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dc (desk calculator) is a cross-platform reverse-Polish calculator which supports arbitrary-precision arithmetic. [1] It was written by Lorinda Cherry and Robert Morris at Bell Labs. [2] It is one of the oldest Unix utilities, preceding even the invention of the C programming language. Like other utilities of that vintage, it has a powerful set ...
The opcode input is a parallel bus that conveys to the ALU an operation selection code, which is an enumerated value that specifies the desired arithmetic or logic operation to be performed by the ALU. The opcode size (its bus width) determines the maximum number of distinct operations the ALU can perform; for example, a four-bit opcode can ...
Many arithmetic and logic operations set, clear or complement these flags depending on their result. The comparison cmp (compare) and test instructions set the flags as if they had performed a subtraction or a bitwise AND operation, respectively, without altering the values of the operands.
This is a list of POSIX (Portable Operating System Interface) commands as specified by IEEE Std 1003.1-2024, which is part of the Single UNIX Specification (SUS). These commands can be found on Unix operating systems and most Unix-like operating systems.
bc first appeared in Version 6 Unix in 1975. It was written by Lorinda Cherry of Bell Labs as a front end to dc, an arbitrary-precision calculator written by Robert Morris and Cherry. dc performed arbitrary-precision computations specified in reverse Polish notation. bc provided a conventional programming-language interface to the same capability via a simple compiler (a single yacc source ...
A common example is the Data General Nova, which was a 16-bit design that performed 16-bit math as a series of four 4-bit operations. 4-bits was the word size of a widely available single-chip ALU and thus allowed for inexpensive implementation. Using the definition being applied to the 68000, the Nova would be a 4-bit computer, or 4/16.
The two basic types are the arithmetic left shift and the arithmetic right shift. For binary numbers it is a bitwise operation that shifts all of the bits of its operand; every bit in the operand is simply moved a given number of bit positions, and the vacant bit-positions are filled in.
They use the Duplex Multi Environment Real Time operating system which was renamed UNIX-RTR (Real Time Reliable) in 1982. The Data Manipulation Unit (DMU) provides arithmetic and logic operations on 32-bit words using eight AMD 2901 4-bit-slice ALUs. [9] The first 3B20D is called the Model 1.