4. Vacuum Tube Memory
Vacuum tubes were used to provide temporary data storage (memory) in early digital computers. Pins on the tube’s base were connected via wires to internal elements arranged in grids on cathode, collector, insulator, and read-write sheets. Multiple miniature electrical circuits formed logical gates that held bits of data (1 or 0). A 16x16 arrangement could store and read back 256 bits of data. Some tubes with multiple stacked sheets could store 4096 (4 kilobits) of data. The data in memory was erased when the tube was powered off.
Punched Cards
Early digital computers used punched cards for data transfer and storage. The punched card technology dates back to Herman Hollerith’s patent of 1884. Each card had 80 columns arranged in 12 rows. The punches in each column coded for an alphanumeric character. The rightmost 8 columns were sometimes reserved to assign card sequence numbers, and if so up to 72 data characters could be coded for in one card. The characters could be printed on the cards, so humans as well as computers could read them. The cards were made of heavy, stiff paper, and were 3-1/4 inch x 7-3/8 inch in size.