Magnetic Core Memory's

Section Six - Relation between the Decimal and Binary Codes

## Relation between the Decimal and Binary Codes

It was stated earlier that any of the ten symbols 0, 1, 2, 3, 4, 5, 6, 7, 8 and 9 of the decimal notation can he represented in the binary code by different combinations of the conditions 0 and 1 in a group of four elements. This can be simply explained by reference to Fig. 8 which shows the four elements.

Any element in the condition 0 is considered as equivalent to. the decimal symbol 0. An element in condition 1 corresponds to the decimal symbol1,2, 4 or 8 according to its position in the group. In mathematical terms. the elements themselves, reading from right to left in Fig. 8, when in the 1 condition correspond to 2o(=1), 2x10(1) (=2), 2x2(=4) and 2(3) (=8). In the 0 condition any element corresponds to 0, as previously stated. The actual decimal digit represented by a group of four elements is obtained by adding the four decimal symbols which the four elements represent.The table below indicates how any decimal digit (0 to 9) can be expressed in the binary code with four elements (,bits').

Fig8 - Table of the binary-coded decimal digits

In a magnetic memory, the four elements required to represent a decimal digit are not mounted side by side as-in Fig. 8, but stacked one above another as shown in Fig. 9. Here, reading upward from the lowest element (A) in the stack, elements in the 1 condition will represent 1, 2, 4 add 8. These four elements occupy corresponding positions in four matrix planes. It is important to remember that in order to store decimal numbers in the binary code a memory requires at least four matrix planes.

Fig9

The X- and Y-wires of the stack of four elements are so connected that one X-pulse and one Y-pulse will influence all four elements required to represent a decimal symbol.

Matrix plane being wired.

Threading the wires of a core-mass memory containing some 130,000(30 mil) cores.