Arithmetisch-Logische-Einheit

1,108,802. Electric digital calculators. INTERNATIONAL BUSINESS MACHINES CORPORATION. 16 March, 1965 [6 April, 1964], No. 10973/65. Heading G4A. In an electronic data processor, a machine condition determining a conditional branch is represented by a comination of the states of two or more bi-stable circuits. Instructions are normally selected by a counter but in the case of a branch, the address of the next instruction is given in the branch instruction, either as a single field or as three fields (base, index and displacement) to be added together. The branch instruction contains four bits which are compared with four (comprising only one 1) obtained from decoding two bits in a programme status word partially controlling operations, to determine if the condition is satisfied. An unconditional branch may be obtained by having the four bits in the branch instruction word all 1's. The condition relates to the result of the instruction preceding the branch instruction and the significance of a particular pattern of four bits depends on the nature of the preceding instruction. The Specification repeats some subject-matter of Specification 1,108,801 which is referred to.