpose accumu- along with a list of the console lights that will be ON in lators or counters. Because any group of storage posi- the event of a parity or validity check condition. tions can be used as an accumulating field, the capacity for arithmetic functions is not limited by a predeter- Data Flow mined number of counter positions. DATA LINES AND INHIBIT DRIVE The data How of an IBM 1401 Data Processing System is schematically shown in Figure 1. The How paths used The data-How paths shown in Figure 1 as single lines are initially specified by the stored program instruc- are actually eight lines (4 digit, 2 zone, 1 word mark, tions. These instructions tell the system what areas to and 1 check). The lines leading to the inhibit drive are read out of, and what areas to read into. The internal called inhibit lines because they inhibit, or prevent, the circuitry of the system then carries out the specified setting of cores unless activated by the presence of a data movement. The various component areas of the bit of information. Information being sent into core system ar