The ABC used for heap memory. Like the current RAM memory required for a period of refresher to remember its state code. Atanasoff believe the use of different technologies for the construction of the main memory such as magnetic memory, vacuum tubes and capacitors to store each bit of memory. Finally the cost per bit and the performance made him decide on the use of capacitors. The main memory consisted of drums Cadiz ( ‘Counter abbacy’) and KA ( ‘Keyboard abbacy’.) Drums CA and KA are identical. Have thirty-two bands along the length of the drum. Each band has sixty physical position, of which fifty-containing capacitors mounted radially around the drum. Each capacitor stores one bit and each band is an element of the vector. The two additional bands are spares in case of failure of a capacitor.
The terms’ counter ‘and’ keyboard ‘are reminiscent of the original concepts of the mechanical adding machine in which a control unit adding the cumulative total, and the values entered through the keyboard or’ keyboard ‘are added or subtracted to this amount. At present, the dynamic memory based capacitors printed on silicon chips continues to offer the best cost and performance. This memory was organized into two banks of thirty-two words each. Two of these words were spare parts. As each word fifty bits of mantissa of a still more, the total storage capacity of three thousand two hundred and sixty-four bits. The banks were used as records for the arithmetic unit. Each bank of registers reside in a separate cylinder.