microcode
- Microcodes are non-addressable but modifiable programs. They can be installed and modified by the computer user, with the modifications occurring in Programmable Read Only Memory( PROM) or EPROM.
- InCICS microcomputers, Customer Information Control System ( CICS), a microcode breaks down the complex instructions of a program into a sequence of elementary instructions. Such a sequence of microinstructions is permanently stored in a memory area that is not addressable by programs and that supports specific process functions.
- In the case of systems and system components, this is the innermost machine code. The microcode resides in ROM memory, is used to control hardware units and interfaces with the operating system.